You are here:  Body of Evidence ReportThe ChemicalsArsenic   
 Arsenic Minimize

Arsenic is a common element in the earth's crust, occurring naturally in soil and bedrock. Many people in Maine are exposed to arsenic by drinking contaminated water from bedrock wells. In eastern New England, 20-30% of private wells exceed the arsenic drinking water standard of 10 micrograms per liter. Arsenic has also been used in pressure-treated lumber, is still used in industrial applications, and can still be found in decks, playgrounds, and other structures. Arsenic was used as a pesticide in Maine between 1920 and the late 1960s, and high arsenic levels can still be found in areas of Maine where arsenic-containing pesticides were applied to apple orchards, potato and blueberry fields, and along roadways.

Arsenic in public water supply wells, mg/L.
Source: ME Drinking Water Program
Arsenic in Maine People

The Maine participants exhibited a wide range of arsenic levels in urine. The median level of total arsenic in Mainers (30.7 ppb) was about three times higher than the median level reported in a study published in the scientific literature (see Table 3). This might be due to relatively greater reliance in Maine on drinking water wells contaminated with highly toxic inorganic arsenic, or could represent recent consumption of seafood, which contains an essentially nontoxic, organic form of arsenic. (See Box on Arsenic’s Complex Chemistry).

Five of the Mainers exhibited above normal total arsenic exposure levels of greater than 50 ppb in urine (see Figure 7 and Table 2). One of the participants approached the total arsenic exposure level considered excessive (without consumption of seafood) at 100 ppb in urine.

Another participant, Regina Creeley, had the highest level of total arsenic at 839 ppb. Regina reported that she ate a large meal of mussels prior to her test. Certain seafood including shellfish contributes large amounts of a non-toxic organic form of arsenic to a total arsenic measurement in urine. (See discussion in Box).

[BOX – Arsenic’s Complex Chemistry
The arsenic story is complicated. We measured total arsenic, which includes at least five different types of arsenic: the two most toxic forms of inorganic arsenic – arsenic(III) and arsenic(V); two somewhat less toxic, organic forms of arsenic formed in the body after exposure to inorganic arsenic, monomethylarsinic acid (MMA) and dimethylarsinic acid (DMA); and arsenobetaine – the nontoxic form of organic arsenic found in shellfish and some other seafood. We also measured total inorganic arsenic, arsenic(III) plus arsenic(V), and we separately tested for the most toxic form of inorganic arsenic, arsenic(III). We did not measure for MMA, DMA, or arsenobetaine.

When people are exposed to highly toxic inorganic arsenic (from well water or old pressure treated wood, for example), that arsenic is metabolized in the body. In just a few days, this biologically transformed arsenic is mostly excreted in urine as, on average, 10 to 30 percent inorganic arsenic As(III) and As(V), 10 to 20 percent MMA and 55 to 76 percent DMA. [Note: As(III) is the abbreviation for arsenic(III) and As(V) is short for arsenic(V)].

This complex biochemistry and the limits of our testing mean that our results underestimate exposure to toxic inorganic arsenic by a factor of three-fold to ten-fold. And, we can’t tell how much of the exposure to organic arsenic, which is high for several Mainers, is due to MMA and DMA (reflecting exposure to toxic inorganic arsenic) and how much is due to the nontoxic organic arsenic from seafood, arsenobetaine, which is passed through the body without being absorbed.]

While three participants obtained more than 90% of their drinking water from a private well, this was too small a group to show a relationship between urinary arsenic levels and well water consumption by geographic area, and participant wells were not tested for this project.

Denyse Wilson had the highest inorganic arsenic level in the group, and her total arsenic level was also above the normal exposure level. Denyse does not use well water, but she does eat herbs and vegetables from a raised-bed garden built in the spring of 2006 using purchased soil and older pressure-treated wood. Follow-up testing of arsenic in the soil and municipal water supply is pending. Lauralee Raymond also had a relatively higher inorganic arsenic and total arsenic result.

Figure 7: Total arsenic and inorganic arsenic levels, measured in urine. The top horizontal line is the above normal exposure of total As (50 ppb; Klaassen 2001); the bottom line is the national median for total As (10.23 ppb).

HEALTH EFFECTS: Potent Cancer-Causing Agent

Long-term exposure to low levels of arsenic in drinking water has been linked to bladder, lung, kidney, liver, prostate, and skin cancer. The higher the level of arsenic in the water, the greater the cancer risk, and cigarette smokers who drink arsenic contaminated water are the most at risk. Maine has one of the highest rates of bladder cancer in the United States. Arsenic can also harm the nervous system, heart and blood vessels. EPA classifies arsenic as a human carcinogen. Because their bodies are less efficient at processing arsenic, children may be more susceptible. Arsenic can cross the placenta and has been found in fetal tissues. Research suggests long-term exposure to arsenic in children may result in lower IQ scores.

Policy Changes Needed

Maine needs a law to require routine testing of private well water for arsenic, especially when a home is sold or rented. The prevalence of arsenic in Maine groundwater, the potent carcinogenicity of arsenic and the unacceptably low level of public awareness of the arsenic threat, make this an urgent public health issue.

Publicly accessible institutions with old pressure-treated wood structures, such as decking, railings and playground structures, should be required to replace them with arsenic-free construction. If replacement is not economically feasible, then the arsenic-treated wood should be coated with a sealant on an annual basis to reduce arsenic exposure on contact with the wood.

Reducing Your Exposure to Arsenic

Test your well water. Well water is a major source of arsenic exposure in Maine. Arsenic-contaminated drinking water does not smell, taste, or look different; the only way to find out if your well has arsenic is to have your water tested by a certified laboratory. The longer water sits in a well, the more time there is for arsenic to dissolve into drinking water, so wells used by seasonal homes and camps may have higher levels of arsenic. If your water comes from a public supply, contact your local water district for the most recent arsenic test results. Treatment (or even drilling a new well) is required to remove arsenic from drinking water. As of January 2006, the maximum amount of arsenic allowed in public drinking water systems is 10 parts per billion (0.010 mg/L), a level probably not sufficiently protective of public health.

Replace old pressure-treated wood structures. Maine was among the first states to ban the sale of arsenic-treated wood used in playgrounds and decks in 2003, around the time that a national voluntary ban was negotiated. If you can afford it, remove and replace pressure-treated wood structures installed before 2004. These include boards used for vegetable gardens, playgrounds, decks and railings.
Avoid sawing pressure-treated wood. Paint or seal all arsenic-treated wood with a penetrating oil deck treatment. To learn more about what to do if you have pressure treated wood at home, visit


Home | Body of Evidence Report | Campaigns | Resources | Healthy Homes | News & Events | Get Involved!
  Copyright © 2013 by the Alliance for a Clean and Healthy Maine   Login      Site by Planet Maine