Friday, December 22, 2006

Radon: The Silent Intruder

Many of us here in Western Massachusetts worry about Vermont Yankee (our local, and famously old nuclear power plant). We ask the dentist, “Do the kids really need another x-ray?” and we balance the benefits of mammograms with the risks of radiation. Yet we ignore the radiation than in many homes seeps through basements, through the floorboards and the heating ducts, and into the rooms where our children sleep. We ignore the silent intruder: radon.

We ignore it – yet radon is estimated to provide many of us with over one half of our annual average radiation dose. It is an undisputed human carcinogen. It is an undisputed cause of lung cancer, considered by many health agencies second only to cigarettes. It is also one of the easier contaminants (unlike lead in old paint, formaldehyde in building materials or even mold) to rid from our homes.

At the urging of our lawyer, my husband Ben and I tested our future home just before signing the purchase and sale agreement. Friends and family were skeptical. “Oh radon,” said a family member, “it’s just another one of those scams, someone must be making money off it.” A friend suggested radon is one of those “don’t know, can’t tell,” issues when homes exchange hands. “Why bother to find out? Then you’ll be responsible,” they said.

Sure enough, when we tested our soon-to-be home, it was just a bit above the Environmental Protection Agency action level. This, when the current owners had “inadvertently” opened the window near our radon test can. We requested they allow us to run another – though I can just imagine those doors and windows accidentally flapping open now and again during that test period. In the end, the radon was high enough to ask the sellers to chip in for remediation -- yet low enough for me to rationalize my inattention to it several years later.

As a toxicologist, I know that there is a lot of science - toxicology studies, epidemiological studies, and risk analysis - that go into each and every EPA guideline, standard and action level. Very often politics and economics are mixed in as well.

I know when information on human exposure is unavailable for a chemical, as it often is, that animal models are used to help scientists develop standards, and when this happens, the EPA employs what are called “safety factors,” basically reducing the estimated “safe” dose often by up to as much as 100 times or more. Sometimes that is enough, and sometimes not.

But this is not the case with radon. There are unfortunately plenty of data on human exposure. Five hundred years ago early toxicologists and physicians described a disease of the lungs in mine workers who wasted away and died young. That disease is now known as lung cancer, and the primary suspect is radon. A recent study by the National Cancer Institute found that the rate of lung cancer deaths in underground miners is five times that of the general population.

Radon occurs naturally. It is produced when uranium present in most rocks (but more prevalent in some like granites and shales) breaks down. As a radioactive compound, uranium disintegrates or decays releasing progeny (or daughter) products such as radium, along with energy in the form of radiation. Very often the progeny are also radioactive. In this case, radium decays into radon gas. And so it goes, with radon decaying into polonium and other radioactive products, each releasing radiation as they decay or disintegrate.

Upon disintegration, in the case of radon and its progeny, the radiation released is primarily in the form of an alpha particle - or two protons and two neutrons - that has the potential to cause lung cancer. If a speck of dust containing a speck of disintegrating polonium landed on your hand, it is unlikely it would do you much harm. Unlike x-rays or gamma rays, alpha particles cannot penetrate your skin. However, should you inhale that speck of polonium-containing dust, or air containing radon gas, or any of the radon decay products, and they further decay in your lungs, then that alpha particle can penetrate the delicate membranes surrounding your lung cells and damage genetic material.

Radon for indoor air is measured in pico-Curies (pCi). In the ambient or outdoor air of the United States, the EPA estimates that concentrations of radon generally range from 0.2 to 0.7 pCi/Liter of air, with some locations in places like Iowa reaching 1.4 pCi/Liter year round. However, it is virtually impossible to predict concentrations in the home based on ambient concentrations, or the type of rocks and soil beneath a home. Some homes have very low levels of radon, near ambient concentrations, while others have whoppingly high concentrations, reflecting a combination of the subsurface geology, and specific characteristics of a home, including foundation type, and number of floors.

In the United States there was little public awareness of radon until the day in 1984 when Stanley Watras set off radiation alarms at the Pennsylvania nuclear plant where he worked. Turns out, his exposure was not from the plant but from his home, which measured upwards of 2,700 pCi/Liters in the basement.

