No one is going to deny the cancer-causing potential of industrial, agricultural and consumer chemicals.
What's at issue is actual human risk from exposure to these chemicals in our daily environment.
And even if a chemical or substance has been proven to be harmful, there's no guarantee that a legislative body or regulatory agency will severely limit or ban its use. Consider the ongoing national debate over the sale and use of tobacco.
"You have industries saying, 'we can't afford to meet this regulation and it'll put us out of business, you have to be a little bit more lax,'" said Allan Hirsch, spokesman for the Office of Environmental Health Hazard Assessment (OEHHA) in California. "The regulatory agencies are in the position of having to decide how strict a regulation has to be, and at what cost -- what's it going to do to the cost of products? What's it going to do to jobs?"
The debate over risk management can be so contentious and politicized, there are legitimate concerns it can interfere with the pure science of risk assessment.
For this reason, Hirsch said, when the California Environmental Protection Agency was formed in 1991, OEHHA was kept a distinct entity "specifically so that we could practice risk assessment, and not be part of a government agency that is making regulatory -- also known as risk management -- decisions."
The process of risk assessment is remarkably simple in concept, and astonishingly complex in scale and scope.
According to Dr. Lauren Zeise, chief of reproductive and cancer hazard assessment at OEHHA, there are four essential steps:
Hazard identification -- Gather all the information you can on a chemical and sort out what "end points," or health effects, are your concern. Is it a carcinogen? Does it cause reproductive problems, delayed neurological development or acute lung toxicity?
Dose response -- This step determines what happens when individuals and populations are exposed to a chemical. Different levels of exposure cause different levels of effects, both qualitative (where higher doses provoke more severe responses in the individual) and quantitative (the higher the dose, the more people affected).
Exposure assessment -- How much actual exposure to this chemical is occuring in the real world? Is it site-specific -- related to, for example, a single factory or waste dump near a particular neighborhood? Or is it related to a product or process (like the use of agricultural or lawn pesticides) that is far more widespread?
Risk characterization -- At this point the scientist puts all the pieces together. What kind of exposure is going on? What are the risks to, say, the elderly, or to children?
The whole process can take anywhere from a few months to several years or more. OEHHA's study of the health risks of diesel exhaust (oehha.org/), for example, took nine years.
Once the four steps are complete, with the results written up into a report and delivered to the appropriate regulatory agency, the job of the risk-assessment scientist is essentially over.
"Risk assessments do not typically include recommendations," said Hirsch. "They would typically say, 'the public faces this kind of risk from exposure to a chemical at this level' ... then it's up to the regulatory agency to decide what is an acceptable level of exposure and what kind of regulations ought to be enacted."
And this is the point where things get very, very political.
"There are about a hundred chemicals that cause mammary tumors in mice," says The Breast Cancer Fund's public-policy advocate Joan Reiss, "and they're still on the market and we're using them broadly, were not taking that seriously ... people say 'it's just animals and doesn't mean anything.' I think that if we have associations in the federal government that are listing these things as number one carcinogens, then they should be banned. It's not a matter of let's do more tests, these things should be banned. But we're not at that stage yet and we have a very powerful chemical industry."
Political indeed. One can't help but wonder how the scientists themselves react to the regulatory decisions made based on their research.
It's a difficult question that Zeise and Hirsch keep scrupulously distinct from their capacities as professionals and state employees.
"As individuals I'm sure the various scientists here each have their own feelings, personal feelings, about what ought to be done to abate the risks that we identify," said Hirsch. "As an agency we have to be satisfied with identifying risks, and then handing that off to another agency."