Groups have been referred to as "sensitive populations" because their response to particular exposures is presumed to be greater than that of the general population. Very young and very old individuals have traditionally been considered sensitive to various stresses (heat, cold, infectious agents). On the family farm, the youngest and the oldest members of the family are sometimes pressed into service in times of heavy work demands or just because they want to help out. This may put these populations at greater risk for injury or illness. The elder person with poor eyesight because of a cataract is more likely to have an accident while operating machinery. The youth who is inexperienced may take unnecessary risks or fail to utilize personal protective equipment. These sensitive populations require education and supervision to ensure safe participation in farming. Groups such as "Farm Safety 4 Just Kids" (www.fs4jk.org), 4-H Clubs, and Future Farmers of America help to provide this education.
In addition to sensitive populations that actually work on farms, additional sensitive populations are exposed to potential agricultural risks because of encroachment of housing and business development into areas that were previously farmland and immediately adjacent to land currently under cultivation or used as pasture. Drift of fertilizers, pesticides, herbicides, and odors only rarely have true adverse health effects, but involuntary exposures of any kind are emotionally and physically stressful and may lead to symptoms and legal conflicts. Persons with immunosuppression for organ transplant or due to infection have additional theoretical risk from living in close proximity to an agricultural operation.
More general concerns have been raised about the effect of genetically modified foods and organisms on the quality and safety of the food supply and risks for the development of "super-weeds" and highly resistant organisms. The issues are controversial and much additional data is needed for final answers, but a recent (2004) Food and Agriculture Organization (FAO) conference on genetically modified crops has shed some light on these concerns. More than 80% of genetically modified crops are herbicide resistant, meaning herbicides can be applied to the crop to control weeds without affecting the crop itself. This decreases the rate of soil erosion, preserves moisture in the soil, and decreases hand labor use, all positive impacts. While some weed resistance has developed, it appears that the rate of resistance development is not significantly different from that which occurs naturally. More study of the issue was recommended. Crops that include Bacillus thuringiensis (Bt) are resistant to many pests (the Bt incorporated in the plant material is toxic to the insect that ingests it). While pest species may develop resistance over time, decreasing rates of pesticide use on crops with Bt may decrease resistance pressure, making other pesticides that are used more effective. Again, the issues are complex and the FAO study group recommended further study. Drought and salinity tolerance are additional characteristics that may be engineered into plant species. While commercial crops with these characteristics are probably years away, basic research suggests that crops of this type may allow wider areas of the planet to be successfully cultivated (6).
Concerns about changes in soil ecosystems as a result of genetically modified (GM) crop cultivation were also discussed. Thus far, research on GM crops has shown very minor alterations in these characteristics compared to those produced by other sources of variation (temperature, moisture level, or organic matter level) in soil-borne ecosystems.
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