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Author: One Health Students

ONE HEALTH: INTERDISCIPLINARY APPROACHES TO PEOPLE, ANIMALS AND THE ENVIRONMENT
Fall 2008
Gretchen Kaufman, DVM
Cummings School of Veterinary Medicine at Tufts University

1. Human Health Perspective – Student Work

1.1. Disciplinary Gaps and Research Questions from the Human Health Perspective

  • How do human health risks and benefits differ between organic and conventional dairy farms in New England?

    • Method: A retrospective cohort study comparing medical records of people in close proximity to primarily organic dairy farms with people in close proximity to primarily conventional dairy farms and comparing both with people from an appropriate control community who are not in close proximity to any farms but otherwise have similar characteristics.

    • Method: A prospective or retrospective study comparing the medical records of farmers on organic versus conventional dairy farms.

    • Method: Surveys of the health and perceived Quality of Life individuals living near organic dairy farms compared to individuals living near conventional dairy farms.

    • Method: Surveys of the health and perceived Quality of Life farmers on organic dairy farms compared to farmers on conventional dairy farms.

    • Hypothesis: Health risks and benefits will differ between individuals living in communities near organic farms and those near conventional farms as will risks and benefits between farmers working on organic versus conventional dairy farms with the majority of risks occurring on/near conventional farms and the majority of benefits occurring on/near organic farms. Quality of life will be better for both individuals living near organic farms as well as the farmers living on them.

  • How similar are the organic and conventional dairy farming situations in New England to farming systems throughout North America and the rest of the world?

    • Method: Work with the New England farming industry to identify common and best practices for the region in both organic and conventional farms. Do the same with the rest of North America and other relevant regions (e.g., Europe, Australia, New Zealand). Compare the findings from each.

    • Method: Perform a meta-analysis on all research specific to New England farming methods separating findings into organic and conventional as well as effects on agricultural, animal, environmental, and human health. Perform similar meta-analyses for North America and other frequently studied farming systems and compare the results with the New England findings.

    • Hypothesis: Conventional farming will be vastly different in New England versus other areas of North America due to the trend towards smaller conventional farms. Some specific practices may be quite similar while others may vary vastly between organic and conventional farms in New England versus other regions.

  • How prevalent are manure pits and lagoons in New England dairy systems? Do these differ between New England organic and conventional dairy farms?

    • Method: Survey New England farms on their use of manure pits and lagoons and categorize use into conventional or organic.

    • Hypothesis: Organic farms may be less reliant on the use of manure pits and lagoons.

  • Are there differences in confined space risks on organic versus conventional farms?

    • Method: Survey New England farms about the number of confined spaces on their property and categorize findings into conventional versus organic.

    • Method: Examine medical reports of confined space incidents in New England and compare number of incidents on conventional farms per the number of conventional farms versus number of incidents on organic farms per the number of organic farms.

    • Hypothesis: No difference will be found when controlling for the greater number of conventional farms to organic farms.

  • Are mechanical risks (e.g., injury caused by farm machinery) any different between organic and conventional farms?

    • Method: A retrospective cohort study comparing medical records of mechanically induced morbidity and mortality of farmers on primarily organic dairy farms with farmers on primarily conventional dairy farms.

    • Hypothesis: Fewer medically reported mechanically induced incidents occur on organic dairy farms versus conventional dairy farms.

  • Are respiratory illnesses in dairy cattle caused by the same mechanisms as respiratory illness/compromise/disease in farmers?

    • Method: Compare veterinary/animal health research on respiratory disease in cattle with similar research in dairy farmers. Measure both exposures in a case-control study.

    • Method: Compare respiratory tissue of infected cattle with respiratory tissue of infected humans to identify unforeseen irritants.

    • Hypothesis: Chronic respiratory diseases in both cattle and dairy farmers will be initiated by similar exposures.

  • Are noise exposures resulting in hearing loss any different between organic and conventional farms?

    • Method: A retrospective cohort study comparing medical records of hearing loss of farmers on primarily organic dairy farms with farmers on primarily conventional dairy farms.

    • Method: Survey decibel levels on organic dairy farms and compare findings with decibel levels on conventional dairy farms.

    • Method: Study the actual use of Personal Protective Equipment to prevent hearing loss on organic dairy farms versus conventional dairy farms.

    • Hypothesis: Hearing loss will be less dramatic to farmers from organic dairy farms versus conventional dairy farms and use of Personal Protective Equipment will be higher in high risk situations on organic dairy farms.

  • Do allergy and asthma rates and other respiratory diseases and disorders differ with both farmers and the community on and near organic versus conventional farms?

    • Method: A retrospective cohort study comparing medical records of allergies and asthma of farmers on primarily organic dairy farms with farmers on primarily conventional dairy farms.

    • Method: A retrospective cohort study comparing medical records of allergies and asthma of people living near primarily organic dairy farms with people living near primarily conventional dairy farms.

    • Method: Surveys of self-proclaimed respiratory symptoms of farmers on organic versus conventional farms.

    • Method: Surveys of self-proclaimed respiratory symptoms of people living near primarily organic versus people living near primarily conventional farms.

    • Method: Case-control study comparing allergen response to farmers on organic farms versus farmers on conventional farms.

    • Method: Case-control study comparing allergen response to people living near primarily organic farms versus people living near primarily conventional farms.

    • Hypothesis: There will be no difference between the allergy and asthma rates of farmers on organic farms versus conventional farms, however, farmers on more hygienic farms will have fewer allergies and rates of asthma than farmers on less hygienic farms.

    • Hypothesis: There will be no difference between the allergy and asthma rates of people living near primarily organic farms versus people living near primarily conventional farms.

  • Do pathogen levels differ between conventional and organic farms in New England?

    • Method: Study comparing pathogen levels in bulk tank milk on organic and conventional farms.

    • Hypothesis: Organic farms will have a lower isolation rate of pathogens in their bulk tank milk because their cows are less pushed to produce milk.

1.2. Terms

Amlification
Rapid replication of genetic material.

Apnea
Temporary suspension of breath.

Biofilm
A resilient layer of microorganisms coated by an extracellular matrix; usually adheres to surfaces.

Bovine Somatatropin (bST, BST
a resilient layer of microorganisms coated by an extracellular matrix; usually adheres to surfaces.

Bronchospasm
A sudden, rapid constriction of the muscles in the walls of the bronchioles of the respiratory tract.

Cervical
In people, the seven vertebrae of the neck.