In response, the EPA quickly initiated a public awareness program and set 4 pCi/L as a “non-enforceable” or voluntary action level, at which EPA advises mitigation. The level was based in part on guidelines developed a decade earlier to protect Colorado citizens’ homes that had been built on uranium mine tailings. But, according to Dr. R. William Field, an associate professor of Occupational and Environmental Health and Epidemiology at the University of Iowa, College of Public Health, who led one of the largest studies on residential exposure to radon gas and lung cancer in the United States, the “Iowa Radon Lung Cancer Study,” the EPA level of 4 pCi/L is “...not a health based guideline. The Iowa Study and both the North American and European Pooled Radon Studies noted an increased lung cancer risk for prolonged exposures at and below the US EPA’s action level.”

In other words, though the EPA would prefer we reduce concentrations in our home to ambient levels, at the time the action levels were set, 4 pCi/L was considered an achievable goal. But, according to William Bell, coordinator of the Massachusetts State Radon Control Program, “EPA believes that most homes in the US can be fixed to below 4 pCi/L cost effectively. The action guide, the point where you take action and the mitigation goal, the point at which you deem the repairs successful, are in our view, not the same.”

In our case the fix was relatively simple and standard. A thick layer of plastic sealed over our dirt-floor crawl space, a few PVC pipes tucked into the concrete basement floor and an outside fan. Though the most likely time for radon exposure was winter --when the warm air rises up and out of our homes, causing more air and any co-occurring radon to be literally sucked out of the ground and into our home -- much to the dismay of my husband Ben, we were instructed to run the fan year round. “It sucks up electricity,” he grumbled. “I hate hearing the hum of that fan.” I’ve since been informed by Dr. Field that a fan should draw no more than a 60-watt bulb and that only poorly installed fans make much noise.

Still, after five years of sucking our radon away, one construction project which required dismantling of the external pipe and removal of the fan, and a peace-making decision to turn the thing off each spring when we opened our doors and windows for good, the fan rebelled, refusing to budge when we flipped it on for the fall season. From the surly technicians, to put it kindly, who represented the company that installed it, I learned that replacing the fan would cost a few hundred dollars. Not wanting to spend the money and not wanting to deal with that particular company – at the time one of the few choices locally - the rationalizations began. I rationalized the radon away, blissfully unaware that the action level was technology, rather than health based. I practiced my own kind of “don’t know can’t hurt” toxicology, instead of reading the bountiful literature on the contaminant in my home, I concentrated on industrial contaminants in other people’s homes. Though I did occasionally crack open the windows in winter, whenever my thoughts returned to radon.

Until now. This past summer after using a roll of duct tape and my vacuum cleaner to unsuccessfully battle an army of sex-starved winged creatures who had invaded my son’s room, we were informed that the large beam upon which our living room rested for over a hundred years also served as a feeding ground for generations of termites. While replacing the beam, we discovered the “fresh air return” was not so fresh, coming primarily from the dreaded basement, rather than the first floor vents. Thoughts of basement air blowing throughout the house awakened my concern about the air quality in my own home.

This article is the result of that new respect for that invisible intruder. Radon is one of the few chemicals where there is little disagreement among scientists as to its danger. It is one of the few chemicals to which we are exposed that is not in some way associated with industry. And it is a chemical we can, if not rid from our homes, at least reduce without too much expense and effort.

After five years our radon fan is up and running and I have just received two radon test kits to retest the concentrations. This winter the windows in my office will remain closed, and I won’t worry so much about what’s blowing through that heat duct in my children’s room.

Radon Information in Massachusetts:

According to William Bell, in Massachusetts, a radon test kit costs about $20, and makes a great gift. K its can be purchased through the EPA website at or or at local hardware stores. There is only one certified site in the state of MA, which is AccuStarLabs, Should your home need remediation, according to Bell, quality remediation should run between $1500-2000. For further information about testing and mitigation contact the MA DPH Radon Hot Line; 1-800-723-6695.

Thursday, December 14, 2006

How About Tuna (with a dash of mercury?)

I search the pantry and the fridge for a quick nutritious dinner.

