Chromium-6 (hexavalent chromium)
Overview
Chromium-6, or hexavalent chromium, is one form of chromium and the dangerous one. It reaches water from industrial discharge, from cooling towers and plating works, and from natural deposits. There is no federal limit for chromium-6 itself. It is covered only by the limit on total chromium, which counts every form together, so a system can meet that limit with most of its chromium in this form. EPA monitored chromium-6 nationwide in 2013 to 2015 and issued no reference concentration for it, noting its own assessment was still in progress.
In Florida, Chromium-6 (hexavalent chromium) was found in 215 community water systems serving about 18,555,800 people. Nobody has set a legal limit for it, so no reading here counts as an exceedance and no utility is required to do anything about it.
Where it comes from: Industrial discharge; plating, tanning and cooling tower treatment; erosion of natural deposits.
The standards
Enforceable. A utility must stay at or under this.
Health-based, not enforceable. Often lower than the limit, sometimes zero.
California OEHHA PHG (2011).
Health effects the EPA associates with it: California's public health goal for chromium-6 is 0.02 ppb, which is the level its health agency considers to carry no significant risk over a lifetime. EPA published no reference concentration for it in its national survey because the agency's own assessment was still in draft.
The health goal is set on health alone. The legal limit is set as close to it as is technically and economically feasible, so treatment cost and available technology are written into the number a utility is measured against. A system at or under the limit is meeting the standard it is required to meet. Both numbers are shown so the distance between them is visible.
What removes it
Reverse osmosis removes it. Anion exchange also works, because chromium-6 carries a negative charge in water, which is what makes it mobile and hard to hold onto in soil.
Treatment guidance describes the methods generally used for this contaminant. What your own tap actually carries depends on your plumbing and your service line as much as on the utility, which is what a test at the house tells you and an annual report cannot.
Where in Florida
Highest reported levels
Showing the 25 highest of 215 systems that reported Chromium-6 (hexavalent chromium).
Data Sources
These figures describe water as delivered by each utility, not what your home’s plumbing adds after it arrives. Informational; not a substitute for testing your own tap.