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Tag: risk assessment

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It’s Time to Move Beyond Risk Assessment

Risk assessment is the standard method for evaluating exposure to toxic chemicals, despite the fact that it’s nearly impossible to do a risk assessment that is objective and accurate. There are just too many hard-to-measure factors affecting the chance that any one chemical will harm us and if so, how and to what extent, and too many ways for personal bias to change the results. For example, there’s been a long argument about whether arsenic causes cancer. We do know that it’s poisonous. It probably does cause cancer, but many people seem to be immune. So we’re not sure how many cases might occur, and what amount of arsenic might cause cancer. Also, it doesn’t seem to cause cancer in animals, so there’s no way to put the information together. When there are information gaps, the only thing we can do is build-in an extra safely factor, by making the “allowable” level a certain amount less than what we think the “safe” level is. But is that really the answer?

The public wants greater protection from exposure to toxic chemicals than provided by the traditional quantitative risk assessment approach which has many limitations and uncertainties. Instead, support has grown for use of a precautionary approach that promotes (1) preventive action, (2) democratic and transparent decision-making with the broadest possible public participation, and (3) a shifting of the questions being asked (e.g., instead of asking what level of risk is acceptable, asking how much risk can be avoided; what is the need; why is it needed; who benefits and who is harmed; and what are the alternatives?) as well as the presumptions used in decision-making (e.g., shifting the burden of proof to the proponents of potentially harmful activities, and placing public health above other considerations).

In its 2009 report, Science and Decisions, the National Resource Council (NRC) of the National Academies acknowledged that risk assessment is “at a crossroads” facing “a number of substantial challenges”, that “its credibility is being challenged”, and that the “regulatory risk assessment process is bogged down”.  The report made a number of recommendations that focused on improving the methodology of risk assessments (e.g., thorough evaluation of uncertainties and variability, unified dose-response approach to cancer and non-cancer endpoints, broadening the assessment of cumulative and interacting health risks and stressors), and improving the relevance or utility of risk assessments for decision-making (e.g., involving all stakeholders at the earliest stage of the planning, design and scoping of the risk assessment, and increasing the transparency of the assessment methods and process).

The NRC recommended two major shifts: (1) “that risk assessment should be viewed as a method for evaluating the relative merits of various options for managing risk”, with the risk management questions being “clearly posed, through careful evaluation of the options available to manage environmental problems at hand,” casting light on “a wider range of decision options than has traditionally been the case”; and (2) aligning closely the technical analysis with the problem at hand so that the risk assessment will be relevant to the needs of the decision-makers and stakeholders who are addressing the problem (e.g., a “one size fits all” approach to risk assessment will not be appropriate for such very different problems as regulating a chemical and deciding on a site remediation approach).

These recommendations are now more than 5 years old, and there’s little evidence that government is adopting these recommendations. Doing so should improve the ability to interpret hazards, contamination levels and population exposures, dose-response relationships, and cumulative risks (exposures from multiple pathways, complex mixtures, multiple stressors, and factors affecting vulnerability), as well as the evaluation of a wide range of alternative options (e.g., inherently safer technologies, alternative ways to achieve the same goal, etc.). It could also provide a way to integrate the risk assessment tool within a broader precautionary approach that seeks to reduce or avoid exposures to toxic chemicals, which the public is actively calling for. It’s time to stop accepting risk assessment as the best we can do to evaluate risks and adopt more a holistic approach to protecting public health and the environment.


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Staying Safe (Probably): Risk, Hazard and Chemical Regulation

‘Risk’ and ‘hazard.’

These two words are often used interchangeably, but they have distinct meanings in the context of chemical safety assessment. When we say a particular chemical is ‘hazardous,’ we are noting its mere potential to cause negative health or environmental effects. On the other hand, ‘risk’ describes the probability that these negative effects will actually occur under specific circumstances. In order to generate a measurable risk, some exposure to the hazard in question must occur.


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Both a hazard and an exposure are necessary for a risk to exist.


If you have followed my last several posts, you’ve probably caught on to the idea that attempting to declare a chemical ‘safe’ or ‘unsafe’ is an exercise in futility. To comprehensively determine risk, we must know not only the detailed structure and function of a chemical, but also understand the intricacies of its interactions with the environment and the human body. Current chemical regulation in the United States operates within a risk-based framework. We establish standards and criteria for acceptable levels of hazardous compounds in products, in the environment and in our bodies; we enact bans and restrictions on chemicals in order to limit our exposures. These regulations are the product of risk assessments, which report not only the hazardous properties of chemicals but also the likelihood of human exposure.

