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The Smallest Victims
of Arsenic

How a poison in our water reveals a missed opportunity
 

Author: Bruce Lanphear, MD, MPH

NOTE: This article was originally published on November 11,  2025 by Plagues, Pollution & Poverty on Substack. 


Reducing arsenic in our water may be one of the most direct—and overlooked—ways to prevent chronic disease.

Every year, hundreds of thousands of babies are born too small or too soon. Parents search for answers in genes or luck—but sometimes the culprit is closer to home. More than 40 million Americans drink from private wells—many of them untested and contaminated with arsenic or other toxic chemicals that can quietly raise the risk of premature or low-weight births.

Public-health victories rarely make headlines. Yet every so often, a new study reminds us not only how far we still have to go, but which direction to take. A study by Dr. Anne Nigra has done just that—linking arsenic in public drinking water to a greater risk of babies being born too small.

The finding is powerful on its own, but even more so in context. For centuries, arsenic has been known as a potent poison. At high doses, it kills quickly. At lower doses—those found in drinking water, food, and household dust—it works slowly, quietly increasing the risk of lung cancer, diabetes, and heart disease—three of the leading causes of death.

These aren’t rare or distant outcomes; they’re the illnesses that touch nearly every family, often without anyone realizing that a poison in  the water may have helped set them in motion.

What this new study adds is clarity: no level of arsenic exposure can truly be considered safe.

Beyond Safe: The Trouble with Thresholds

The federal drinking-water standard for arsenic in the United States is 10 parts per billion—about five teaspoons in an Olympic-sized swimming pool. But that number reflects politics, not health—and the science has left it behind.

Both New Jersey and New Hampshire have set their standards at a more protective 5 parts per billion. And for good reason. A growing body of research shows that even “low” levels of arsenic are linked to harmful effects, from impaired fetal growth to excess cardiovascular disease.

The idea of a “safe threshold” for toxic chemicals has always been more political than scientific. Arsenic is simply the latest example. The science keeps showing that small, chronic exposures add up—that the line between a harmless dose and a harmful one is thinner than most of us can imagine.

The Evidence Builds: Clues from Birth and Beyond

For most people, arsenic exposure doesn’t come from factories or mines—it comes quietly through the water we drink and the food we eat, especially rice. In much of the United States—and around the world—it occurs naturally in groundwater that supplies private wells, a hidden source of chronic exposure. Rice—which is a staple for half of the world’s population—absorbs arsenic from both water and soil more efficiently than most crops. Together, these exposures create a steady intake of arsenic in millions of people who may never suspect it.

Private wells, used by more than 40 million Americans, are not regulated under the Safe Drinking Water Act. Families who depend on them often have no idea what’s in their water. In rural and low-income communities, many drink what flows from their taps unaware it may contain arsenic, lead, PFAS, or other contaminants.

When the EPA lowered the federal arsenic standard from 50 to 10 parts per billion in 2001, not everyone agreed it was necessary. Senator Pete Domenici of New Mexico tried to block the rule, calling it unscientific and too costly for small communities. But time—and science—proved otherwise.

Using national biomonitoring data from 2003 to 2014, Anne Nigra found that arsenic exposure declined by about 17% among Americans on public water systems—equivalent to 2000 fewer cases of lung and bladder cancer each year. Levels, however, remained unchanged for families relying on private wells.

Policy works—when we let it. Even imperfect protections can save lives, reduce suffering, and remind us that progress, though often slow, still moves in the right direction when guided by evidence and public will.

A Global Crisis, Hiding in Plain Sight

The arsenic problem extends far beyond U.S. borders. In Bangladesh, where tens of millions rely on groundwater contaminated with naturally occurring arsenic, the crisis has been called the largest mass poisoning in history. Arsenic contamination threatens communities in India, China, Mexico, Chile, a