Basic Profile


Arsenic is a metal that has no smell or taste. Arsenic is naturally present in bedrock in many places throughout CT and RI. When a drinking water well is drilled into bedrock containing arsenic, the arsenic can get into the well water. We know that there are private wells in locations across CT with high levels of arsenic.


Arsenic can occur naturally in soil and bedrock in many parts of the United States. Arsenic can also be present due to human land use and industrial activities. Arsenic has been used in some pesticides and as a wood preservative. The use of arsenic in pesticides has largely been discontinued, but there is still the possibility that arsenic has built up in the soil where it was once used.

Health Effects

The EPA and expert scientific committees have classified arsenic as a human cancer-causing agent. Research indicates that people living in areas where water concentrations are very high are more likely to have bladder, lung, or skin cancer. They are also more likely to have problems with their skin, and with their cardiovascular, immune and neurological systems. These toxic effects of arsenic exposure develop after many years of exposure.

When to Test

You should test for arsenic when you buy a house with a well or at the time a new well is drilled. It is possible for arsenic levels in well water to fluctuate so even if one arsenic test shows no arsenic problem, it is a good idea to test for arsenic every 5 years. If you have a treatment system to remove arsenic from your water, you should test every year to be sure your treatment system is working properly.

How to Treat Wells Contaminated with Arsenic

Removal of arsenic from well water can be a complicated process. If your water has high arsenic, we recommend that you consult a knowledgeable water treatment specialist. There are several treatment technologies that can remove arsenic from well water. These technologies include metal oxide filters, ion exchange systems and reverse osmosis systems. However, the chemical parameters of your well water and the chemistry of the arsenic present in your water will dictate which treatment technology will effectively remove the arsenic. This is why it is important to involve a water treatment specialist.