Chronic bronchitis
Chronic bronchitis is not necessarily caused by infection and is generally part of a syndrome called chronic obstructive pulmonary disease (COPD); it is defined clinically as a persistent cough that produces sputum (phlegm) and mucus, for at least three months in two consecutive years. (Wikipedia.org)

Chronic obstructive pulmonary disease (COPD)
Chronic obstructive pulmonary disease (COPD) is a disease of the lungs in which the airways become narrowed. This leads to a limitation of the flow of air to and from the lungs causing shortness of breath. In contrast to asthma, the limitation of airflow is poorly reversible and usually gradually gets worse over time (Wikipedia.org). One form of COPD particularly related to dairy farming is chronic bronchitis.

Dose-response
The Dose-response relationship describes the change in effect on an organism caused by differing levels of exposure (or doses) to a stressor (usually a chemical). This may apply to individuals (e.g., a small amount has no observable effect, a large amount is fatal), or to populations (e.g., how many people are affected at different levels of exposure). (wikipedia.org)

Gastroenteritis
Inflammation of stomach and intestines; common symptoms include nausea, diarrhea, vomiting and cramps.

Methemoglobinemia
A condition caused by higher than normal methemeglobin in the blood that may be linked to drinking water with high levels of nitrates. The condition is well known in infants under 5 months of age primarily in rural areas reliant on well water.

Quality of Life (QoL
In public health and in medicine, the concept of health-related quality of life refers to a person or group's perceived physical and mental health over time. Physicians have often used health-related quality of life (HRQOL) to measure the effects of chronic illness in their patients to better understand how an illness interferes with a person's day-to-day life. Similarly, public health professionals use health-related quality of life to measure the effects of numerous disorders, short- and long-term disabilities, and diseases in different populations. Tracking health-related quality of life in different populations can identify subgroups with poor physical or mental health and can help guide policies or interventions to improve their health. (CDC.gov)

Reservoir
An organism in which a parasite that is pathogenic for some other species lives and multiplies usually without damaging the host. (M&W)

Thoracic
In people, the 12 vertebrae of the middle and upper back most of which are associated with attached ribs.

URI
Upper respiratory infection.

Zoonosis
A disease that can be transmitted between animals and humans.

1.3. Stereotypes about the Human Health Perspective

Stereotypes we believe that other disciplines may hold for human health include

  • Only interested in people (Often true)

  • Data focused/driven (Often true)

  • Biggest egos (False, but understandable)

  • Treatment focused (False but understandable). This one is dependent on whether other groups understand the purpose of public health or whether they perceive human health disciplines to be human health practitioners

  • Only care about physical health (False, but understandable. Many focus on mental/social health too)

1.4. Human Health Perspective Presentation Materials

1.5. Human Health Perspective Annotated Bibliography

Adhikari A. Reponen T. Lee SA. Grinshpun SA. Assessment of human exposure to airborne fungi in agricultural confinements: personal inhalable sampling versus stationary sampling. Annals of Agricultural & Environmental Medicine. 2004; 11(2):269-77. Cited in PubMed; PMID 15627336.
Summary: Exposure to fungi was measured by Button Samplers during: 1) feeding on a hog farm, 2) cleaning and animal handling on a dairy farm, or 3) soybean uploading or handling on a grain farm. The greatest exposure to fungi occurred during soybean uploading and handling although all three groups were exposed to fungus during all three activities. The study demonstrated the usefulness of Button Samplers as a way to measure fungal contamination and exposure.

Relevance: Although the intention of this study was to determine whether a particular technique was reliable in measuring fungal exposure, it suggests that further study is necessary to determine the concentration and type of fungal exposure common to different types of farming. Knowledge of the varied exposures may assist human health practitioners in identifying specific tests and choosing appropriate treatments.

Ahonen E. Venalainen JM. Kononen U. Klen T. The physical strain of dairy farming. Ergonomics. 1990 Dec; 33(12):1549-55. Cited in PubMed; PMID 2286200.
Summary: The aerobic capacity (VO2 max) of 8 male and 15 female farmers was measured to determine physical strain of dairy farmer. For the females, VO2 max was greatest during feed and manure handling, but overall the farmers had aerobic capacities that were below average and that peaked only at 50% of total VO2 max. Males had moderate VO2 maxes but most activity also required less than 50% of VO2 max. However, women had a higher mean heart rate then men even though women subjectively found the work load less stressful than the men. The authors conclude that since women have overall lower VO2 max than men, even though the women in this study had lower VO2 max then the men studied, in conjunction with the higher heart rate of the women during activity, suggests that women's activities should be limited in the laborious process of dairy farming.

Relevance: This study demonstrates that dairy farming, and in particular feed and manure handling, does constitute aerobic activity. Although I would be hesitant to recommend reduced involvement by women without further studies demonstrating actual risk, it is important for human health practitioners to recognize that dairy farmers must be physically fit to engage in moderate aerobic activity in order to safely perform their job.

Anonymous. A 25-year-old farmer developed disorientation and collapsed after entering a manure pit on his dairy farm. Attempts at resuscitation were unsuccessful. What are the risks associated with this exposure and how can they be prevented?. Journal of Occupational & Environmental Medicine. 1995 Jun; 37(6):656-60. Cited in PubMed; PMID 7670908.
Summary: This is a letter to the editor asking about the risks, and prevention techniques, for asphyxiation in manure pits. Manure pits fit into the National Institute for Occupational Health and Safety's definition of an enclosed space but there are no Occupational Safety and Health Association guidelines for manure pits because most U.S. farms have fewer than 10 employees. There are also atmospheric hazards in addition to the engulfment, entrapment, and mechanical hazards. As the bacteria in the pit decays it gives of ammonia, hydrogen sulfide, carbon dioxide, and methane gases. Risks come from the gasses themselves or the Oxygen deficient environment. The toxic chemicals also pose a risk of explosion if there were an ignition.

Relevance: Manure pits pose a number of occupational threats to farmers in the form of atmospheric (asphyxiation), explosion, engulfment, entrapment, and mechanical hazards. When considering the human health threats to farmers on New England dairy farms we must consider whether those risks are similar or different between organic and conventional farmers.

Antognoli, MC, Lombard, JE, Wagner, BA, McCluskey, BJ, Van Kessel, JS, Karns, JS. Risk Factors Associated with the Presence of Viable Listeria monocytogenes in Bulk Tank Milk from US Dairies. Zoonoses and Public Health. 2008. Cited in PubMed; PMID: 18705657.
Ahead of Print- hopefully available soon! Abstract looks promising.

