More than 80,000 synthetic chemicals are currently in use in the United States. Despite this scale, the Safe Drinking Water Act, the primary federal law intended to regulate drinking water quality, establishes standards for only 91 contaminants. Numerous studies have shown that drinking water contains additional substances that are not addressed by existing regulations.
One group of chemicals increasingly detected in drinking water is poly- and perfluoroalkyl substances (PFASs). These compounds are used in fire retardants, oil- and water-repellent products, furniture, waterproof clothing, takeout food containers, and non-stick cookware. PFAS compounds are highly soluble and are not effectively removed by standard wastewater treatment processes. A study published in Environmental Science & Technology Letters (2016; 3(10):344–350) estimated that 16.5 million Americans have detectable levels of at least one PFAS compound in their drinking water. The senior author of the study, Elsie Sunderland of Harvard University, noted that these compounds exhibit immunotoxic effects in children and that existing drinking-water safety guidelines may not be sufficiently protective.
Another contaminant found in drinking water is perchlorate, a chemical used in explosives and rocket fuel. Estimates suggest that approximately 16 million Americans have detectable perchlorate in their drinking water supplies. Perchlorate interferes with iodine uptake in the thyroid gland and has been studied for its effects on thyroid function.
Pharmaceutical residues are also present in drinking water. There are currently no federal drinking water standards for pharmaceuticals in the United States, and conventional water treatment systems are not designed to remove them. Depending on treatment methods, studies have found that between 10% and more than 80% of pharmaceutical compounds may pass through water treatment unchanged.
Atrazine, a widely used herbicide, is among the most frequently detected pesticides in U.S. water systems. According to data from the Centers for Disease Control and Prevention, more than 75% of the U.S. population has detectable levels of pesticides or their metabolites in urine. Risk assessments by the Environmental Protection Agency have found that atrazine can cause reproductive harm in mammals, fish, and birds, with real-world exposure scenarios exceeding levels of concern by large margins. Atrazine remains one of the most commonly detected agricultural chemicals in surface and groundwater.
These examples represent only a small fraction of environmental chemical exposure. Even if all 91 regulated drinking-water contaminants are considered, they account for roughly 0.1% of the chemicals released into the environment. Biomonitoring data from the Centers for Disease Control and Prevention indicate that the average American carries more than 100 synthetic compounds in their body at any given time, many of which are not routinely monitored in drinking water.