“How about tuna,” suggests Sophie, my youngest. Tuna is her favorite protein, besides cheese, cheese, peanut butter, and cheese.

“I haven’t had it since last weekend,” she adds, turning on the charm.

My concern is mercury. And these days, most of us are aware that there is plenty of it in both fresh water and ocean dwelling fish. For parents with young children who find tuna one of the few foods with protein that their youngsters will eat, the situation is particularly worrisome. As a mother of two and a toxicologist, environmental contaminants are of particular interest constantly intruding upon our lives, while at the same time presenting unfortunate but interesting examples of human impact upon the natural environment.

Mercury, like all metals, occurs in nature and is present in the earth’s crust. While natural sources of mercury include volcanoes and geologic deposits, as most folks know, mercury is also released into the air by other processes such as incineration of medical waste (for example, burning thermometers) and, more importantly, burning coal.

Although the role of mercury as a potent neurotoxicant (a chemical which impacts the brain) has been known for centuries, the exact mechanism by which it causes toxicity remains frustratingly elusive. The term “mad as a hatter,” for example, is thought to originate from early observations of mercury’s neurotoxicity on those in the business. In the 1800s and early 1900s mercury was used in the felting process of hat manufacturing, likely resulting in large exposures and crazy hatters. In modern days, mercury was responsible for the neurotoxic and teratogenic effects (impacts the developing fetus) observed in villagers of Minamata, Japan, in the 1950’s and now known as Minamata disease. The disease was first noticed in the village cats, consumers of discarded or dead fish. The cats apparently danced and stumbled around the village prior to dropping dead on the street. Eventually, the disease manifested in humans, and was traced to mercury which for decades had been released into the water by local industry and accumulated in the fish and shellfish of Minamata Bay.

But mad hatters and Minimata were caused by exposures to much greater concentrations of the metal than are present in the workplace and the environment today. Present concerns for public exposure to mercury involve tiny amounts - in the parts-per-million range – in fish tissues. But even at these very low concentrations (a part-per-million is approximately the concentration of ink when four drops of ink are released into a 55 gallon drum) there is increasing evidence of potential health impacts, particularly on the developing brain. And although release of mercury into the environment is more tightly controlled, it is still released by industrial incinerators and coal-burning power plants (in 2005, the EPA issued its first ever rule to permanently reduce and cap mercury emissions.)

Once released into the atmosphere mercury may travel across state and country lines before it eventually settles and is transformed from metallic mercury into other forms including highly toxic methylmercury. It is this form of mercury, methylmercury that becomes incorporated into the diet of aquatic creatures and those that eat them.

Here is where the tuna comes in. We all know the story, big fish eat little fish, and bigger fish eat those fish. Big fish include tuna, swordfish and other large ocean species, as well as some freshwater species including lake trout and largemouth bass. Methylmercury concentrates as it moves up the food chain. Generally the larger older predators tend to have the greatest concentration of mercury in the flesh. This is why the EPA and FDA suggest that pregnant or nursing mothers and young children stay away from large predatory fish. According to the EPA, ingestion of chunk light tuna should be limited to 12 ounces a week, while albacore tuna should be limited to 6 ounces. Albacore tuna is a different fish than the tuna used for chunk light, which can be skipjack tuna and in some cases yellowfin tuna. Differences in the size, age and life histories explain the difference in accumulated mercury.

I pull a 6 ounce can of chunk light from the shelf, and hand it to Sophie. It is sad that we need to consider “how much,” of a contaminant we’re willing to ingest, or expose our youngsters to, but until mercury emissions into the environment are fully controlled if fish is part of your diet, then it’s a necessary consideration.

If you want to learn more, there are many good sites that provide greater detail on mercury in fish, mercury toxicity and mercury controls that you may want to explore:

EPA sites:; Physicians for Social Responsibility:; MA Department of Environmental Protection: Specific fish advisories for freshwater fish in the state may be found by searching:

Friday, December 08, 2006

Antimicrobials: Too Much of a Good Thing?