Beck, JP, Heultelbeck, A, Dunkelberg, H. Volatile organic compounds in dwelling houses and stables of dairy and cattle farms in northern Germany. Science of the Total Environment. 2007 Jan; 372(2-3): 440-454. Cited in Pubmed; PMID: 17118427.
Summary: This study measured the concentration of volatile organic compounds in autumn and spring on dairy farms-- outside, stable, and home levels. Farmers on these German farms reported symptoms of asthma, rhinitis, and conjunctivitis at work and occasionally at home. The study found no significant difference of concentrations between seasons. The measuring unit of VOC was TVOC (mean total VOC). TVOC was higher in dairy homes than regular houses probably because fuels and chemicals from the farm were carried inside the homes on shoes and clothing or perhaps some of the same chemicals were used in the homes due to availability. The highly prevalent compounds in the houses were aliphlatic and alicyclic hydrocarbons, aromatic compounds, and terpenes; stables had high levels of ketones, alcohols, and esters. The terpene concentration was low in the stable probably due to the fact hay instead of sawdust covered the floors. Overall, compared to scientific studies measuring VOCs and health effects, the levels found in the homes and stables of these dairy farms were likely too low to cause respiratory disease. However, paired with the high levels of fungal spores and bacteria as well as dust mites on the farm, VOCs may exacerbate respiratory symptoms.

Relevance: This article suggests that high levels of VOCs exist in farm houses and stables. VOCs most likely do not cause respiratory diseases, but may exacerbate existing respiratory symptoms, working in tangent with fungal spores, bacteria, and dust mites.

Bigras-Poulin M, Ravel A, Belanger D, Michel P. Development of agroenvironmental indicators to evaluate the hygienic pressure of livestock production on human health. International Journal of Hygiene & Environmental Health. 2004 July; 207(3):279-95. Cited in PubMed; PMID 15330396.
Summary: Zoonotic enteric diseases are often transmitted by food, water, and occasionally directly from animal to human. Many recent large scale outbreaks of such pathogens have been linked to contaminated drinking water and often traced back to food animal productions. Because it is nearly impossible to fully monitor all systems for potential outbreaks or plan via dynamic models, the authors sought to identify agroenvironmental indicators to measure or diagnose environmental situations. Agroenvironmental indicators have been used in the past to manage chemical pollution but use for microbiological hazards is a novel idea. Although imperfect, such indicators would use the best scientific knowledge while seeking simplicity and acknowledging the lack of available of data.

Relevance: It is well acknowledged that a better system is needed to identify potential human health risks as early as possible. The current model of inaction until the first cases are observed by physicians and an outbreak is recognized by public health officials is cumbersome and relies on human illness, and occasional death, to draw attention. Any system that identifies threats prior to infection in people has the potential to greatly alleviate suffering, morbidity, and epidemics.

Borucki, MK, Reynolds, J, Gay, CC, McElwain, KL, Kim, SH, Knowles, DP, Hu, J. Dairy farm reservoir of Listeria monocytogenes Sporadic and Epidemic Strains. Journal of Food Protection. 2004 Nov; 67(11):2496-2499. Cited in PubMed; PMID 15553633.

Carruth, A, Robert, A, Hurley, A, Currie, P. The impact of Hearing Impairment, Perceptions and Attitudes about Hearing Loss, and Noise Exposure Risk Patterns on Hearing Handicap among Farm Family Members. 2007 Jun; 55(6):227-234. Cited in PubMed; PMID 17601063.
Summary: This correlational study found that 80.4% of farmers suffered from hearing impairment. The study examined a convenience sample of 56 farmers recruited from agricultural events, one being "Dairy Day." Less than 10 farmers regularly wore hearing protective devices at work. High-frequency hearing loss in left ear, the belief that hearing protective devices prevents effective communication at work, and the self-reported assessment of hearing significantly predicted a hearing handicap.

Relevance: The article emphasized the irony of the situation. By worrying about daily communication and choosing not to don protective devices, long-term hearing and communication is severely compromised.

Fossler, CP, Wells, SJ, Kaneene, JB, Ruegg, PL, Warnick, LD, Eberly, LE, Godden, SM, Halbert, LW, Campbell, AM, Bolin, CA, Geiger Zwald, AM. Cattle and environmental sample-level factors associated with the presence of Salmonella in a multi-state study of conventional and organic dairy farms. Preventive Veterinary Medicine. 2005 Jan;67(1):39-53.
Summary: This study examined the prevalence of Salmonella in cattle and environmental samples of organic and conventional farms. Sick cows and cows within 14 days of calving or culling were most likely to shed Salmonella. Environmental samples of Salmonella were significantly higher than bulk tank milk samples. Sick pens, manure storage areas, maternity pens, hair coats of cows to be culled, milk filters, cow waterers and bird droppings in cow housings in descending order were significantly more likely to be Salmonella-positive than bulk tank milk. Organic and conventional farms did not differ in Salmonella prevalence. Midwestern farms, larger farms (over 100 cows), and non-winter seasons predicted higher Salmonella rates.

Relevance: This article is important because it indicates many environmental areas of the farm that are commonly Salmonella-positive. The article suggests that farms could monitor pathogen levels by testing some of these areas because the low prevalence in bulk tank milk might be undetectable and not an effective indicator. The article highlights the importance of recognizing the regions of the dairy farm with a higher Salmonella prevalence, so that they are regularly cleaned and monitored.

Cho S. Diez-Gonzalez F. Fossler CP. Wells SJ. Hedberg CW. Kaneene JB. Ruegg PL. Warnick LD. Bender JB. Prevalence of shiga toxin-encoding bacteria and shiga toxin-producing Escherichia coli isolates from dairy farms and county fairs. Veterinary Microbiology. 2006 Dec; 118(3-4):289-98. Cited in PubMed; PMID 16959442.
Summary: Shiga toxin-encoding bacteria (STB) and shiga toxin-producing Escherichia coli(STEC) were detected and isolated from dairy cattle and manure at farms and county fairs from 2001-2002. On dairy farms, 2.3% of 1750 fecal samples on conventional farms were STB-positive and 65% of conventional farms had at least one positive animal compared to 6.6% of 458 fecal samples from organic farms and 87.5% of organic farms had at least one positive animal. The difference between organic and conventional farms was not significant and the authors suggest that a conclusive statement about differences of STB prevalence cannot be made because the labels "organic" and "conventional" do not account for the differences in farming techniques that frequently occur within each group. STB was detected in 17.4% of 178 samples at county fairs and in 58.3% of manure piles. Twenty-six serotypes of STEC were identified from 43 isolates.