My recent post on BPA illustrates the complexity of risk assessment. Though BPA has demonstrated hazardous potential, the levels to which humans are exposed to the compound, and therefore the actual risks of its use, are uncertain. Exposure may seem like a simple factor to evaluate, but our understanding of exposure is continually evolving, particularly with consideration for the special vulnerability of developing babies and children.  The ban on BPA in baby bottles reflects this emerging awareness of long-term effects of chemical exposures. However, the replacement of BPA with BPS illustrates the shortcomings of an approach that controls risk by limiting exposure to specific high-profile hazardous compounds.

The replacement of BPA, a known hazard, with BPS – an untested and unregulated compound with a nearly identical structure – may be considered an example of what scientists and regulators refer to as “regrettable substitution.” Regrettable substitution occurs when we eliminate one hazardous chemical from consumer products, only to replace it with a similar or even more hazardous alternative. Our risk-based chemical regulation enables us to remove demonstrably dangerous chemicals from consumer products, but also leaves profound loopholes for new chemicals, untested and unregulated, to enter the market in their stead, as long as risk assessments have not proven them dangerous. In a 2010 post on his Environmental Defense Fund blog, Dr. Richard Denison refers to this process as playing “whack-a-mole” with chemicals. No sooner have we knocked one hazardous chemical back into its hole, than a replacement rears its likely-hazardous head…until we generate evidence of its actual risk and seek to replace it with another unknown quantity.

Is this game of “whack-a-chemical” inevitable, or do more precautionary approaches exist? In Europe, regulators are striving for a balance between risk assessment and the more protective approach of hazard classification. While risk assessment relies on scientific studies to determine the risks of chemicals under different exposure scenarios, hazard classification groups chemicals based on their inherent hazard potential. It is this potential to cause harm that guides regulation, not demonstrated adverse effects.  A hazard classification regulatory scheme might have prevented BPS from entering the market, since its structural similarities to BPA make it a likely health hazard.

Hazard classification is essentially a more precautionary approach to chemical regulations. And when we operate in a framework of precaution rather than risk, the regulatory question itself changes. “A precautionary approach asks how much harm can be avoided rather than asking how much is acceptable,” write Dr. Ted Schettler and coauthors in a 2002 essay on the role of the Precautionary Principle in regulation and policymaking.

How can we better incorporate the Precautionary Principle into the chemical regulation process in the US? This question has been at the epicenter of the debate on reforming the Toxic Substances Control Act (TSCA), which I will cover next time on Backyard Talk.

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For BPA, Does the Dose Make the Poison?

For those who keep up with environmental health research and chemical regulations, it is no surprise to come across conflicting reports on the safety or risk of various compounds. This week, in the case of the compound bisphenol A (BPA), these conflicting reports happened to emerge almost simultaneously. On January 21st, the European Food Safety Authority declared that BPA “poses no health risk to consumers of any age group…at current exposure levels.” The next day, a study published in the journal PLoS Genetics showed that even low and short-term exposures to BPA and other hormone-mimicking compounds could alter stem cells and lead to lower sperm counts.

BPA is a common ingredient in plastics used for food and drink containers. Its hormone-like properties allow it to disrupt the endocrine system, with potential health effects ranging from reproductive issues to cancer. Though BPA has been banned in baby bottles in the U.S., and BPA-free products have become widely available since concerns about the compound were first raised in 2008, it remains in products from water bottles to the inside coatings of cans.

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David McNew via Getty Images

‘The dose makes the poison’ is a well-known adage in toxicology, implying that even hazardous chemicals can be harmless at low enough concentrations. However, decades of research have shown this to be an overly simplistic way of analyzing toxic exposures.  Dr. Theo Colborn, who passed away on December 14th, 2014, was a pioneering researcher in the field of endocrine disruption and a tireless advocate for precautionary chemical regulation. Her research on endocrine disruption demonstrated that even very low concentrations of harmful chemicals could result in changes to the reproductive system, particularly in developing babies and children who have less of a tolerance for exposure than adults. She also demonstrated that not all effects of toxic chemicals are immediately apparent, but can occur decades and even generations later.

The study published last week focused on both questions of concentration and timing. The researchers tested estrogenic compounds including BPA on mice, and found that they alter the stem cells, or undifferentiated cells, which are responsible for sperm production later in life. Patricia Hunt, the researcher who led the study, told Environmental Health News that exposure to even low doses of estrogens “is not simply affecting sperm being produced now, but impacting the stem cell population, and that will affect sperm produced throughout the lifetime.”

Uncertainties remain in the wake of this study. For instance, the researchers are still investigating whether the changes observed can cross generations, or whether the same changes can occur in human reproductive stem cells. The EFSA also recognized uncertainties in non-dietary sources of BPA, and they are still conducting long-term studies in rats. While scientists and regulators continue to chase answers, this past week shines a spotlight on the complicated realm of environmental health risk assessment, and shows the continued relevance of Dr. Theo Colborn’s work and legacy. Dose is indeed important in making a poison, but so is timing of exposure, and time itself in revealing the chronic and transgenerational effects of chemicals.

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