Making Lists: Dr. Cal's thoughts on priortizing chemicals

Guest blogger, Dr. Cal Baier-Anderson, a toxicologist at the University of Maryland, Baltimore; and Environmental Defense, adds her own thoughts about prioritizing chemicals (also check out the list created by J. Lowe from Impact Analysis in the comments section of Fav Five.)

A few years ago at a professional meeting I participated in a panel on the chemical perchlorate, which was receiving a lot of attention as an emerging drinking water contaminant. Perchlorate, an oxidizing agent that is used in rocket fuel, can block the uptake of iodide in the thyroid. One member of the audience suggested that focusing attention on perchlorate was a waste of time and money, that there are other chemicals that are more important. Make a list, I challenged the group; professional organizations and industry should step up to the plate and identify the top 10 chemicals of concern, from an industry perspective. It is certainly not an easy task, as Emily pointed out, many different lists can be made, depending on what features are most important.

With tens of thousands of chemicals in commerce, chemical prioritization is a hot topic. The traditional risk assessment process focusing on one chemical at a time requires a lot of data collection: the identification of the most important hazard endpoints (a prioritization process in and of itself); determination of dose-response for the priority endpoint, the characterization of exposure; and the assessment of risks. Chemical prioritization can be based on hazard, it can be based on likelihood of exposure, or it could be based on risk, incorporating both hazard and exposure. Many environmental groups argue that there is so much uncertainty in the risk assessment process that it is better to focus on hazard, emphasizing carcinogens, mutagens, reproductive toxicants, and endocrine disruptors. This has lead to the creation of lists, such as California’s Proposition 65 list of carcinogens, mutagens and reproductive toxicants (CMR), which requires that products containing a chemical on this label their products with a special notice.

Chemicals that can be classified as persistent, bioaccumulative and toxic (PBT) are also considered to be high priority chemicals. EPA initially devised a list of PBT chemicals, but then developed a computer program that evaluates individual chemicals to score them as to PBT properties. Persistence and bioaccumulation are determined by basic chemical properties, whereas toxicity is based on aquatic toxicity data.

With public attention focused on chemicals in consumer products, many companies are critically evaluating their products’ ingredients to determine if they are made with chemicals of concern. But how can we define chemicals of concern? Based on hazard, or based on risk? Some companies have developed their own restricted substances list that contains chemicals that the companies believe to pose some unacceptable risk to their workers and/or consumers. REI has a list, but a simple Google search of “restricted substance list” will uncover many more.

At the recent SOT meeting in Seattle, there was a session on hazard vs. risk-based approaches. Many state governments and large companies are defaulting to hazard-based approaches as a simpler approach to removing chemicals of concern from consumer products. Several prominent toxicologists opined that focusing on hazard without considering exposure will result in time and money wasted on chemicals posing very little risk. But as my colleague noted during the discussion, there are many folks in the environmental community that are wary of our capacity to predict exposure, citing numerous examples where it was initially predicted that there would be no exposure, and the experts were wrong: PCBs, Bisphenol A, phthalates, PFOA, PBDEs…If we can’t correctly predict exposure, then confidence in the risk assessment plummets, shifting focus to hazard.

A new approach is being promoted by some very smart people: alternatives assessment. Rather than making simple restricted substances lists, focus on what are the alternatives and compare using a suite of criteria. These assessments can be used to drive continual improvement in materials safety – protecting workers, the environment and consumers. Makes sense to me!

What’s in Your Fav Five? Five top contaminants

I’d been blabbing away for the past hour or so about chemical contaminants, imparting my imperfect knowledge upon my seven brilliant college students.

“So, what do you think are the five most important contaminants?” asked Beth, my student who has been investigating atrazine, one of the most ubiquitous pesticides in this country.

I was speechless. “Um..” I wavered, “well….” I pondered, before finally copping-out with “that’s a really good question.”

“I guess that’ll be my assignment,” I grimaced, “but I’m not sure I’d be able to come up with just one list.” Although it seemed a fair if not daunting assignment, since I’d been asking them to stretch their brains all semester, I’m guessing if you asked ten toxicologists for their “Fav-Five” they’d come up with at least twenty different lists.