Relevance: Human health may be at risk with large percentages of STB identified in cattle, and particularly in manure piles that may enter the environment and be consumed by people. Furthermore, the majority of manure piles at county fairs were STB positive and over seventeen percent of cattle at county fairs were STB positive. This could result in serious human health risks from STB infection. The study also looked at differences between organic and conventional farms and although no significant difference was found, the authors remind us that human health risks may not be easily connected to farms based upon the category they fall under, since many other aspects of farming may confound any findings.

Choma D. Westeel V. Dubiez A. Gora D. Meyer V. Pernet D. Polio JC. Madroszyk A. Gibey R. Laplante JJ. Depierre A. Dalphin JC. Respective influence of occupational and personal factors on respiratory function in dairy farmers. Revue des Maladies Respiratoires. 1998 Dec; 15(6):765-72. Cited in PubMed; PMID 9923031.
Summary: Respiratory function of 245 French farmers was measured using questionnaires, spirometry, and allergological tests. Respiratory function was found to be significantly impaired on farmers working on traditional farms and respiratory function increased as the degree of modernity increased (notably through use of artificial hay drying systems and improved ventilation). Interestingly, no significant relationship between respiratory function and quantitative indicators of exposure or Ig-E mediated allergy was observed.

Relevance: This study demonstrates that dairy farming, and in particular, traditional dairy farming, puts farmers at risk for decreased respiratory function. Public health campaigns could center of modernizing dairy farms, particularly through increasing ventilation or improved hay drying systems, as a way to improve dairy farmer health. As there appears to be a dose-response (as modernization increases, respiratory function proportionally increases) it should be recognized that every small change can make a small improvement to the health of a farmer and should therefore be recognized as meaningful.

Dalphin JC, Bildstein F, Pernet D, Dubiez A, Depierre A. Prevalence of chronic bronchitis and respiratory function in a group of dairy farmers in the French Doubs province. Chest. 1989 June; 95(6): 1244-7. Cited in PubMed; PMID 2721258.
Summary: The authors used a questionnaire, medical history, and spirometric studies to compare 250 dairy farmers with 250 control subjects in a province in France. Chronic bronchitis was found to be significantly more frequent in dairy farmers than in the control group. It also appears that increased age (subjects over 40) and non-smoking further correlate with the prevalence of chronic bronchitis and bronchial obstruction, however the sample size was not large enough to prove statistical significance. The age relationship was hypothesized to be a result of duration of exposure, as most dairy farmers in the region began work before age 10.

Relevance: Although there are several studies linking grain farming with higher prevalence of Chronic Obstructive Pulmonary Diseases (COPD's) such as chronic bronchitis, this study suggests that dairy farmers may encounter similar risk. Diseases such as COPD can be severely debilitating and result in shorter duration of life as well as poorer quality of life which makes this a serious issue of concern. The authors did not mention whether the farms were organic, conventional, or a mixture of both and it would be interesting to discern whether risk changes between the two farming methods.

Esiobu N. Armenta L. Ike J. Antibiotic resistance in soil and water environments. International Journal of Environmental Health Research. 2002 Jun; 12(2):133-44. Cited in PubMed; PMID 12396530.
Summary: Low levels of antibiotic resistance was widespread for ampicillin, penicillin, vancomycin, tetracycline, and streptomycin in 7 different soil and water sampling areas. Dairy farm manure contained significantly more resistant bacteria than other sites with tetracycline resistance the most prevalent of total bacteria. Resistance trends correlated to the abundance and type of bacteria present.

Relevance: Antibiotic resistance in soil and water may present a serious public health threat including opportunistic pathogens. Public health and human health practitioners must work with environmental, farming, and animal health groups to reduce the threat of antibiotic resistance in the environment and with all animals (human and others).

Franklin, RC, Depczynski, J, Challinor, K, Williams, W, Fragar, LJ. Factors affecting farm noise during common agricultural activities. Journal of Agricultural Safety and Health. 2006 May; 12(2):117-125. Cited in PubMed: PMID: 16724788.

Gates, G, Jones, S. A Pilot Study to Prevent Hearing Loss in Farmers. 2007 Nov-Dec; 24(6):547-553. Cited in PubMed: PMID 17973732.
Summary: This comparison study examined the frequency of hearing protection use and hearing loss attitudes of intervention and control farmers. After the research team conducted noise assessments and educational sessions, placed protection devices in accessible areas of the workplace, and sent reminder brochures, intervention farmers significantly increased the frequency of wearing hearing protection devices one and two months after the intervention. Increasing awareness of susceptibility by emphasizing the effect of hearing loss on family relationships and future business as well as sharing the results of the noise assessments may have been effective components of the intervention. Farmers also indicated that they did not use protective devices before because they were lazy or it was not a habit. Accessibility as well could also have been an effective component of the intervention. Also noted in the study, was the idea that the partnership between the researchers and the farmers contributed to the increased usage.

Relevance: This article adds a useful dimension to the research question as it illustrates how one research team was able to effectively change the behavior of a group of farmers through education, noise assessments, reminder brochures, and accessible protective devices. Despite the complex barriers to hearing device usage, behavioral change is possible. This article offers an intervention aspect to the research question.

Gainet, M, Thaon, I, Westeel, V, Chaudemanche, H, Venier, AG, Dubiez, A, Laplante, JJ, Dalphin, JC. Twelve-year longitudinal study of respiratory status in dairy farmers. The European respiratory journal. 2007 Jul; 30(1): 97-103. Cited in PubMed; PMID 17392318.

Gerasimon G. Bennett S. Musser J. Rinard J. Acute hydrogen sulfide poisoning in a dairy farmer. Clinical Toxicology: The Official Journal of the American Academy of Clinical Toxicology & European Association of Poisons Centres & Clinical Toxicologists. 2007 May; 45(4):420-3. Cited in PubMed; PMID 17486486.
Summary: Hydrogen sulfide gas is produced in occupational settings from decaying organic matter. H2S is a mitochondrial toxin that inhibits cytochorme-aa3preventing cellular aerobic metabolism. This paper explores the case of a subject who collapsed seconds after entering a poorly ventilated tank of degrading eggs and required several months of neuro-rehabilitation to regain basic life functions.

Relevance: Hydrogen sulfide gas occurs with the decay of sulfur-containing proteins and is a byproduct of animal and human waste. The effects are concentration dependent with a steep dose-response curve. Duration of exposure is of lesser concern. At low levels olfactory perception of H2S gas is possible however as concentration increase above 100 ppm, the gas causes immediate olfactory paralysis. This is of concern given that concentrations of 250 ppm lead to bronchospasm, acute lung injury, nausea and vomiting and at 500 ppm symptoms become systemic. Above 750 ppm exposed patients may become apneic, have asphyxial seizures, or even instantaneous death with just one breath. It is therefore apparent that hydrogen sulfide exposure should be prevented in any farming environment.

