Selenium
Overview
Selenium is a naturally occurring element that is essential in tiny amounts but harmful at high levels.
In Florida, Selenium was found in 163 community water systems serving about 489,328 people. It was measured by 1,559 systems in all, so it was detected in 10% of the systems that tested for it.
The highest reading relative to the limit was at Altha, Town of Water System in Calhoun County, at 22% of it.
Where it comes from: Erosion of natural deposits; discharge from mines; runoff from farms.
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 (2010). For comparison the legal limit is 50 ppb.
Health effects the EPA associates with it: Hair or fingernail loss, numbness in fingers or toes, and circulatory problems.
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 or anion exchange. Carbon does not remove it.
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 163 systems that reported Selenium.
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.