Governor Chris Sununu on Friday signed a bill adopting a stricter limit on arsenic in the state's drinking water.
The new standard will require local water systems, landfills and others to limit how much arsenic they allow in the water supply to 5 parts per billion – half the federal default.
New Hampshire is only the second state in the country to make such a change, after New Jersey.
The Department of Environmental Services based the new law partly on a recent UNH study, which says the change will help state residents avoid dozens of cancer cases, a handful of deaths and other negative health and economic outcomes in the coming decades.
New Hampshire gets most of its drinking water from groundwater that can contain high levels of naturally occurring arsenic. Past research from Dartmouth College suggests this is one reason the state has some of the nation’s highest rates of certain cancers, such as bladder cancer.
This research also suggests arsenic exposure may be linked to heart disease and diabetes.
New Hampshire’s new arsenic standard must take effect within two years. The state says it’ll cost municipal and school district water systems about $2.6 million overall to adopt in the first year, and about $1.4 million each year after.
About half of New Hampshire residents use private wells, which aren’t required to follow the new regulation. Officials say those private well users are still strongly encouraged to test their water regularly and follow state guidance for treatment.
A DES fact sheet says as of 2010, 20% of the state’s many public and private drilled wells – the most common source for drinking water – had arsenic levels above 10 parts per billion, which is the state’s old standard.
Dartmouth research says about a third of the public water systems in New Hampshire contain detectable levels of arsenic.