Is Arsenic the Worst Chemical in the World?

June 3rd, 2012 by Steve

By Deborah Blum, June 1, 2012 

 “Arsenic is the number one environmental chemical for human health,”  Joshua Hamilton tells me during a recent phone call. We’re talking about his latest research, a just-published study in PLoS ONE  which found that this naturally occuring poison causes harm in an astonishingly small dose — 10 parts per billion.

Hamilton’s study looked at arsenic’s effect on mother mice and their offspring. But he chose the 10 ppb dose for a very human reason. It’s the safety standard the U.S. Environmental Protection Agency sets for arsenic in drinking water. Why does EPA need such a standard? Because an estimated 25 million Americans (mostly on private well systems) drink water contaminated by arsenic-rich bedrock. (I’ve put an arsenic map of the United States at the top of the post. Note that micrograms per liter is the same thing as parts per billion. This tells you that a lot of private wells — which are not held to public water supply regulations — run above the EPA standard.)

Global estimates of people drinking arsenic-contaminated water can run as high as half-a-billion people — and can also involve far more dangerous concentrations than in the United States. The classic — and tragic — example comes from  Bangladesh, a situation I described a couple years ago in a post calledHow to Poison a Small Country. In the 1960s, attempting to combat a cholera epidemic, aid agencies hit upon a plan of drilling wells across Bangladesh, tapping into bacteria-free ground water. They later realized that they had tapped into one of the most arsenic-contaminated aquifers on the planet, creating what WHO would later call the greatest mass poisoning of a human population in world history.

And I bring up Bangladesh because what happened there still matters, but also because the resulting toxiclogical discoveries connect directly to the work by Hamilton, a senior toxicologist at the Marine Biological Laboratory in Woods Hole, Massachuetts, and Courtney Kozal-Horvath of Dartmouth University’s medical school. Both are affiliated with Dartmouth’s Superfund Research Program on Toxic Metals.  And both have been focusing on arsenic for some years now because, as Hamilton puts it: “It just outstrips all the others”.

Before Bangladesh, arsenic was best known for its long history as a homicidal poison. An accessible and relatively abundant naturally occurring metalloid element, it didn’t take long for killers to make use of it, a story that simmers from the Borgias onward. Its use as a murder weapon started declining after 19th-century scientists figured out how to detect it in a corpse. But, as it turned out, there was a kind of environmental warning in how arsenic worked as a high-dose poison (lethal at about 70-200 milligrams). It had the ability to affect every cell in the body — it wasn’t like, say, mercury, mostly dangerous as a neurotoxin. No, arsenic wrought harm everywhere, killing cell by destroyed cell.

“In the 1960s, no one cared about arsenic and no one tested for it in environmental settings,” Hamilton says. “And then WHO began its well drilling program in Bangladesh. And then people started dying there of diseases they shouldn’t have been dying of.” In this poor country, where the diet was primarily rice, fish, vegetables,  people in Bangladesh started developing diabetes and heart disease. At far too young an age, they developed cancers usually associated with aging.  The poison’s destructive effects seemedlimitless. As Joseph Graziano at Columbia University would show in 2004,  chronic arsenic exposure was even contributing to reduced cognitive function in children.

Of course, the arsenic-contaminated water in Bangladesh is significantly above the accepted 10 ppb standard. Recognizing local realities, the government there has instead set a 50 ppb standard but some well readings have been as high as 1000 ppb (or 1 ppm). Still even these are small numbers to produce such large effects. And so — thanks to this terrible, accidental experiment in human health — scientists around the world began to wonder about arsenic, not at its famously murderous high dose but at its low dose. Why was it so potent in such tiny amounts? And what was the actual safe level for arsenic?

And that brings us back to the Hamilton and Kozul-Horvath study published Thursday in PLoS ONE. Both researchers had been studying arsenic’s low-dose effects for some time; Hamilton had reported on its ability to disrupt endocrine functions more than a decade ago. “Other endocrine disruptors work as mimics,” Hamilton says. “They look enough like estrogen to bind to a receptor and turn it on. Arsenic’s different. It affects all five steroid hormone receptors. Nothing else does that.” Three years ago, the two scientists collaborated on a study — also in mice — that showed that low-dose, chronic exposure to arsenic could cripple their ability to mount an immune system response to influenza. “We’ve been looking for edge of the table,” he said. “The edge at which we find no effect by arsenic.”

The just-published study did not accomplish that. Titled “Effects of low-dose drinking water arsenic on mouse fetal and postnatal growth and development,” it actually began as an attempt to develop a better mouse model for studying arsenic effects. The influenza study had been set at a dose of 100 ppb and the combination of the poison and the influenza had killed many of the mice. So the researchers dropped down to 10 ppb. This dose was given to pregnant mice in an effort to see if their offspring grew up into adults with compromised immune systems as well. “The original intent was to challenge them with influenza later in life but the vet said they were so compromised that we couldn’t do it,” Hamilton said.

Too many of the baby mice showed severe developmental delays — they were small, they were weak, they were unusually lethargic compared to offspring of mothers fed an arsenic free diet. The little mice were not being poisoned by arsenic — further investigation didn’t turn up noticeable levels in their mother’s milk or in amniotic fluid. What the investigation did find was that the arsenic-dosed mothers were not producing healthy levels of lipids (nutrient rich fats and fat-soluble vitamins) in their milk and blood. Their offspring were suffering from a kind of subtle malnutrition, apparently arsenic-induced. “So we’re still looking for that table edge,” Hamilton says.

It’s important to note here that mice aren’t a perfect model for human arsenic response. They metabolize it differently and are actually more resistant to it at higher levels than we are. But it’s also important to note that human exposures also see notable low-dose response to arsenic. And that this new study fits into an increasing body of work showing that arsenic can, indeed, be formidable at trace levels in many species. In that light, the EPA is discussing a review of that 10 ppb limit and whether it adequately protects public health.

I should also note here that although arsenic is a naturally occurring element, we humans amplify exposure through our own activities. It’s been used in agricultural pesticides for more than a hundred years. It’s a by-product of smelting, mining, coal burning and other industrial processes. And I should note that it’s impossible to avoid some arsenic exposure on this planet.

So is it just a risk we live with? Not entirely. There are ways to reduce exposure. For instance, Hamilton recommends getting your water tested if you draw from a private supply not regulated by the government. If you find risky levels of arsenic, then it probably makes sense to look into protective devises, such as installing a reverse-osmosis water filter. It makes sense that we ask that government agencies provide us with the best information possible on sources of arsenic exposure — both natural and industrial — and how to manage them.

And it makes sense that we ask our government agencies to pay attention here and come up with a unified safety standard for arsenic. Although the EPA has set a safety limit on drinking water, the U.S. Food and Drug Administration has so far not come up with anything comparable for arsenic in the food supply. Even though, as we know, many crops are watered with the very ground water we’ve been discussing here. And, even though, some imported products, such as apple juice from China, have been found to carry a fairly high level of arsenic.

“We need to put pressure on our federal agencies to come up with a universal standard,” Hamilton says. “It’s not enough for them to just say ‘trust us.’ We deserve better than that.” And to that, may I just say, Oh, agreed. We deserve much better than that.

Filed under: Arsenic Testing, General

© Copyright 2023 AlpHa Measurement Solutions LLC. All Rights Reserved. Web Design and Development by Interthrive