Groenendaal, H, Zaqmutt, FJ. Scenario analysis of changes in consumption of dairy products caused by a hypothetical causal link between Mycobacterium avium subspecies paratuberculosis and Crohn's disease. Journal of Dairy Science. 2008 Aug; 91(8):3245-3258.

Grusenmeyer DC, Cramer TN. Manure management. A systems approach. Journal of Dairy Science. 1997 October; 80(10):2651-4. Cited in PubMed; PMID 9361237.
Summary: This article proposes more cross-discipline coordination of manure, and particularly, nutrient management. Manure management is changing, and with it society is becoming less tolerant of potentially negative impacts. Producers are being forced to consider environmental protection costs while continuing to improve the efficiency of their farms. The public is becoming concerned about links between disease outbreaks and proximity to farming, in particular it is known that manure nitrate is linked to Escherichia coli. Linkages like these raise concerns for human health. Excessive nitrogen application of fields may be an environmental threat resulting in concerning levels of nitrates in drinking water. Odors and flies are also increasingly becoming concerns. Although odors may be seen more as a nuisance and potentially as adversely affecting quality of life, their presence may serve as indicators for other concerns that may directly affect human health. Flies are more than a nuisance, and their presence around manure and other potentially pathogenic farm waste could make them potential vectors for disease transmission. Although the authors drawn no firm conclusions about how to alleviate the threats that they identify, their recognition that manure management must become more interdisciplinary is a critical first step.

Relevance: Improper and unnecessary use of manure appears to be linked to many human health threats. As large scale farms continue to produce unnecessary levels of nitrates and nitrites, and dispose of such waste inappropriately, human health may be affected via contaminated drinking water and air born vectors. Physicians and public health officials should join the interdisciplinary approach to manure management to ensure that the human health perspective is properly recognized and addressed.

Hallman EM. Gelberg KH. Hallisey JL. The NIOSH Fatality Assessment and Control Evaluation (FACE) program: a New York case study illustrating the impact of a farm manure pump PTO entanglement. Journal of Agromedicine. 2005; 10(3):57-64. Cited in PubMed; PMID 16537317.
Summary: This case study examines the fatality of a New York state farmer who's shirt became wrapped around the power take-off (PTO) shaft of the manure pump while transferring manure from an underground storage pit to a lagoon. The farmer subsequently became wrapped around the PTO. Upon examining the case the FACE program made the subsequent recommendations: 1) PTO powered equipment should not be operated unless the PTO shield is in place and in good condition, 2) power to equipment should be turned off prior to making mechanical adjustments, 3. manure handling systems should be designed to facilitate operator safety, 4) farm workers should be healthy and well rested prior to performing hazardous activities, and 5) dairy farm workers should be trained in manure handling safety and knowledgeable about manure hazards.

Relevance: As with many labor intensive occupations, manure handling poses a number of intrinsic risks. Human health practitioners should be knowledgeable about these risks and should engage in preventative education to mitigate them.

Harvey, RB, Droleskey, RE, Sheffield, CL, Edrington, TS, Callaway, TR, Anderson, RC, Drinnon, DL, Ziprin, RL, Scott, HM, Nisbet, DJ. Campylobacter Prevalence in Lactating Dairy Cows in the United States. Journal of Food Protection. 2004 July;67(7):1476-1479. Accession number 13965095.

Hass-Slavin, L, McColl, MA, Pickett, W. Challenges and Strategies Related to Hearing Loss among Dairy Farmers. Journal of Rural Health. 2005 Fall; 21(4):329-36. Cited in PubMed; PMID 16294656.
Summary: Hearing loss is a problem on dairy farms due to old tractors, grain dryers, and vacuum pumps. Communication with coworkers, family members, farmers at meetings, and people involved in the dairy industry is negatively affected by hearing loss. Farmers often choose to forego hearing protection devices in order to hear others at work and detect malfunctioning machinery or sick cows, which leads to the hearing loss. Farmers use many practical and emotional coping strategies. They try to control the conversation topic, maintain good relationships despite hearing difficulties, move closer to the speaker or ask for repetition, start using hearing protection devices, and may use hearing aids at home. Emotionally, farmers may cope by avoiding embarrassing, stressful situations like farmers' meetings. They may minimize the disability by pretending to understand the conversation or guessing. They also may cope by recovering after a stressful day of noisy work by creating a quiet house environment free from television and other noise. Hearing loss for dairy farmers is a prevalent, but invisible issue due to stigma. Most importantly, a conflict exists between needing to hear machinery, coworkers, and animals to prevent costly mistakes and worrying about hearing loss.

Relevance: This article provides a wonderful introduction to hearing loss and dairy farming. The authors interview 13 dairy farmers in Canada with hearing loss, so it will be important to determine if dairy farmers in the United States use the same equipment and share similar ideas and experiences. This article provides a qualitative account of the issue. The article contributes to the research question by illustrating challenges and coping strategies for dairy farmers with hearing loss.

Hoe, FG, Ruegg, PL. Opinions and practices of Wisconsin dairy producers about biosecurity and animal well-being. Journal of Dairy Science. 2006 Jun; 89(6):2297-2308. Cited in Pubmed; PMID 16702297.
Summary: This study examines the beliefs and practices of Wisconsin dairy farmers, which generally differed based upon farm size. Almost half of the farmers purchased cattle, but few tested them. They were more likely to be tested as the herd size increased. Almost all of the farmers agreed that bedding is important for mastitis control, but 44% reported it was only changed a few times a week. Medium and large farms changed the bedding less frequently. Teat contamination and bedding levels were associated. Large farms were more likely to have a separate milking area for mastitic cows or would disinfect the equipment after use; smaller farms more likely used a different milking unit on sick cows or would milk them last. Larger farms were more likely to undergo bulk tank testing probably because they had greater access to these services. Although many farmers recognized that Johne's disease was an important issue, few participated in the state's control program. Smaller farms culled the cows immediately, whereas larger farms culled if they showed further problems. Most farms would stop feeding pooled milk to calves. Many farms housed sick and healthy milking farms together; larger farms were able to separate the groups more easily. Almost all veterinarians washed boots every time they visited the farm, but nutritionists and other visitors were less likely to wash their boots. Only 57% of animal handlers on the farm washed their boots. Very few people changed their clothing before each visit or after handling sick animals. Zoonotic knowledge increased as farm size increased.