As with anything in toxicology, there are some basic questions about exposure, toxicity, how the stuff behaves in the environment, and who’s most at greatest risk? For example, we might use some pretty nasty stuff to clean our ovens, paint our toenails or kill rats but we might not expose ourselves to concentrations that are of concern (though that might be debatable), unless we drink them.

Then there’s toxicity. Does it cause cancer? Impair reproduction? Contribute to the development of asthma? Which is worse? Or maybe it’s more insidious, as one of my students, Liz, revealed about a group of fragrances, used in more consumer products that I can name, called synthetic musks. Some of these compounds impair the ability of our cells to spit out foreign chemicals. Finally, there’s the question of how the chemical behaves in the environment, and in us. Does it accumulate? Do we metabolize it? Does it seep into water? Is it spewed into the air? And this is just considering human toxicity. Finally there’s the ‘at risk’ question. Are we talking most problematic for humans? The Environment? Wildlife?

My brain was off in all directions. There are just too many variables. Even David Letterman hasn’t attempted at top-ten list for chemical contaminants I checked.

But I already copped-out once. I couldn’t do it again. So I did some academic soul-searching (A.K.A: A Google Search).

Maybe there are some existing lists that hordes of experts, policy makers and regulators have already developed? But no such luck (although please correct me if I’m wrong. I’d love to see one.) Then I dared write to representatives from USGS and EPA’s Office of Water, but got no response other than a boiler plate answer from the EPA's press office assuring me that in addition to protecting us from acute problems like pathogens, "EPA is concerned that water systems protect their sources of drinking water, address replacement of aging infrastructure, have properly trained operators, and charge sufficient rates to ensure that they have the revenue needed to provide access to safe drinking water."

So for better or worse it seems I’m on my own (with help from the universe of information available on the web – and these are in no particular order – they are about as random as my selection process,) though I’d love to see a poll of those in various fields to see what they’d come up with, here goes – not in any particular order:

1) Arsenic is linked to many different types of cancer, and occurs naturally in soil and water (and may occur in drinking water). It's a chemical once used widely as a pesticide. As a result it may be found in the neighborhood playground (arsenic is one of a triumvirate of metals in CCA or chromated copper arsenate,) or contaminate the soil of old fruit orchards (and elsewhere) thanks to its effectiveness as a pesticide. In terms of large scale environmental release, mining industries – like the Newmont Mining Corporation, in Nevada which describes itself as one of the leading gold companies in the world - may be most important. According to Scorecard a site originally created by Environmental Defense (and now "owned" by Green Media) that digests and synthesizes EPA’s Toxic Resource Inventory into a more readable format, arsenic is the number one cancer concern, and Newmont releases almost 300 millions pounds of arsenic a year into the surrounding environment.

Arsenic also tops the Agency for Toxic Substances Disease Registry Top 20 List which is based on contaminants most commonly found at National Priority List or Superfund sites and which are considered most important in terms of potential for exposure and potential for causing adverse health effects.

Finally, in 2002, the EPA dropped the drinking water standard from 50 part-per-billion (ppb) down to 10 ppb, after considering even lower standards of 3 and 5 ppb.

2) Lead. This is not only important as a neurotoxic contaminant now because it exists in old house paint and other paint (e.g. on old peeling highway bridges), courtesy of the lead industry who once encouraged Americans to paint their houses with white lead, and advertised, yes actually advertised that “Lead Takes Part in Many Games,” (see Deceit and Denial for some fascinating reading,) but it’s also in our water having been used for pipes and solder. The EPA estimates that twenty percent of human lead exposure is the result of contaminated drinking water. Lead also tops NRDC’s Scorecard for number one, non-carcinogenic contaminant, this time thanks in part to Red Dog Ops in Alaska, another mining company.

