High levels of dioxins, chemicals linked to birth defects and cancer, might have washed away from a Houston-area Superfund site after a cap meant to contain contaminated sediment was damaged during flooding from Hurricane Harvey, the Environmental Protection Agency said.
The agency said a water sample near the exposed area of the fabric-and-rock cap at the San Jacinto River Waste Pits found dioxins at more than 2,300 times the level that would trigger a cleanup.
WHAT ARE DIOXINS?
Dioxins are a group of toxic chemical compounds formed primarily during burning and many industrial activities, including trash incineration, coal-fired power generation, chlorine bleaching of pulp and paper, copper smelting and cement-making.
Dioxins stay in the environment for a long time, building up and becoming more dangerous as they move up the food chain.
WHAT ARE THE HEALTH RISKS?
The most common and dangerous dioxin — TCDD, an ingredient in the Vietnam War-era defoliant Agent Orange — is linked to lung cancer and non-Hodgkin's lymphoma.
High levels of dioxins also have been linked to many other health problems, including birth defects, heart disease and diabetes. But even low levels can cause a host of problems, including skin and gastrointestinal issues.
HOW ARE PEOPLE EXPOSED?
Everyone is exposed to dioxins in food, air and water, and those who handle pesticides and herbicides also may be exposed.
People who live near hazardous waste sites, incinerators and factories can be exposed to high levels. A concern of residents near the San Jacinto River Waste Pits Superfund site is that dioxins don't dissolve easily in water, and can be washed away in contaminated sediments and deposited over a wider area.
Sources: National Institutes of Health, Agency for Toxic Substances and Disease Registry