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.
Water Contamination
Ensuring water safety is one of the many important functions of public health.58 Water contamination can make water unsafe for human use and cause illness and disease. Clean water is essential for daily living and is needed for consumption, food preparation, and cleaning. Acknowledging the interconnectedness of water with soil and air is important in understanding the etiologies of conditions caused by water contamination and the connection of water to ecosystem, plant, animal, and human health.59
Although drinking water quality in public water systems is regulated in the United States, high concentrations of contaminants can reach unsafe levels through several mechanisms. Private wells are largely unregulated and it remains the responsibility of well owners to test the water for safety.58 The Environmental Protection Agency (EPA) recommends testing of private wells at least annually for bacteria, nitrates, and other contaminants.60
Water can become contaminated at its source, after being processed at a water treatment plant, or during distribution.58 Water sources include groundwater, lakes, and rivers. Water contaminants are chemicals and pathogens present in drinking water at sufficiently high concentrations to cause harm.
CHEMICAL CONTAMINANTS
Chemicals of concern in tap water include arsenic (natural deposits and industrial pollution), radon (forms naturally in groundwater with breakdown of uranium, radium, and thorium), lead (pipes), nitrate (fertilizers and food processing waste), and copper (pipes and industrial pollution).58 Hazardous chemicals (often pesticides and herbicides from farms, industrial plants, homes, and golf courses) can cause acute toxicity or death. Chronic toxicity can lead to later neurologic problems or development of cancer.61–64
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