Several years back, as a pregnant mother of a toddler, I dutifully tested the window sills of our new 1860’s home for lead paint – when the hardware store lead-test stick turned a shade of hot-pink I hadn’t seen since the psychedelic ‘70s. I immediately (and maybe not so wisely) purchased some gel non-toxic stripper and scraped away. Sometimes we do dumb things. And sometimes we just don’t learn. Maybe we will this time around.

Here’s a little ditty I found on EPA’s site:

Hence gout and stone afflict the human race;
Hence lazy jaundice with her saffron face;
Palsy, with shaking head and tott'ring knees.
And bloated dropsy, the staunch sot's disease;
Consumption, pale, with keen but hollow eye,
And sharpened feature, shew'd that death was nigh.
The feeble offspring curse their crazy sires,
And, tainted from his birth, the youth expires.
(Description of lead poisoning by an anonymous Roman hermit,
Translated by Humelbergius Secundus, 1829)

3) Priority Air Pollutants. Air is not my field, but no top-five list can be complete without at least a few air pollutants. These include particulate matter - released by power plants, motor vehicles, (especially older diesel vehicles), and some factories; ground-level ozone (primarily from motor vehicles and industry), carbon monoxide (from burning fossil fuel), sulfur oxides (fuel again, particularly coal burning plants), nitrogen oxides (yup, burning fuel again) and finally lead (again – so now you see it’s a double assault.)

We’ve all heard how asthma rates are going up. At least a few of those pollutants listed above aggravate asthma, and are known to cause or aggravate other respiratory conditions (for a historical perspective on the killing smog of Donora Pennsylvania, When Smoke Ran Like Water is a sobering read)

Although thanks to the Clean Air Act, smoke no longer runs like water, it’s still a pervasive pollutant, as anyone with a respiratory condition will tell you. As a parent who watched her asthmatic toddler’s every breath, and then watched as he bounced off the walls following massive doses of Ventolin (he’s thankfully grown out of it), I cannot imagine living in fear of the air. But people do, every day, and it’s criminal. Unfortunately, unlike water, until the sources clean up their act, there is no choice when faced with contaminated air (except perhaps, to visit one of those oxygen bars.)

4) Trichloroethylene, the “miracle” solvent of the twentieth century. I don’t know of too many contaminants that have their own blog, except for TCE (there’s also a very active TCE list serve run by Lenny Siegel, director for Center for Public Environmental Oversight). Though it may or may not reflect the importance of this developmental immuno - , neuro – (basically you name it) toxic and potentially carcinogenic contaminant, it does reveal the importance of this chemical. According to the EPA, TCE is present in 60% of their National Priority (NPL) or Superfund sites around the country, not to mention all the tens of thousands non-NPL sites contaminated with TCE as a result of past industrial, military, small business, or legal and illegal dumping. TCE not only contaminates water – including drinking water, but, depending on the depth of the water table and soil conditions, TCE vapors from contaminated ground water can and have intruded into homes, businesses and schools. Several years back, a class of mine worked with residents in North Adams, MA – a town where seventeen houses were bought-out and razed because of concerns about TCE vapor intrusion.

5) Bisphenol-A. Actually, I don’t know that anyone might consider this one a top-five, though it’s certainly among the top-five in “Buzz.” Bisphenol A is one of those seemingly all too-common estrogenic plasticizers. As we’ve all heard by now, this is the stuff that leaches from polycarbonate bottles – including those colorful Nalgene bottles that college students carry around (to make a statement about their environmental mindfulness) baby bottles, metal can linings, and even tooth sealants. Way back when, in the dark ages of 1993, when the realization that very small amounts of chemicals could really tweak developing reproductive systems was just dawning, the EPA’s Integrated Risk Information System (IRIS) stated, “The developmental toxicity of bisphenol A has been adequately investigated. Confidence in the RfD, therefore, is high.” Consequently the EPA set the “Reference Dose,” an amount considered as safe, at 50 parts per billion per day. Recent studies now suggest concentrations nearing this reference dose may cause reproductive and developmental toxicity. Bisphenol A now contaminates rivers, streams, with unknown impacts on wildlife, and because of its use in consumer products, its in us as well, at concentrations nearing the EPA reference dose.