What do my husband’s armpits, my son’s sandals, my mother’s steak knives and my daughter’s hairbrush all have in common? Antibacterials. They are all impregnated with antibacterial chemicals – well maybe not the armpits, but the underarm deodorant. These days, just about anywhere that is suitable for bacteria is apparently also suitable for antibacterial treatment by manufacturers wishing to attract health-conscious shoppers.

But here’s the rub – antibacterial chemicals are now showing up in the environment – in places they were never meant to be. In water flowing into rivers downstream from sewage treatment plants, in fish, and in treated sewage sludge that is applied to agricultural crops.

Additionally, while it’s clear that the use of antibacterials are beneficial in clinical settings, according to a Food and Drug Administration panel on Nonprescription Drugs there is little or no indication that such additives protect the consumer any better than washing with plain soap and water.

As a one-time teacher of microbiology, I’d always prided myself on having the foresight to stay away from purchasing soap products with antimicrobials. Although to my surprise, there they were in other household I’d purchased including the Teva sandals and the Old Spice Classic with triclosan that I’d bought for my husband.

“[The antibacterials] triclocarban (and triclosan) were introduced in the hay-days of chlorine chemistry, when chemicals like DDT and PCBs were considered safe. Relative to the latter, the antimicrobials are less problematic, but now that PCBs and DDT are banned, the focus has shifted to other chlorinated chemicals like triclocarban and triclosan,” says Dr. Rolf Halden, of Johns Hopkins University.

Recently, Dr. Halden’s group reported in the journal Environmental Science and Technology that the majority of triclocarban that is washed down the drain and into sewage treatment plants ends up in sewage sludge, which in turn may end up on agricultural fields.

His research reveals not only the persistent nature of the chemical (not unlike those other chlorinated chemicals now banned.) It also highlights the high volumes of these chemicals that are used by consumers and released into the environment. Halden’s group estimated that in their study area alone, more than one ton of triclocarban ends up in the environment (and on agricultural land – where it can be taken up by crops) each year!

While Halden is concerned about the release of the chemicals into the environment, Dr. Stuart Levy, the director of the Center for Adaptation Genetics and Drug Resistance at Tufts University, is concerned about the potential for antimicrobials to encourage development of antibiotic or drug resistant microbes.

Development of antibiotic resistance is an important survival mechanism for microbes, and soil microbes in particular. Soil is packed with microbes. They are part of what makes healthy soil healthy. Soil is also a fertile hunting ground for new antibiotics. In fact the first mass-produced antibiotic, penicillin was produced by a soil-dwelling microbe. What better way to stake one’s microscopic claim then to poison one’s neighbors? So soil microbes are constantly battling antibiotics produced by neighboring soil microbes. And in order to “keep up with the Jones’” or at the very least survive the Jones’ constant assaults, bacteria have become adept at developing antibiotic resistance.

The same can be said for the millions of bacteria that live on and in our bodies. When they are constantly exposed to antibiotics, it is possible that some will overcome, and develop antibiotic resistance. This is where the antimicrobials come in.

“We produced the original evidence that triclosan [a chemical simlar in structure to triclocarban] can lead to antibiotic resistance,” said Dr. Levy, “but while resistance to antibacterials has been found among bacteria outside the laboratory, they have not been linked to the use of triclosan.”

“Triclocarban is another antibacterial found in soaps. No one has looked at its mechanisms of action. There is clearly concern about the exposure to both of these antibacterials [causing antibiotic resistance], but in particular triclosan. The other antibacterials of concern are those under the heading of quaternary ammonium compounds like benzalkonium chloride. More and more data are linking resistance to this product with antibiotic resistance.”

So, antibacterials which have the potential to cause antibiotic resistance are released into the environment in huge quantities as a result of consumer use, and an FDA panel has concluded that antimicrobial products appear to be no more protective to consumers than soap and water. Who’s in charge of regulating this stuff?

Antimicrobials are regulated by both the FDA and the Environmental Protection Agency, depending upon their use, and claims made by manufacturers. EPA regulates antimicrobials when they are used as pesticides, for example to reduce odors in my son’s stinky Tevas, but FDA regulates them as drugs when used in something like the bottle of soft-soap that graces the bathroom sink at my daughter’s school. In either case – since triclosan and triclocarban were developed and registered at least thirty years ago, back when persistent chemicals weren’t known to be a problem, and antibiotic resistance hadn’t reared its ugly head – one wonders how today’s research has enlightened the regulators.

