Hazardous Chemicals: Risks, Decision-making and Transparency

Professor George Gray of the Department of Environmental and Occupational Health has a clear goal for his work: Help people make better decisions about exposures that affect health. As a former Environmental Protection Agency (EPA) official, current president of the Society for Risk Analysis, and a member of numerous advisory boards, he often helps organizations and government agencies consider the health risks of various hazards, from foodborne diseases to industrial chemicals.

“There’s a great interest now in ‘green chemistry,’ and initiatives to find chemicals that are safer in products or processes,” says Gray. “But it’s rarely an issue of one chemical being safer than another in absolute terms – it’s usually a case of tradeoffs. You might reduce risks for end users, but increase them for workers, or people who live near the manufacturing facility, or people who are doing demolition work or living near a landfill or incinerator.” It’s important to accurately assess the risks of alternative chemicals and consider the entire life cycle of a product, Gray notes.

Gray, a toxicologist by training, was executive director of the Harvard Center for Risk Analysis and a member of the faculty at the Harvard School of Public Health for many years before being appointed to head the EPA’s Office of Research and Development. “Having served at EPA, I know how important it is for decision-makers in both the public and private sector to have good information about risks, and I also know the frustration people feel at the sometimes slow pace of the U.S. regulatory risk assessment process,” Gray says. He joined the GW faculty in 2010 and accepted the directorship of SPHHS’s Center for Risk Science and Public Health with the goal of advancing better, more efficient decision-making about risks.

Faster information for risk assessments

In a commentary in the journal Nature, Gray and co-author Joshua T. Cohen of Tufts Medical Center use the example of dry-cleaning chemicals to highlight the downside of a slow-moving regulatory risk assessment system. Because many “safer” chemical schemes are driven by lists of hazardous chemicals assembled by State or Federal agencies, chemicals that have not yet been officially assessed or placed on a list may be considered risk-free.  For example, EPA’s recent risk assessment of perchlorethylene, long the predominant solvent used in dry cleaning, concluded that the chemical is a likely human carcinogen and poses a potential hazard to human reproduction and development and to kidney and liver health. Many dry cleaners have now switched from perchlorethylene to n-propyl bromide, a chemical not yet on official lists of hazardous materials, although research suggests it may actually pose a greater health risk than perchlorethylene. Because EPA or state risk assessors haven’t conducted a formal risk assessment for the alternative chemical (a process that can take several years), manufacturers may be assuming it’s safer, when in fact the opposite may be true.

In their commentary, Gray and Cohen urge EPA to alter its approach to risk evaluation and “offer faster summaries for more chemicals.” In his research, Gray is investigating ways to assess chemicals’ safety more efficiently, so that both public- and private-sector decisionmakers can get faster answers to questions about products’ relative safety.

One project, which Gray is conducting along with DrPH student Beth Holman, is analyzing the tests conducted on pesticides to determine which ones EPA relies on most heavily to set pesticide exposure limits. “Right now, EPA requires many toxicity tests, and some of them are very resource-intensive,” explains Gray. “If it turns out that only a few tests actually drive the toxicity values that are eventually set, we may be able to be more efficient in developing exposure limits.  We can also begin to characterize how uncertain we are about risk values depending on which tests are available.”  The study is currently in press at Human and Ecological Risk Assessment.  Gray, Holman and postdoctoral scientist Bing Wang are also investigating the potential for estimating reliable risk values from shorter-term tests, again with the goal of developing approaches to do faster “rough and ready” risk values on more chemicals.  

With hundreds of new chemicals entering the market each year and retailers demanding substitutions for chemicals like the plasticizer bisphenol A (BPA), taking several years to reach conclusions about an individual chemical can mean that more-dangerous alternatives make it into wide circulation before a regulatory risk assessment is conducted. 

Changing regulatory risk assessment procedures could take many years, but manufacturers can immediately start making use of information on chemicals’ relative safety. “Walmart’s telling their supply chain they want certain chemicals out of their products, and if I’m a supplier, I want to fix my product so they’ll accept it,” Gray explains. “I want to make a good decision about what I’m going to put in there, but I need an answer quickly about the available alternatives and what the different risks are.” That’s the gap Gray and his colleagues are working to fill.

Addressing tradeoffs

Choosing an alternative is rarely as straightforward as choosing chemical X because it’s safer than chemical Y in every way, Gray warns. Engineered nanomaterials are an example of a new technology with many potential benefits but risks that need to be managed.  These materials, which are intentionally produced to have at least one dimension that is between one and one hundred nanometers (roughly 100,000 times smaller than the diameter of a human hair), can be used to produce items that are lightweight and strong, are more energy efficient, or have other desirable properties.

“With engineered nanomaterials, we have all these new molecular entities, and we’re still learning about how they behave and how they might affect workers and the environment,” says Gray, who received a National Science Foundation grant to run the workshop “Strategies for Setting Occupational Exposure Limits for Engineered Nanomaterials” at GW and co-chaired the Federal Nanotechnology Environmental Health Initiative while he was at EPA. “There are a lot of ways engineered nanomaterials can be used to improve public health – for instance, improving water quality in developing countries.”

 At the same time, concerns about potential health effects mean sound risk management is needed. 

“To make a good decision, people need to know what the risks and benefits are, and consider whether it’s feasible to address the new hazards you might be introducing,” says Gray. “No chemical is going to be best on all of the attributes, so we need a system that lets us characterize the risks, be clear about tradeoffs and make decisions in a transparent way.”