Chloromethane
Overview
Chloromethane, also called methyl chloride, is an industrial chemical, and EPA classes it as one. It occurs naturally in seawater as well as reaching water from industry. EPA monitored it nationwide in 2013 to 2015 and has set no limit for it.
In Florida, Chloromethane was found in 16 community water systems serving about 1,444,290 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; natural formation in oceans; some combustion.
The standards
Enforceable. A utility must stay at or under this.
Health-based, not enforceable. Often lower than the limit, sometimes zero.
EPA Reference Concentration (UCMR 3), Contaminant Information Sheets for the Final CCL 4. EPA sets this on a cancer endpoint: it is the level EPA associates with a one in a million lifetime cancer risk. It is not a legal limit and no utility is required to meet it.
Health effects the EPA associates with it: EPA's reference concentration for chloromethane is based on a cancer endpoint. The figure of 2.69 ppb is the level EPA associates with a one in a million lifetime cancer risk.
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
It is volatile, so aeration strips it and activated carbon adsorbs 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
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.