“Advances in a number of fields have changed the way we examine and interpret the potential risk of synthetic chemicals,” says Halden. “Many studies conducted in the 1970’s would not pass muster today.”

But there’s hope, according to Stuart Levy, who noted that while “there is no evidence of a change in regulation, there certainly seems to be a greater insight and concern by regulatory agencies like the FDA and EPA. They are both looking more closely at this issue, thanks to the advocacy of scientists and others.”

It’s also worth noting that perhaps not all products present the same risks. “It is presumably more likely that triclosan in a water-solubilizable form [soft-soaps for example] would be more risky than that which has been incorporated into something like a mattress or sneakers,” suggests Levy, who notes that even with these products, the fate of antibacterials is unknown.

So where does that leave us? According to Dr. Bernadette Albanese, a public health expert, “If people spent as much time washing their hands, as they do reading the labels of this stuff, we’d all be better off. Putting antibacterial in soap, towelettes, band-aids is mostly useless. The message should be proper and frequent hand washing, use plain (liquid) soap and paper towels. That is the message the public needs to hear.”

Although I’m not sure I’m ready to give up the microban treated Tevas (have you smelled a well-worn pair of Tevas?) I’ll definitely be reading my consumer products labels more carefully.

Plutonium, By the Way.....

I had been working on a project about the development of nuclear power plants in this country and through a list-serve of scientists and engineers found a few who were willing to educate me on the early days of nuclear power. They’d spent most of their lives working either for the industry or for government regulatory agencies, and had a lot to say about the early days. This provided some pretty interesting reading. It was one of my last questions however, about worker health, which clearly revealed the bias of one respondent.

“By the way,” he wrote, “plutonium is not toxic when eaten. You can eat it with a spoon if you want to.” To his credit he did concede that if you happen to inhale plutonium, there is a long-term risk of cancer, “just like naturally occurring polonium in tobacco smoke.”

He’s right of course. You could eat plutonium if you wanted to. You could also eat dioxin or arsenic if you wanted. But why would you?

Plutonium, like some forms of strontium, uranium and the now famous polonium-210 is a radioactive metal or element, although plutonium and radioactive strontium differ from uranium in that they do not occur naturally in our environment (for the most part) but are by-products of our “tinkering” with natural elements. Human activities like uranium mining, nuclear weapons production and testing, and nuclear energy production, are the primary human activities which have lead to environmental releases of plutonium, radioactive strontium, and other radioactive elements.

What sets apart the radioactive elements from the non-radioactive elements is their lack of stability. They can disintegrate spontaneously, sometimes even changing into other elements over time. Uranium, for example, will eventually decay into lead (although it may take billions of years.)

Generally speaking, elements are defined by what is in their nucleus. The nucleus of any atom consists of protons (positive elements), neutrons (neutral elements) and electrons (negative elements). While the chemical properties of an element are primarily dependent on the number of protons in the nucleus, the radioactive properties generally depend on the number of neutrons, and the balance among the protons, neutrons and electrons. An element can have several different stable forms, or forms in which the number of protons remains the same (thereby imparting the chemical properties), yet the number of neutrons might vary. Water, for example consists of two hydrogen atoms and one oxygen atom. Most often, the hydrogen in water contains just one proton and one neutron in its nucleus. This form of hydrogen is stable and does not undergo radioactive decay. But some hydrogen atoms exist that have two or even three neutrons. Those with two are called deuterium and those with three are referred to as tritium. Both deuterium and tritium can combine with oxygen forming heavy water which, for the most part, behaves chemically just like normal water. Deuterium atoms are stable. Tritium atoms however are not stable and at some point in time they will disintegrate, eventually leading to the production of helium (although in a much shorter period of time than it takes uranium to decay to lead - something in the order of decades rather than billions of years).