Phew. That about does it for me, I now submit to class for grading. Comments, corrections, additions and subtractions are welcome.

EU to the Rescue? Regulating Toxic Chemicals

Throughout my professional life, I have, for the most part buried my head in research. That’s what it’s all about - the science - right? Wrong. Not when it comes to toxic chemicals. Back when I was in graduate school, there were some hints that other things, like regulation and risk assessment were important – but I couldn’t be bothered. Even as Sheila Jasanoff, who boggled me with her intelligence and eloquence, led us graduate students through the morass of legalese in her Toxic Torts class, I just didn’t get it. Why laws were written so unintelligibly I could never understand, except maybe to help employ more lawyers.

So twenty years later – maybe even to the semester that I earned the only “C” in my post-secondary career (well – I also pulled off a C in History of the World a well known “gut,” freshman year of college), I am struggling to understand why our country’s Toxic Substances Control Act, the legislation designed to protect us from harmful effects of toxics does not; and why Europe’s new chemical control policy promises so much more.

Thankfully I’m not the only one trying to figure this out. This summer the General Accountability Office or GAO released a report comparing TSCA with Europe’s new Registration, Evaluation, and Authorization of Chemicals (REACH) legislation. Noting one primary difference between the two, the GAO states:

“TSCA places the burden of proof on EPA to demonstrate that a chemical poses a risk to human health or the environment before EPA can regulate its production or use, while REACH generally places a burden on chemical companies to ensure that chemicals do not pose such risks …….” (emphasis added)

You don’t have to be a toxicologist to know how difficult it is to determine that any one particular chemical poses a risk, you just have to read the papers. He says this, she says that, and meanwhile, polybrominated fire-retardants contaminate the dust in our homes, bisphenol-A leaches from baby bottles, and we’re wondering how the gasoline additive MTBE, which now contaminates groundwater across the country could ever have been allowed. But now the EU is requesting that industry take the lead ensuring (as best they can) that a chemical poses little risk to human health and the environment before setting it loose.

Then there are the tens of thousands of chemicals that were on the market prior to the 1980 enactment of TSCA. Unless there was reason for suspicion, those were grandfathered into chemical complacency. And into our food, clothing, air and water.

Unlike TSCA, REACH does not distinguish between new chemicals or old chemicals, according to a recent article in Environmental Health Perspectives REACH will require safety and exposure data on something like 30,000 chemicals currently sold in Europe. Those chemicals that are “carcinogenic, mutagenic, persistent or bioaccumulative or toxic to reproduction” will receive special attention. I just hope the EU has armies of toxicologists lined up to review this stuff!

Many times I’ve harped on how we seem to make the same mistakes over and over again. But it seems the EU has finally looked back before moving forward. When in class, I try to make it clear that being toxic isn’t enough to raise the reputation of a chemical to celebrity status. Exposure matters. How and how much we are exposed to certain chemicals is key. Sometimes exposure takes us by surprise. Who knew that polybrominated fire-retardents would shake free from their products (although one would think that their similarity to PCBs and dioxins might have raised some concern early on about their tendency to bioaccumulate), or that bisphenol-A would leach into water and food to the extent that it does, or that MBTE would wend its way around soil particles into our water, leaving other fuel components behind to be degraded? To address exposure – the EU proposes to consider all uses of a chemical – and to inform all “downstream uses,” clothing, cosmetic, packaging manufacturers for example, of not only the chemical’s properties but also how it behaves in humans and in the environment.

This kind of information, according to Joel Tickner, from the Lowell Center for Sustainable Development, (as reported by EHP), may drive innovation towards less toxic, safer products. According to EHP, “[Tickner] says there is a clear interest of downstream users of chemicals who want the functionality of the chemical but not their toxicity. Companies in sectors such as health care, footwear, electronics, and cleaning chemicals have already started to demand these products from suppliers.”

Amen. And with some trickle down – U.S. companies wishing to supply E.U. with chemicals will have to comply with REACH – there’s hope that we can clean up our act here at home.