Relevance: This article is significant because it captures the discrepancies between beliefs and practices of dairy farmers and the constraints of small and large farms. Information on bedding practices, separation of sick and healthy cows, preventive milking practices for mastitic cows, the lack of enrollment in John's control program, and the boot and clothing discussion contribute to an understanding of how farms are limited by their size in their pathogen prevention approach and how farmers still need to be educated about some preventive measures and pathogens.

Hoppin, JA, Umbach, DM, Kullman, GJ, Henneberger, PK, London, SJ, Alavanja, MC, Sandler, DP. Pesticides and other agricultural factors associated with self-reported farmer's lung among farm residents in the Agricultural Health Study. Occupational and environmental medicine. 2007 May; 64(5): 334-341. Cited in Pubmed; PMID 17182642.

Horrigan L, Lawrence RS, Walker P. How sustainable agriculture can address the environmental and human health harms of industrial agriculture. Environmental Health Perspectives. 2002 May; 110(5):445-56. Cited in PubMed; PMID 12003747.
Summary: This is an excellent overview article on sustainability and the threats posed by conventional agriculture to the environment, diet, and public health. The authors' site over 100 references arguing that environmental and human health problems associated with conventional food production practice externalize farmers' cost savings to society as a whole. Much of the argument centers on the threats of conventional animal agriculture although it is not always clear when the threats from cattle farming are specific to dairy versus non-dairy farms.

Relevance: Relevant human health risks included in the article include threats from pesticide residues, pollution from factory farms, inadvertent production of new strains of foodborne pathogens, and genetically engineered foods. Any of these threats may result in serious effects on the morbidity and mortality rates of the farmers as well as the community, depending on their association with dairy farming.

Jackson-Smith, D, Gillespie, GW. Impacts of farm structural change on farmers' social ties. Society & Natural Resources. 2005 Mar; 18(3):215-240.
Summary: The social ties of farmers on small, transitional, and large-scale dairy farms were compared using sample communities from the industrial south and traditional Northeast. The social tie indicators examined two categories of social interaction: relationships with neighbors (how well do you know neighbors, complaint level) and participation in civic/community organizations. The findings were quite complex. The results were ultimately determined by demographics as opposed to farm size. The only indicator consistently predicted by farm size was the neighbors' complaint level of flies, sanitation, etc. Regardless of farm size, relationships with neighbors and community participation were largely based upon the characteristics of the farmers themselves. Older farmers, farmers with children, and farmers on multi-generational family farms tended to report knowing their neighbors well. Education, age, children at home, and hired help increased the likelihood of social integration and community engagement.

Relevance: This article contributes a social health dimension to our human health research. Social health is very strongly linked to mental health (resilience, coping, well-being), so social integration is an important health concern. It would be interesting to research the demographics of organic farmers and whether collectively, organic farmers demonstrate greater social participation and quality of social ties.

Jayarao, BM, Donaldson, SC, Straley, BA, Sawant, AA, Hedge, NV, Brown, JL. A survey of foodborne pathogens in bulk tank milk and raw milk consumption among farm families in pennsylvania. Journal of Dairy Science. 2006 July; 89(7):2451-2458. Cited in PubMed; PMID: 16772561.
Summary: This study surveyed 248 dairy farmers in Pennsylvania and found that 42.3% of the farmers consumed raw milk and 68.5% of these drinkers were well-aware of the risk of food-borne pathogens. Farmers cited taste and convenience as the primary reasons they drink raw milk from the bulk tank. Dairy farmers who were not aware of the pathogen risks were two times more likely to drink raw milk. Dairy producers who lived on the farm were three times more likely to drink raw milk. The study also tested the presence of these pathogens in the bulk tank milk of all farmers. They found 13% of the samples contained at least one pathogen. Pathogens present included Campylobacter jejuni, Shiga toxin-producing E. coli, Listeria monocytogenes, Salmonella, and Yersinia enterocolitica. Interventions are necessary to educate and reinforce the message that raw milk contains foodborne pathogens.

Relevance: This study is interesting because it parallels the hearing loss research. Farmers knowingly engage in risky behavior for immediate benefits and disregard long-term consequences. Here, convenience and taste inspire farmers to drink raw milk, whereas desire to hear coworkers, malfunctioning machinery, and sick animals lead farmers to work sans protective hearing devices. A subset of farmers do not realize the real threat of pathogens and hearing loss and the rest value the immediate benefits, so it is very important that farmers are further educated on the significant risks of their actions.

Klein W. Chemical-physical risks originating from dead animals or animal products for the health of humans and animals and for the environment. DTW - Deutsche Tierarztliche Wochenschrift. 1997 Jul; 104(7):254-6. Cited in PubMed; PMID 9312474.
Summary: On farm burial of livestock may pose local threats to groundwater via release of nitrogen and other organic compounds. Although rendering reduces many of these risks, it is unknown how antibiotics respond to rendering and whether there could be risks to human health from rendering animals with antibiotics still present in their corpses.

Relevance: The degree of livestock burial in New England is not currently known by the members of this course, although it is presumed that most farms rely on rendering of deceased bodies. Should there be a difference in reliance on burial versus rendering between organic and conventional farms, this could affect the indirect risks to human health by one or another method. The authors also raise the important point about lack of knowledge of the effects of rendering on antibiotics which should be further explored to ensure that antibiotic residues are not entering the air or soil via rendering plants, or in no way affecting the exposure of rendering employees.

Koskela, HO, Happonen, KK, Remes, ST, Pekkanen, J. Effect of farming environment on sensitisation to allergens continues after childhood. Occupational & Environmental Medicine. 2005; 62(9):607-611. DOI 10.1136/oem.2004.014852.
Summary: Previous studies indicate that children living on a farm are less sensitive to allergens than non-farm children. This study explored the question at the adult level by comparing women residing on a dairy farm with non-farm women. This study demonstrated that farm women are less susceptible to common allergens like pollen and cats. The researchers hypothesized that the mechanism that reduces sensitivity to allergens continues to operate throughout the years as the women who lived both as children and adults on farms were less sensitive than women who lived on a farm only as children or adults. The reduction of allergen sensitivity was also dose-dependent to time spent near the cattle. Women with reduced allergen sensitivity to common allergens were highly sensitive to bovine dander.

Relevance: This study suggests that human health on a dairy farm is affected by bovine dander. Bovine dander allergies increase over time. (However, human health is positively affected on a dairy farm by a reduction of common allergies like pollen and cats).

