Heavy Metals in Water
Lead, arsenic, chromium-6 in tap water
What is it?
Tap water carries several heavy metals as a result of ageing infrastructure, industrial contamination, and natural geological sources. Lead enters water primarily through old service pipes and household plumbing installed before 1986, when lead solder and lead pipes were commonplace. Arsenic occurs naturally in geological formations and is concentrated in groundwater in many regions. Chromium-6 enters water through industrial discharge. The US EPA estimates 9.2 million homes are still served by lead pipes. These contaminants produce no taste, odour or colour, making them detectable only through testing.
What it does to your body
Neurodevelopmental harm (lead)
There is no established safe level of lead in children. Even low blood lead levels are associated with reduced IQ, ADHD, and behavioural problems. The CDC considers blood lead levels above 3.5 micrograms per decilitre as requiring clinical attention.
Cancer (arsenic, chromium-6)
Long-term arsenic exposure is a leading cause of environmentally caused cancer globally, linked to bladder, lung and skin cancers. Chromium-6 is classified as a human carcinogen.
Cardiovascular disease (lead)
Adult lead exposure is associated with hypertension and increased cardiovascular disease risk, even at blood levels previously considered safe.
Kidney damage
Both lead and arsenic are nephrotoxic, causing chronic kidney damage at levels commonly found in contaminated water supplies.
Cognitive impairment in adults
Research has found associations between chronic low-level lead exposure and cognitive decline in older adults.
How widespread is the problem?
The NRDC estimates that over 63 million Americans were exposed to unsafe drinking water between 2016 and 2019. The most contaminated systems are in older Midwestern and Northeastern cities. Well water users face arsenic contamination risks that vary significantly by region. EWG testing found chromium-6 in tap water serving 218 million Americans.
Where it hides in your home
Key research
EPA Lead and Copper Rule Revisions
EPA update requiring water utilities to identify lead service lines and begin replacement, and lowering the action level for lead. Acknowledges 9.2 million lead service lines still in use.
Lanphear et al. Low-level lead exposure and mortality
Published in The Lancet Public Health: found that low-level lead exposure accounts for an estimated 412,000 premature deaths annually in the US, predominantly from cardiovascular causes.
EWG Chromium-6 in US Tap Water
EWG testing found chromium-6 in drinking water serving 218 million Americans, often at levels above the health guideline, despite the compound having no national enforceable standard at that time.
Lead accumulates in bone tissue and has a biological half-life of decades. Arsenic accumulates in hair, nails and skin. The priority is eliminating ongoing exposure through water filtration, not waiting for natural clearance. Children and pregnant women are at highest risk from ongoing exposure.