By Stephanie Soucheray

Since February, when a leak from a coal ash pond near Eden spilled tens of thousands of tons of the waste into the Dan River, there’s been a lot of talk about the toxins in coal ash.

We assume that water exposed to coal ash is unsafe to drink unless treated, but why? What are those elements, and how, exactly, do they affect the health of humans?

Using the Agency for Toxic Substances & Disease Registry (accessed through the CDC) and the EPA’s peer-reviewed Human and Ecological Risk Assessment for Coal Combustion Wastes, we compiled the chart below to help answer these questions.

Congress passed the Safe Drinking Water Act in 1974, which requires the EPA to determine the level of contaminants in drinking water wherein adverse health effects are unlikely to occur. Coal ash can contain dozens of heavy metals, organic and inorganic compounds and contaminants. Below are the seven most troublesome for human health.

According to testimony given by Paul Newton, president of Duke Energy’s operations in North Carolina, to the General Assembly on Tuesday, old restored coal ash ponds now house “robust” ecosystems.

“Coal ash ponds are not all they appear to be sometimes,” Newton said.

But even if toxins in coal ash occur in miniscule amounts, the toxins below – all contained in coal ash – can still cause problems for humans who have regular exposure to them.


ArsenicA known poison, this is what’s used to kill rodents. It can kill humans too, but only in extremely high doses.

Long-term exposure to low doses, however, is a problem because at low levels arsenic is a known carcinogen. Humans exposed to low levels of arsenic in drinking water over long periods of time have been found to have higher incidences of skin cancer and cancers of the kidney and bladder.

Right now, the EPA standard for arsenic in drinking water is 10 parts per billion (ppb) of water. That’s the equivalent of 10 drops of water in an Olympic-sized swimming pool.

For years, the standard was 50 ppb, but the standard proposed for a 2005 update was actually 5 ppb. Because arsenic occurs naturally in many water systems (especially in desert areas), the Environmental Protection Agency allowed for slightly higher levels of arsenic to occur in water. Otherwise, cleaning all the arsenic out of public water systems would be prohibitively expensive for many consumers and water agencies.

Recent studies have shown that children exposed to arsenic are more likely to have lower IQs than unexposed peers.


CadmiumMore dangerous when its inhaled rather than ingested, cadmium only poses a real threat to humans if it reaches the lungs. It can cause emphysema, kidney disease, high blood pressure and lung cancer.

More likely, the EPA states that chronic exposure to low levels of chromium is linked to kidney damage. The maximum contaminant level for cadmium is 5 parts per billion, the equivalent of five blades of grass on a football field. Cadmium is bioaccumulative, and plants, including tobacco plants, are some of the most common conduits of contaminated soil.


CopperToo much of this heavy metal causes gastrointestinal distress in short-term exposure.

Some people may already be exposed to levels of soluble copper in drinking water that are above the acceptable drinking water standard of 1,300 parts copper per billion parts (ppb) of water, about a quarter cup of copper in an Olympic sized swimming pool. That really only happens if your water is corrosive and you have copper plumbing and brass water fixtures. On average, the concentration of copper in tap water ranges from 20 to 75 ppb.

Usually, the concentration of copper in lakes and rivers ranges from 0.5 to 1,000 ppb, with an average concentration of 10 ppb.

If you drink water that contains higher than normal levels of copper, you may experience nausea, vomiting, stomach cramps or diarrhea. High intakes of copper over the short term can cause liver and kidney damage and even death.

Long-term, drinking water tainted with leached copper can increase the risk of kidney disease and liver problems.


ChromiumIf chromium gets in drinking and ground water, stomach ulcers, nausea and general gastrointestinal distress can follow. Frequently, ingesting chromium has been linked to stomach cancer and chronic ulcers.

If human skin comes into contact with highly contaminated water, dermatitis and irritation can follow.

Currently, the EPA’s limit is 0.1 mg/L or 100 ppb. However, that number was called into question in 2008 and the EPA is currently reviewing literature that suggests that at 100 ppb chromium could be carcinogenic.


LeadLike arsenic, lead has been a known poison for years, and there is no safe or recommended level of lead exposure. Lead is extremely dangerous to the nervous system. High levels of lead in drinking water can cause kidney disease, brain swelling and nervous system disorders. Lead exposure can cause miscarriages, raise blood pressure and cause systemic weakness in the hands and feet. Children are especially vulnerable to lead poisoning.

Fortunately, most lakes, streams and rivers have very low levels of lead: The EPA states that there are on average 5 parts of lead per billion parts of water in our drinking-water supply. Acidic water supplies increase the likelihood of lead exposure, as older pipes containing lead could be corroded. The EPA did not ban lead in consumer goods, including plumbing parts, until 1978, and it wasn’t until 1991 that it published the Lead and Copper Rule, which aimed to control lead in drinking water.

In January, the EPA revised the Safe Drinking Water Act to further limit the chance of lead exposure via drinking water. The new maximum allowable lead content of pipes, plumbing fittings and fixtures is 0.25 percent.


MercuryThe maximum contaminant level of mercury is 0.002 milligrams per Liter (mg/L), or 2 ppb, the equivalent of 2 drops of mercury in an Olympic-sized swimming pool.

The EPA reports that people drinking water contaminated with more than that amount of mercury over long periods of time can suffer kidney damage. Blood pressure and heart rate increase with mercury exposure, and consuming mercury-tainted water can cause an upset stomach.

Mercury is bioaccumulative, meaning that fish exposed to it store the metal in their gills and amounts increase as it travels up the food chain. Because mercury is so poisonous to developing nervous systems and organs, pregnant women must be extra careful not to consume water or seafood tainted with mercury.  High levels of mercury have been linked to low IQs, mental retardation and developmental delays in children exposed in utero, as well as central nervous-system disorders and blindness.

The EPA recommends that lakes, rivers and streams contain no more than 144 parts mercury per trillion (ppt) and is currently reviewing water quality criteria for mercury.


SeleniumWe all need this trace element to live, and most over-the-counter multivitamins contain around 50 to 70 micrograms per day (less than 1/1,000th of a baby aspirin).

But there can be too much of a good thing. Like mercury, selenium is bioaccumulative. If humans ingest more than 500 mcgs per day (about 1/150th of a baby aspirin), they are at risk for hair loss, skin problems and nervous-system disorders. Fish are the most likely route for human exposure.

Recently, a long-term study of men taking 200 mcgs of selenium daily showed they had higher rates of aggressive prostate cancer then men taking a placebo.

The EPA’s maximum contaminant level is 50 ppb in drinking water.

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