Kronqvist M. Johansson E. Pershagen G. Johansson SG. van Hage-Hamsten M. Increasing prevalence of asthma over 12 years among dairy farmers on Gotland, Sweden: storage mites remain dominant allergens. Clinical & Experimental Allergy. 1999 Jan; 29(1):35-41. Cited in PubMed; PMID 10051700.
Summary: In 1996 over eighty-six percent of dairy farmers from the Gotland region of Sweden returned questionnaires concerning airway symptoms (n=1577) and from these, 461 received a medical exam, skin-prick test, and blood sampling for identification of allergies and asthma. The frequency of allergic hypersensitivity was similar between the 1996 group and a sample taken in 1984 (41.7% versus 40.0%) however the prevalence of asthma increased significantly (5.3% to 9.8%) as had asthma in conjunction with rhinoconjunctivitis (3.7% vs 7.0%). Interesting, rates of rhinoconjunctivitis alone did not change (36.5% vs 33.1%). Storage mite allergy in 1996 was 6.5% and constituted an important cause of allergic symptoms. The increase in the prevalence of asthma and rhinoconjuctivitis in conjunction with asthma suggest that farmers in the Gotland region are exhibiting more lower respiratory problems than in the past which may indicate a change in environmental exposures.

Relevance: Increased prevalence of asthma and asthma plus rhinoconjunctivitis in this community suggests a shift from irritants that resulted in upper respiratory infections to the lower respiratory system. Such a change may indicate a worrisome change in environmental conditions, as asthma and other lower respiratory disease may result in lost productivity for the farmer as well as decreased quality of life and potentially decreased life-expectancy in extreme conditions.

Lyautey E, Lapen DR, Wilkes G, McCleary K, Pagotto F, Tyler K, Hartmann A, Piveteau P, Rieu A, Robertson WJ, Medeiros DT, Edge TA, Gannon V, Topp E. Distribution and characteristics of Listeria monocytogenes isolates from surface waters of the South Nation River watershed, Ontario, Canada. Applied & Environmental Microbiology. 2007 Sep; 73(17):5401-10. Cited in PubMed; PMID 17630309.
Summary: Listeria monocytogenes is a pathogen believed to be widely distributed in the environment but also potentially more prevalent near farm land. Listeria spp. are carried in asymptomatic livestock and excreted in fecal matter. In particular, ruminants can shed significant numbers of L. monocytogenes increasing their density in surrounding soil and drainage water. This study explored the distribution of L. monocytogenes isolates in a watershed dominated by human development, farming, and wildlife habitats. Significantly higher numbers of L. monocytogenes were found closer to upstream dairy farms, and the majority discovered in the study region was of bovine origin. Furthermore, several of the pulsotypes of L. monocytogenes found in the surface waters were multi-antibiotic resistant. In addition to concerns about indirect transmission of Listeria spp. to people, the presence of Listeria could serve as an indication of potential fecal contamination originating from beef and dairy operations in the future.Relevance: Listeria monocytogenes is responsible for severe food-borne infections in humans and causes 20-50% mortality in susceptible populations. Its association with dairy farms, and transmissibility via surface waters, make it a pathogen of great concern for human health practitioners. Recognition that L. monocytogenes contamination is higher closer to dairy farms should help physicians identify the source of potential outbreaks in farmers and the surrounding community. Studies such as these, that identify the source and spread of high mortality pathogens, are critical to improving human health.

Mastrangelo, G, Grange, JM, Fadda, E, Fedeli, U, Buja, A, Lange, JH. Lung cancer risk: effect of dairy farming and the consequence of removing that occupational exposure. American Journal of Epidemiology; 161(11):1037-1046. Cited in PubMed; PMID 15901624.

McLay CD. Dragten R. Sparling G. Selvarajah N. Predicting groundwater nitrate concentrations in a region of mixed agricultural land use: a comparison of three approaches. Environmental Pollution. 2002; 115(2):191-204. Cited in PubMed; PMID 11706792.
Summary: Eighty-eight sites within the intensive agricultural region of the Waikato Region of New Zealand were sampled biannually for three years for nitrate levels. The Resource Management Act in New Zealand requires the natural environment to be managed sustainably. Nine percent had groundwater nitrate concentrations above the World Health Organization's maximum allowable concentration for potable drinking water and over half of the sites had concentrations that indicated human activities. Some of the study's findings suggested that nitrate concentrations in groundwater increased with the proportion of dairy farms in the proximity. In addition, there was also evidence that hydrogeology may be one of the greatest factors in determining whether shallow groundwater is at risk for nitrate contamination.

Relevance: Nitrate pollution can result in contamination of drinking water which can result in nitrate poisoning in humans. Infants under five months of age are particularly at risk for methemoglobinemia with approximately a 10% fatality rate. Assuming that New Zealand's requirement for sustainable management of the natural environment parallels of the goals of organic dairy farming in New England, the findings from this study may provide insight to our situation and therefore shed light on the risk of nitrate exposure to humans near New England dairy farms.

Miller WA. Lewis DJ. Lennox M. Pereira MG. Tate KW. Conrad PA. Atwill ER. Climate and on-farm risk factors associated with Giardia duodenalis cysts in storm runoff from California coastal dairies. Applied & Environmental Microbiology. 2007 Nov; 73(21):6972-9. Cited in PubMed; PMID 17873066.
Summary: This study of five coastal California farms over two storm seasons detected Giardia duodenaliscysts in 41% of runoff samples near cattle less than 2 months old and in 10% of samples near cattle over 6 months old. Instantaneous loads of cysts also showed a seasonal effect. Vegetative buffer strips were found to significantly reduce waterborne cysts in storm runoff and a dose-effect was found where the greater the number of buffer strips utilized the greater reduction of concentration of G. dudodenaliscysts. Straw mulch, scraping manure, seed application, and cattle exclusion did not significantly affect the concentration or load of Giardia cysts.

Relevance: Communities downstream from dairy farms are at risk of contamination and infection from Zoonotic agents such as Giardia duodenalis. Studies such as this, with identification of risks (higher for young calves) and development of solutions (vegetative buffers) adds to the tools that interdisciplinary groups can use to prevent exposure of G. duodenalis and other pathogens in people.

Molkentin J. Giesemann A. Differentiation of organically and conventionally produced milk by stable isotope and fatty acid analysis. Analytical & Bioanalytical Chemistry. 2007 May; 388(1):297-305. Cited in PubMed; PMID 17393158.
Summary: Increasing organic milk sales necessitates a means to identify if milk labeled "organic" truly comes from organic sources. This pilot study evaluated organic and conventional milk from Germany to identify differences in composition. Fatty acid analysis enabled complete distinction of the different types of milk, likely because of the different diets. Other indicators included differences in stable carbon isotopes but there was no difference in Nitrogen or Sulfur isotopes between the two groups.