When atomic disintegration occurs radiation is released and depending on the element, may occur as alpha particles, beta particles or gamma rays. Although each one of these radioactive emissions has their own characteristics (see box), all three types are known as ionizing radiation, a powerful form of radiation capable of stripping electrons from other atoms and molecules (causing them to become either unstable or reactive) and breaking chemical bonds. The displaced electrons become free energetic electrons, and in turn are capable of imparting their energy to electrons of other molecules, either exciting them or knocking them out, continuing the process of bond breaking, excitation, and ionization.

In the body, the making and breaking of the chemical bonds between atoms is a highly coordinated process, normal and essential to life, and the “unscheduled” breaking of chemical bonds can cause cell death, permanent cell damage, or damage to the cell’s DNA.

Human DNA is contained within the 46 chromosomes (making up 23 pairs) that carry our genetic code. Replication of these chromosomes during cell division is a critical process, requiring an immense number of complex biochemical interactions, which involve copying and construction of identical chromosomal pairs that are split off into the newly divided cell. Since integrity of the genetic material is essential to life, there are biochemical systems involved in maintaining chromosomes during division, including mechanisms by which errors may be repaired.

As discussed above, ionizing radiation results in highly energized electrons that are capable of breaking any chemical bond in the body. Likewise, the track of an energized electron is capable of breaking chromosomal bonds, thereby breaking off pieces of the chromosome. Once a break occurs, depending on conditions within the cell and location of the break, the broken pieces may rejoin the chromosome, leaving little or no evidence of damage; the broken piece may remain separate, becoming a chromosomal deletion; or the deleted piece may continue to copy itself, as will the chromosome that is now lacking a portion of genetic information. It is generally agreed that the critical genetic damage from ionizing radiation is most likely the result of chromosome breaks, although other types of genetic damage can occur as well.

If the genetic damage becomes permanant, or “fixed”, and begins to propagate within the cell, the change can lead to the development of cancer, or to mutations that may be either genetic (capable of being passed on to offspring) or teratogenic (impacting only the exposed fetus) in nature.

So, when an element like plutonium disintegrates, it releases alpha particles and though these particles don’t travel vary far, once inside the body (say, from ingestion or inhalation), they are capable of interacting with, and potentially harming any bodily tissue along their path.

In other words, wherever the plutonium ends up, be it in the stomach, or the liver, or the bones, where it’s most likely to travel once it leaves the stomach, it has the potential to emit alpha particles, and cause tissue damage for as long as it remains in the tissue, which in the case of plutonium can be decades.

There is a great deal of information on the health impacts of radiation available on the web. Here are a just few sites that may be of interest if you wish to learn more:

The Institute for Energy and Environmental Research:


And, if you really want to read the details there is the National Research Council’s latest report on “Health Risks from Exposure to Low Levels of Ionizing Radiation,” which is available online (and for purchase) at


Radiation Type


Distance traveled in air

Health threat from external exposure (penetration)

Health hreat from internal exposure

Emitted by:

Alpha (a)

2 protons, 2 neutrons




Plutonium-236; uranium-238, radium-226

Beta (b)





Strontium-90; tritium, Iodine 131; Cesium 137

Gamma (g)

Photon (electromagnetic radiation)

Thousands of meters



Cobalt-60; Cesium-137

Are all the frogs really dying?

Scientists agree that frog and toad populations in the United States and around the world are in decline. Of about 100 different species in the U.S., twenty-two are listed as threatened or endangered. Worldwide, there are thousands of species with hundreds nearing extinction. Yikes!

But there is hope. If scientists can figure out why so many species are threatened, then maybe we can save all those peepers and croakers from singing their last tune.

Frogs and toads are amphibians, spending part of their lifecycle in the water, and part on land. And, unlike most landlubbers, they have very thin permeable skin which absorbs both water and air. Because of this feature frogs and toads are good indicators of changes in the earth’s environments and for this reason are considered the global version of the “canary in the coal mine,” only this coal mine is the planet earth! So far scientists have identified several possible changes that could impact survival of frogs: global warming, pollution, disease, and habitat destruction.

From eggs, through the tadpole stage, frogs are surrounded by water. These early life stages are considered the most sensitive to environmental change. Recent studies for example, have found that the most commonly used weed killer in the U.S., atrazine, wreaks havoc on the developing sex organs in male frogs, so much so that some male frogs end up with both male and female organs.

