chromium

An example of a chromium compound (chrom(VI)-oxide)
user BXXXM - wikimedia commons

The Environmental Working Group (EWG) says it commissioned a study that tested tap water in 35 cities across the United States and found a cancer causing chemical in 31 of the cities they tested.

In Michigan, the EWG tested for evidence of hexavalent chromium in Ann Arbor's water supply and found the chemical at .21 parts per billion. The group says a proposed "safe" level in California is .06 parts per billion.

The group says: