Wednesday, July 30, 2008

Precaution and Triclosan

The other day I was pointed to an article by Cass Sunstein in the Boston Globe online, about the precautionary principle. I agree with Dr. Sunstein that fundamentally the precautionary principle is incoherent as a risk management tool, at least in the way a lot of the “deep green” people view it. All policy choices entail risks of some form; these may be disparate risks that fall differentially across the population, but we risk making irrational decisions if we don’t try to wrestle with them. Some of his examples are pretty dim, but then again he’s writing for the general audience, who is pretty dim when it comes to making decisions where uncertainty is involved.

In most or nearly all cases where risks are being assessed, you’ll be making a decision based on incomplete information. It may not be prudent to allot the time or resources to do the studies to more fully assess a risk before deciding to act on it. Indeed, the call for more study has become a strategy used by some corporations for deferring action on controlling health risks associated with their products, or with chemical substances that their workers are exposed to. It’s effective too, because, like the general audience, nearly all policy makers are genuinely bad dealing with environmental decisions under uncertainty.

There’s a “strong” version of the precautionary principle, which in effect is to take action to stop something that poses a significant risk until you prove it’s safe. That’s a recipe for either precipitous action or inaction, with Dr. Sunstein’s favorite example being invading Iraq. The more reasonable version of the principle suggests that a lack of decisive evidence of harm should not be grounds for not taking action. For example, the 1992 Rio Declaration, setting out principles for sustainable development, states, "Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation" (see Principle 15).

Of course, matters become more difficult to resolve in practice. A good example is antibacterial soaps containing triclosan. Soaps containing triclosan were no more effective than plain soap at preventing infectious illness symptoms and reducing bacterial levels on the hands. Also, several laboratory studies demonstrated evidence of triclosan-adapted cross-resistance to antibiotics among different species of bacteria. The conclusion of a recent review was:

The lack of an additional health benefit associated with the use of triclosan-containing consumer soaps over regular soap, coupled with laboratory data demonstrating a potential risk of selecting for drug resistance, warrants further evaluation by governmental regulators regarding antibacterial product claims and advertising. Further studies of this issue are encouraged.

Triclosan is used extensively in consumer products, including personal care products, textiles, and plastic kitchenware. The triclosan molecule has some structural similarities to phenols, diphenylethers and polychlorinated biphenyls (PCBs). It is widespread in low levels in waterways throughout the U.S., and has the potential for bioaccumulation in the environment. Biological monitoring performed by the CDC in 2003 and 2004 has detected triclosan in 75 percent of the urine samples collected from a representative sample of the U.S. population. In other words, traces of triclosan are detectable in a large number of people. Finally, triclosan was recently screened using mammalian cell lines for endocrine disrupting potential, and yes, there’s a possibility it’s an endocrine disruptor (potentially interfering with cell signaling that occurs in brain, heart and other cells, according to the UC Davis researchers).

Antibacterial soaps and consumer products have been identified as risk factors for antibiotic resistance. Infections from Methicillin-resistant Staphylococcus Aureus (MRSA) are becoming a growing concern for hospitals and healthcare professionals. Recommendations for managing MRSA in the community aren’t calling yet for getting rid of soaps and products containing triclosan. Noone is calling triclosan a threat to human reproduction yet (for example, CERHR isn’t investigating it).

However, it does raise the question of when action is warranted to reduce exposure to triclosan. There’s limited evidence that it isn’t terribly effective as an antibacterial agent in consumer products, and may contribute to antibiotic resistance. It’s widespread in the environment, bioaccumulative, detectable in humans, and now has emerging evidence of subtle adverse effects that might affect future generations. Absolutely nothing conclusive about any of it, but with the currently regulatory framework and political environment, it could involve decades of study and deliberation before a decision is made that widespread use of triclosan poses a risk or not. Then, if the determination is yes, it poses a risk, several more years would be required before it’s out of the product distribution chain.

This seems like a perfect application for the precautionary principle. However, until the precautionary principle develops some intellectual rigor, and possibly a quantitative framework, it’s going to remain a nice idea without a lot of decision-making punch.

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Sunday, July 13, 2008

We Need Biomarkers

As desirable as the idea sounds, we might have to finally admit to ourselves that reducing human exposure to toxic substances by curtailing their use isn’t working. There are a lot of good initiatives out there in green chemistry, and there’s REACH, but these are years in the future before they start having any effects on really reducing human exposure. The time factor bites here; there’s a progression from research initiative and legislation to regulatory programs and enforcement, pilot testing, redesign and startup of new production plants, and distribution of the new toxic-free products through the supply chain – a process that requires many years. Existing products, such as polycarbonate plastic baby bottles or computer cases with polybrominated diphenyl ether (PBDE) fire retardants, may remain in use for many years even after production and sale of them ceases, providing a continuing source of exposure. Once exposure ceases, additional time passes before human body burdens decline; the amount of time depends on the persistence of the substance in the environment and in the human body.

Bisphenol-A is metabolized rapidly in humans, and body burdens should decline quickly, once we get around to removing it from food and beverage containers. However, even with nearly a decade of intensive scientific study, we still haven’t been able to come to a decision of whether or not bisphenol-A poses a threat to human health that warrants its replacement in plastics. PBDEs will be with us for generations, even if we eliminated all of them from all products today, because of their persistence in soil, water and the foodchain. A concerted effort has been made over the past 15 years to reduce dioxin exposures, which has resulted in decreases in body burdens. The question remains as to whether that effort has been sufficient – we still don’t have an accepted assessment of dioxin health risks.

Note this doesn’t mean “giving up” on clean production. Elimination of high-toxicity substances and substitution with lower toxicity materials is always the first choice in reducing human exposures (next in the hierarchy are engineering controls, personal protective equipment and lastly, administrative controls). Adhering to good design philosophy, and attempting to use smaller quantities of lower toxicity materials along with lower amounts of energy, should remain an objective for all types of manufacturing. But at the same time, we shouldn’t kid ourselves that clean production is going to have a measurable effect on human exposure to toxic substances anytime in the near future. It would be helpful if we had a robust set of biomarkers of toxicity in humans.

Regardless of where you fall on the “yes they do”/”no they don’t” continuum about environmental chemicals causing cancer, you have to admit that the National Academy of Sciences nailed the problem when it said last year:

Many cancer patients are diagnosed at a stage in which the cancer is too far advanced to be cured, and most cancer treatments are effective in only a minority of patients undergoing therapy. Thus, there is tremendous opportunity to improve the outcome for people with cancer by enhancing detection and treatment approaches. Biomarkers will be instrumental in making that transition.

Even further, the NAS’s report on cancer biomarkers says, “. . .recharacterization of disease in pathophysiological terms via the use of biomarkers is the key to the future of medicine.” Wow. If true, biomarkers taking off could really move the “war on cancer” out of the slash and burn (i.e. surgery and chemo/rad) mentality to something more sublime, less painful and scary and probably more effective in protecting health and improving quality of life.

Postscript: A companion post is in preparation that talks more about what are biomarkers and what we can do with them, beyond saying they are early indicators of processes or events in the body that might in the future lead to disease.

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Sunday, July 06, 2008

Wrong Answer

A few days back I was driving around running an errand and happened to catch on the radio “MarketPlace”, that annoyingly smug business program carried on NPR stations. I try not to listen to NPR any more, but it’s one of those things that’s hard to stop once you’ve started, like cigarettes or heroin. Anyway, they carried a story about energy independence blah blah blah, and how someone was trying to commercialize plasma gasification as a waste to energy technology. Plasma gasification uses high temperatures to convert organic materials into “syngas”, or a gas stream composed mostly of carbon monoxide and hydrogen. These two substances then can be catalytically rearranged to form methane, hydrogen, and hydrocarbon fuels. It's been tried as a means of biomass conversion in a few places.

There was a hint of conspiracy theory about why this technology just isn’t all over the place, making truckloads of money for its proponents.

You know, we would be taking away a large business for the landfill people and the incinerators, so waste company do not want to see this technology come out. On the other hand, if we produce power, we will be infringing on the coal business and fossil fuel burning business.

I guess the energy consumption and expense involved have little to do with it. The other point that was brought up in the article as a reason we “need” this technology is that we’re running out of landfill space. . . .

The “running out of landfill space” argument is always a sign that you’re talking to someone who doesn’t really know much about environmental issues. We’re not running out of landfill space these days, so much as we’re running out of political will to site landfills where they are needed. Landfills also are a sign of mismanaged resources. For example, a significant chunk of the copper from the entire lithosphere is in landfills, a fact coupled with rising demand in China, which helps explain why thieves are starting to strip copper fittings out of abandoned forclosed homes. This article points to more examples of metals whose stocks may be approaching exhaustion. I found it from a Daily Kos diary “Peak Metal”, which has a nice analysis of the problem, but then mars it by indulging in liberal handwringing about how hard metals reclamation will be, and engaging in NIMBY-ism about how you don’t want a landfill mine as a neighbor (knee-jerk NIMBY thinking being another sign you’re talking to someone who doesn’t really know much about environmental issues).

So, we don’t need to be melting garbage to make fuel or electricity – we have other ways of getting those things. However, we are probably past the point where we need to start reclaiming and reusing the crap we’ve been tossing away so blithely. Noone yet is talking seriously yet about landfill mining, but if we’re arresting people for stealing copper, digging up landfills for it can be only a matter of time.

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