Each year, cities across the United States publish water quality reports to reassure residents that their tap water is safe. These consumer confidence reports list the presence of specific contaminants, how those levels compare with federal safety standards, and what steps were taken to ensure compliance with regulations.
The City of Cambridge provides detailed information about its water source, treatment process and testing results. At first glance, the data feels thorough and reassuring. Cambridge draws its water from the Hobbs Brook and Stony Brook reservoirs. The treatment process includes ozonation, coagulation, filtration and disinfection. The city adds chloramine, a compound of chlorine and ammonia, to keep water clean as it moves through the distribution system. According to the most recent report, levels of disinfectants, bacteria, lead, copper and other regulated substances fall within the “acceptable” range set by the Environmental Protection Agency.
The city also offers free testing kits for lead and copper. Residents can get one at the Fresh Pond Water Treatment Facility and test their own tap water, which is recommended particularly for those who live in older homes, where pipe corrosion is more likely. This effort is important, especially in a city with historic housing stock in which lead exposure can occur from interior plumbing rather than from the water source itself.
But beyond lead and copper, most residents do not test their water. And Cambridge doesn’t offer free kits for anything else. This raises a quiet but important question: What else might be in the water?
Municipalities are required to test only for contaminants regulated under the federal Safe Drinking Water Act. This list of roughly 90 substances is focused primarily on microbiological threats, heavy metals and industrial chemicals already known to pose serious health risks. Most emerging contaminants are not on the list.
Take pharmaceuticals. Over-the-counter drugs, prescription medications and hormone treatments often enter wastewater systems and return eventually to natural water sources. Studies have detected trace levels of antidepressants, antibiotics, painkillers and birth control hormones in rivers and lakes across the country, but there is no federal requirement to test for them in drinking water.
The same is true for many pesticides and herbicides. While certain agricultural chemicals are regulated, hundreds are not studied, or are insufficiently studied. Chemicals applied to lawns, golf courses and landscaped public spaces can enter water systems through runoff. Cambridge contains and is near several golf courses and suburban green spaces. A peer-reviewed study published in the NIH-backed journal Environmental Health Perspectives found an association between residential proximity to golf courses and increased risk of Parkinson’s disease. While proximity does not equal causation, it underscores how environmental exposure pathways deserve closer scrutiny.
Then there are PFAS, often referred to as “forever chemicals” because they do not break down in the environment. Found in nonstick cookware, stain-resistant fabrics and firefighting foam, these chemicals have been detected in drinking water supplies across the country. Massachusetts has adopted stricter standards for them than the federal government, and Cambridge tests accordingly. Still, testing is limited to specific compounds and intervals. Residents who want broader screening must pay for private laboratory analysis.
Disinfection byproducts such as trihalomethanes and haloacetic acids form when chlorine interacts with organic matter in water. These compounds are regulated and monitored locally, but their presence is expected in treated water. Research continues on the long-term effects of cumulative, low-dose exposure, particularly when combined with other trace contaminants.
Why don’t cities test more?
The simple answer is cost. Testing for pharmaceuticals, microplastics, PFAS and emerging threats requires advanced lab equipment, trained analysts and strict protocols. The expense is significant, especially for contaminants that are not officially regulated. Municipalities follow federal law, and unless that law expands – which is increasingly unlikely – testing will remain focused on the known, not the possible.
That can leave residents in a gray area: While the water coming from the tap may meet legal standards, those standards do not always align with evolving scientific knowledge or personal comfort. The full list of what might be in a glass of water, though likely at trace levels, is longer than most people realize. The question is not only about what is in the water report. It is about what is missing from it.
Our water may be safe by regulation. Whether it meets personal standards is a different conversation and one worth having.
Julie Mahdavi is a health care and life sciences program leader at the Cambridge Health Alliance who has a master’s degree in global public health from the Imperial College School of Medicine in London. She can be reached at jmahdavi@csindie.com.
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