Arsenic in Well Water
Arsenic comes out of the rock, not from anything anyone did. It is common in Michigan, the West and parts of the Northeast, it has no taste, and long exposure raises cancer risk. A single test tells you where you stand.
Likely causes
- Naturally occurring arsenic in bedrock aquifers
- Old orchard land treated with lead arsenate
- Mining areas
Tests to order
- Arsenic total
- Iron
- pH
- Manganese
Treatment options
- Point-of-use reverse osmosis
- Whole-house adsorption media
- Oxidation plus iron filtration when iron is high
The 10 ppb line
The federal limit is 10 micrograms per liter, written as 10 ppb. Wells in glacial deposits and certain bedrock run well past it in parts of Michigan, Minnesota, New Hampshire, Maine, Arizona, Nevada and the Front Range. Long-term exposure is linked to skin, bladder and lung cancers and to cardiovascular disease. There is no smell, color or taste at any level found in wells.
Testing once is not enough
Arsenic levels shift with pumping rate and season, so a well that reads 8 ppb in spring may read 14 in late summer. Test twice in different seasons before deciding. Ask the lab for iron and pH on the same sample, because they determine which treatment works.
Treat the water you drink, or all of it
For most homes, a reverse osmosis unit under the kitchen sink removes 90% or more of arsenic from drinking and cooking water for $300 to $800. Whole-house treatment uses adsorption media such as iron-based granules in a tank, $1,500 to $4,000, replaced every one to three years depending on the level. If iron is also high, an oxidizing iron filter removes a good share of the arsenic along with it.
Is it safe to shower in arsenic water?
Yes. Arsenic is not absorbed through skin and does not vaporize. The risk is only from drinking and cooking.
Will boiling or a Brita filter remove arsenic?
Boiling concentrates it. Standard pitcher filters do not remove it unless specifically certified for arsenic under NSF 53 or 58.