Relevance: Should there be health benefits to consuming organic, versus conventional, milk people will want to ensure that the milk they purchase and likely pay more for is labeled correctly. This study begins to pursue methods of quality assuance. Interestingly, the authors did not evaluate milk for antibiotic, growth hormone, difference in pathogen levels, or other residues that may be more important to some consumers than the milk composition itself. Regardless, some measure of quality assurance will at least ensure some protection of the consumer, and potentially of their health.

Nonnenmann, M, Anton, D, Gerr, F, Merlino, L, Donham, K. Musculoskeletal Symptoms of the Neck and Upper Extremities among Iowa Dairy Farmers. American Journal of Industrial Medicine. 2008; 51(6):443-451. DOI 10.1002/ajim.20582.
Summary: This study examined the musculoskeletal symptoms (MSS) of dairy farmers in Iowa. Three-quarters of the participants experienced at least one MSS. Shoulder MSS affected 54% of the participants. Neck MSS (43%) was significantly associated with tractors and manual feeding. Wrist/hand MSS (40%) was associated with manually cleaning animal stalls. The farmers reported little disability, which was not surprising as disabled farmers would probably not be working.

Relevance: This 2008 study suggests that MSS is a very prevalent problem despite the modernization of the farm. Many tasks are still performed manually and the repetitive and/or strenuous motions stress the body.

Oliver, SP, Jayarao, BM, Almeida, RA. Foodborne pathogens in milk and the dairy farm environment: Food safety and public health implications. Foodborne Pathogens and Disease. 2005; 2(2):115-129. Cited in PubMed; no PMID. (Accession number 000238251700001).
Summary: This review article presented the isolation rates of various studies for a range of foodborne pathogens. Although these rates varied due to geography, season, technique, herd size, they clearly proved that foodborne pathogens commonly exist in bulk tank milk. This article provides a wonderful overview of foodborne pathogen transmission. Pathogens can be excreted in feces or milk and contaminate milk products. Many people choose to drink unpasteurized milk and risk pathogen exposure. Contamination also can occur at the pasteurization level due to biofilms, resilient pathogens, or faulty pasteurization.

Relevance: This article emphasizes the prevalence and great risk of foodborne pathogens in dairy products. This article serves as a foundation for foodborne pathogen research as it clearly outlines the various ways of spread, contamination, and pathogen transmission.

Ottoson, J, Nordin, A, von Rosen, D, Vinneras, B. Salmonella reduction in manure by the addition of urea and ammonia. Bioresource Technology. 2008;99(6):1610-1615. DOI 10.1016/j.biortech.2007.04.009.

Pinzke S. Changes in working conditions and health among dairy farmers in southern Sweden. A 14-year follow-up. Annals of Agricultural & Environmental Medicine. 2003; 10(2):185-95. Cited in PubMed; PMID 14677910.
Summary: The authors used a repeat mail in survey to compare 2002 working conditions and health among southern Swedish dairy farmers with results compiled in a similar 1988 survey. Between eighty and ninety percent of respondents (83% male, 90% female) reported symptoms of musculoskeletal system within the 12 months prior to the 2002 survey with significantly higher complaints of shoulder, neck, and wrist/hand symptoms. The average worker in the 2002 group increased the working time per week, number of cows milked, and usage of milking units. Loose-housing systems had also increased from nearly nonexistence in 1988 to 25% of usage by 2002, with tethering systems continuing to make up the other 75%. Although most milkers wished and needed to continue their work on the farm many were forced to retire 10-15 years earlier than wanted because of working conditions, i.e., health problems.

Relevance: Dairy farming carries a high occupational hazard. The nature of the work may require difficult, awkward, repetitive motions resulting in chronic injury and potentially disability. The findings of this study suggest that as farms move from tethered to loose-housing systems, and possibly as the amount of work increases to meet demand, the number and type of injury is likely to increase. This means that farmers may have a greater number of upper extremity and upper thoracic and cervical injuries rather than the knee, hip, and lumbar injuries that were more prevalent in the past. Indentifying changes in trends in studies such as this, and identifying the potential for injury and other risks before they occur, can help human health practitioners with prevention and treatment.

Prior, C, Falk, M, Frank, A. Longitudinal changes of sensitization to farming-related antigens among young farmers. Respiration. 2001; 68(1):46-50. Cited in PubMed; PMID: 11223730.

Roberts, AJ. Pathogen, host and environmental factors contributing to the pathogenesis of listeriosis. Cellular and molecular life sciences. 2003; 60(5):904-918. Cited in PubMed. PMID 12827280.

Samanidou, V, Nisyriou, S. Multi-residue methods for confirmatory determination of antibiotics in milk. Journal of Separation Science. 2008 Jun; 31(11):2068-2090. Cited in PubMed; PMID: 18615808.

Sato, K, Bennedsgaard, TW, Bartlett, PC, Erskine, RJ, Kaneene, J.B. Comparison of Antimicrobial Susceptibility of Staphylococcus aureus Isolated from Bulk Tank Milk in Organic and Conventional Dairy Herds in the Midwestern United States and Denmark. Journal of Food Protection. 2004 Jun; 67(6):1104-1110. Accession number 13722883.

Smith, JM, Parsons, RL, Van Dis, K, Matiru, GN. Love thy neighbor- But does that include a six hundred eighty-four cow dairy operation? A survey of community perceptions. Journal of Dairy Science. 2008 Apr; 91(4):1673-1685. No PMID. DOI 10.3168/jds.2007-0702.

Stack, SG, Jenkins, PL, Earle-Richardson, G, Ackerman, S, May, JJ. Spanish-speaking dairy workers in New York, Pennsylvania, and Vermont: results from a survey of farm owners. Journal of Agromedicine. 2006; 11(2):37-44. Cited in PubMed; PMID: 17135141.
Could add health disparities perspective to human health discussion.

Venier, AG, Chaudemanche, H, Monnet, E, Thaon, I, Fury, R, Laplante, JJ, Dalphin, JC. Influence of occupational factors on lung function in French dairy farmers. A 5-year longitudinal study. American Journal of Industrial Medicine. 2006; Apr 49(4): 231-237. Cited in PubMed; PMID 16550561.

Westeel, V, Julien, S, De Champs, C, Polio, JC, Mauny, F, Gibey, R, Laplante, JJ, Aiache, JM, Depierre, A, Dalphin, JC. Relationships of immunoglobulins E and G sensitization to respiratory function in dairy farmers. European Respiratory Journal. 2000; Nov 16(5): 886-892. Cited in PubMed; PMID 11153588. http://www.ag.auburn.edu/~schmisp/safety/dairy.htm