Additionally, parasitic infections in developing frogs are thought to be responsible for formation of excess limbs, and fungal infections in adults have been linked to population declines in other parts of the world. Scientists think that other factors such as global warming, ozone depletion and toxic chemicals may make frogs more vulnerable to infections that otherwise would not have bothered them.

Finally there is wide-spread habitat destruction. As mentioned above frogs and toads require both aquatic and terrestrial habitat, and reduction in either one or both of these habitats could contribute to the decline of frog and toad populations.

But don’t despair! These are not insurmountable problems. Understanding toxicity of pesticides to frogs and toads may lead to greater restrictions on their use (it worked for the Bald Eagle,) and there are currently treaties to prohibit the release of ozone-destroying chemicals. But with over 200,000 acres of land cleared daily (an area equivalent to New York City) habitat destruction seems a thornier issue. So it’s up to all of us, to get on the ball, and help save our amphibious friends.

A good way to begin is to check out the National Wildlife Federations Frog Watch Program at

Thursday, November 30, 2006

Sunscreen Lotions: Do They Block More Than Just Sun?

Sunscreen Lotions: Do They Block More Than Just Sun?

Slip, slop, slap. Sunscreens are a summer staple. When the kids were young, I slathered the stuff all over them. As a toxicologist, I knew better. As a mother, I just wanted the convenience of allowing them a day at the beach, free to play in surf and sand without fear of sunburn.

From my own work, I know that any additional chemicals we add to our bodies and our environment come with some risk. As a mother and a consumer, I want to believe that all those federal protections really work. I want to believe that something that comes in pink bottles with pictures of beach balls and kids splashed across the front of them is safe.

My kids are now nine and twelve. Roughly ten years and countless pink bottles later, I read that those UVA- and UVB-chemical blockers, the active ingredients we look for in our sunblock, can now be categorized as endocrine disruptors, a group of chemicals which includes pesticides, plasticizers, and natural and synthetic hormones. Chemicals that interfere with normal development and reproduction.

Ever since the Federal Food and Drug Administration first approved of sunscreen products for the protection against skin cancer in the 1970’s, the sunscreen industry has thrived, growing into a nearly billion dollar business. During the summer months, young and old alike entrust their skin to the protective qualities of an array of sunblock crèmes and lotions, applying the stuff liberally, several times a day.

The sun’s ultraviolet rays can damage skin in at least two ways. The longer UVA rays that constitute the majority of sun’s ultraviolet light reaching the earth are responsible for “tanning” and penetrate deep into the skin, while the shorter UVB rays penetrate fewer layers of skin, causing “sunburn.” While the UVA rays are blamed for premature ageing of the skin, both rays are capable of causing skin cancers.

Sunscreen filters work by absorbing the sun’s high energy rays and chemically converting that potentially harmful energy into heat and less energetic, less harmful rays. But, it may just be that the chemical structures necessary for absorbing and converting UVA and UVB rays, are also capable of combining with chemical receptors in the body that, under normal circumstances combine only with our natural chemical messengers like estrogens (female hormones) and androgens (male hormones.)

“I first became interested in UV-filters after a colleague reported their presence in human breast milk,” says Margret Schlumpf, from the University of Zurich, who discovered that the majority of sunscreens filters tested are endocrine active in mammals. It turns out that once applied to the skin, some UV-filters are absorbed and distributed throughout the body with some ending up in baby’s milk.

Using a cell-proliferation assay, which measures increased growth in a cultured breast cancer cell-line following exposure to estrogen or estrogen-like chemicals, Schlumpf found that eight out of ten sunscreen-filters tested positive.

“Of the ones we tested, we did not find many UV-filters that were inactive.”

But cell-proliferation assays don;t measure activity in living creatures, and as many scientists will note, activity “in the test-tube,” does not necessarily imply activity in the body.

