Exposures to pollutants and contaminants can occur through water or soil, which can be contaminated naturally or through human activities. The toxicity and adverse health effects of these substances depend on exposure route, quantity, and duration. Mechanisms of water contamination include runoff, flooding, infrastructure failures, and contamination from air and surface water pollution. Pesticides and organophosphates commonly are used in agricultural and residential applications, frequently cause water contamination, and commonly cause poisoning in agricultural workers and gardeners. Soil contamination disproportionately affects minority and low-income populations because they are more likely to live in proximity to a pollution source. Fetuses, children, and individuals with preexisting medical conditions are more vulnerable to adverse health effects of soil contamination compared with healthy adults. Some of the most common soil pollutants are heavy metals, pesticides, and polychlorinated biphenyls. Preventing exposure to contaminated soil involves avoidance of historically contaminated sites and ingestion of soil. Approaches to cleanup depend on the extent of contamination, location, and planned future use of the land. Remediation strategies include containment, bioremediation, chemical oxidation, soil washing, and thermal treatment.

Case 3. KF is a 50-year-old patient who is a farmer. He presents with watery eyes, chest tightness, and weakness. You ask when these symptoms started and he tells you in the spring. KF says he initially thought they were due to seasonal allergies; however, nasal steroids and antihistamines have not alleviated the symptoms. He says they usually worsen the day after he sprays his crops. A physical examination reveals that KF also has increased salivation, nausea, diarrhea, and blurry vision.