Estrogen has many different roles in the body, from maintaining normal brain function to essential roles in breast development, puberty and pregnancy. In mammals, estrogen stimulates growth of the uterus, and over the years, scientists have employed uterine growth as a sensitive marker of estrogenic activity in living animals. Using this assay, Schlumpf and her colleagues reported in the journal Toxicology that six out of nine sunscreen filters tested positive for uterine growth in rats. The researchers noted, however, that effective concentrations of sunscreens were well above those we, or our kids are likely to encounter after a weekend in the sun.

As a mother, I was satisfied by this news, that over the years I hadn’t caused inadvertent sex-reversal in either of my children (although sometimes I think delayed puberty might not be such a bad thing,) but I wondered about those federal protections.

Haven’t these products passed a battery of tests before reaching our skin? Why, if these chemicals have been in use for decades, are we just finding out about these endocrine disrupting properties now? Turns out they are tested, but, as “Over-the Counter” drugs, not as rigorously as prescription drugs, or even some pesticides and industrial chemicals.

Although I couldn’t get a straight answer from the FDA when I asked if these chemicals had been tested specifically for endocrine disrupting activity, they did respond that it is suggested, but not required that chemicals such as sunscreen filters be tested for adverse effects on endpoints like fertility and embryo or fetal toxicity. As a toxicologist, I understood this to mean they’ve likely not been tested for the subtleties of endocrine disruption. And these days, it seems the more researchers look, the more they find chemicals capable of endocrine disruption.

In essence we are exposed to mixtures of chemicals, albeit at low concentrations, that may be capable of greater activity when combined. When I asked Dr. Schlumpf if any one sunscreen is likely to have more than one endocrine disrupting or estrogenic chemical (increasing the total amounts of these chemicals to which one might be exposed,) she replied, “Many have more than one UV-filter. Then there are some synthetic perfumes, and other chemicals like pthalates, those chemicals commonly found in cosmetics and plastics (that can also serve as endocrine disruptors.)” And that’s just in one lotion.

Schlumpf isn’t the only researcher concerned about the impacts of sunscreen filters. Karl Fent’s laboratory at the University of Applied Sciences Basil, Switzerland, reported on the estrogenic activity of UV-filters in fish in the January 2006 issue of Toxicological Sciences. When asked why fish, he responded, “We did an earlier study with UV-filters in frogs and wondered about other important aquatic species. Residues of UV-filters are found in fish.”

Ten out of the twenty-three sunscreen filters tested by Fent’s group had estrogenic properties, and three out five tested were active in live-fish, capable of inducing production of egg-yolk protein, a common test for estrogenic activity in egg-laying animals.

Though Fent noted that, “Profound effects occurred at concentrations higher than in the environment so the question of impact on wild fish populations is open.”

This is especially true when one considers that for each complex mixture of endocrine disrupting chemicals in any one brand of sunscreen that washes off our skin while swimming or later, in the shower, there are hundreds if not thousands of other endocrine disrupting chemicals that make their way from our homes and our bodies into the aquatic environment.

Marianne Balmer, another Swiss researcher from the Swiss Federal Research Station, measured quantities of UV-filters in both Swiss lakes and in fish tissues. “For small rivers, wastewater treatment plants were the main source of UV-filters. But, in lakes used for recreational activities, direct imputs, washing off from the skin during bathing, may contribute significantly to the UV-filter load,”

Closer to home, some UV-filters have turned up in coastal waters receiving sewage treatment effluents in New York and in California where researchers reported finding male fish carrying not only sperm but eggs as well, (although they cannot at this time point to any one environmental chemical as the cause). The United States Geological Survey has added sunscreen-filters to their growing list of chemicals detected in our nation’s waters, and they are currently developing methods for detecting UV-filters in sediments.

When asked for thoughts on the application of UV-filters to infants, young children, and/or pregnant women, those considered most sensitive to the impacts of endocrine disrupting chemicals, Dr. Schlumpf replied, “ I wouldn’t advise pregnant women and small kids to put on tons of sunscreen, but I would recommend they protect their skin. Not being in the sun all the time will reduce the amounts of sunscreen used greatly.”

My kids aren’t so small anymore, but now, besides the tube of sunblock, I’ve got a couple of SPF-30 t-shirts tucked away in the beach-bag.