Risk vs. Hazard
At the heart of responsible chemicals management are two concepts – hazard and risk. In basic terms, hazard is the potential of something to cause harm, while risk is the likelihood of harm occurring. For example, a tiger is inherently hazardous; however, a tiger living in India poses little risk of harm to a person living in the United States.
Similarly, the intrinsic hazard of a specific chemical ingredient in a product does not itself determine whether or not that product is “safe.”
Rather, the risk to human health, for example, associated with a hazardous chemical ingredient in a product will depend not only on the presence of the chemical, but also on the nature and extent of any potential human exposure to that chemical from the reasonably anticipated uses of that product.
Additionally, eliminating a hazardous chemical ingredient from a product may not necessarily ensure that the product is now “safe.” Sometimes, eliminating a “hazardous” chemical ingredient can lead to replacing it with an ingredient that is actually more likely to pose a risk.
Making decisions about using a specific chemical ingredient in a product based on that chemical’s hazard profile alone may seem simple and straightforward. But such decisions often ignore the best available science and can have negative consequences, including possibly causing greater harm to people or the environment. Therefore, the solution isn’t necessarily to eliminate the hazard alone, but rather understand how to properly manage potential risks.
That’s why scientists often undertake a “Risk Assessment,” an analysis of a chemical ingredient’s inherent hazard profile, along with the exposure potential, to help establish the probability of an adverse effect resulting from a specific use.
The next sections outline:
- Some tools and methods scientists use to identify chemical hazards, and the role hazard identification plays in risk assessments.
- Examples of possible consequences that can occur as a result of hazard-based decision making.
- The value of risk assessments and steps scientists take to conduct a risk assessment
So how do we know whether specific chemical ingredients in products have the potential to cause harm? Scientists can identify chemical hazards through experimental testing in laboratory animals and cellular systems, as well as through computer simulation and modeling. Given the potential for uncertainty, scientists design and conduct tests and models to over-predict hazards, to help protect human health.
Hazards can also be determined through observational studies of humans who have had unusually high exposures to a certain substance. Such studies, known as epidemiology studies, have sometimes yielded important results, but are typically considered less reliable, more difficult to interpret and more prone to error.
Why Hazard Alone Cannot Reliably Determine Risk
Hazard identification is but the first step in a risk assessment. So, to make decisions based on hazard alone ignores other important scientific information. A simplified example may help illustrate this:
Let’s hypothesize that an aircraft parts manufacturer is trying to responsibly choose the “safest” solvent available for removing grease from metal parts. After thorough research, two nearly equally effective options are identified, Solvent A and Solvent B. Solvent A produces a toxic effect at half the dose of Solvent B and would initially seem to be the “safer” choice, based on hazard alone.
However, scientific data indicates that Solvent A evaporates into the atmosphere at 10 times the rate as Solvent B. Thus, workers using Solvent A would have 10 times the exposure to it than they would to Solvent B, and thus 5 times the likelihood of incurring actual harm.
Therefore, contrary to the results of the hazard alone decision, choosing Solvent B based on this sort of risk assessment would actually lead to a “safer” workplace.
While scientific methods for identifying hazards continue to be improved, they remain a work in progress due to inconsistencies and uncertainties. Expert judgment is often required to assess all of the evidence available to inform responsible decision-making. Hasty decisions based on preliminary scientific evidence, even when made with the best of intentions, can lead – and have already led – to regrettable outcomes.
Consider the following real-world examples:
- Misplaced fears about potential hazards of chlorination byproducts led to an outbreak of deadly cholera in Peru and other Latin American countries in the 1990s.
- Parents choosing not to vaccinate their children against a host of diseases – largely based on fraudulent research linking vaccines or their ingredients to autism – has led to a growing incidence of preventable communicable diseases.
- Classifying and labeling chemicals based on their hazard properties alone (e.g., carcinogenic, mutagenic or reproductive toxicity), and illustrating products with scary symbols or signage may unfairly stigmatize products and deter people from using them, even if any potential exposures could be effectively managed for safe use.
- Consumer products manufacturers and retailers succumbing to pressure to eliminate certain chemicals from products based on either real or perceived hazard properties, without having evaluated whether they truly pose a risk when used as intended.
Decisions made based on hazard alone can also have other negative consequences such as loss of “safer” beneficial products from the marketplace, substitution with less “safe” products, higher costs for consumers, and disincentives to innovate safer products.
A risk-based chemicals management approach can successfully balance safety and benefits and can effectively help one determine the “safest” choice among multiple options. That is why nearly every regulatory agency around the globe, and chemical manufacturers themselves, practice risk-based chemical management.
The U.S. National Academy of Sciences (NAS) has repeatedly and consistently affirmed its support for risk-based decision making as the preferred approach to chemicals management. In 1983, NAS first outlined the steps in a proper risk assessment, and later reaffirmed this process in 2009, while also acknowledging some challenges (e.g., increasing complexity, length of time required, reliance on default assumptions in the absence of data, and disenfranchisement of some stakeholders), and offered some suggestions to help overcome them. The World Health Organization (WHO) also strongly advocates for a risk-based approach to chemicals management.
The term “risk assessment” can encompass both qualitative and quantitative approaches. Indeed, the majority of risk assessments undertaken are screening level assessments that use a host of conservative assumptions designed to be overprotective, and can often be done quickly and inexpensively.
Conducting a Scientific Risk Assessment
Experts generally agree on the following four steps to a proper scientific risk assessment:
- Hazard Identification: Scientists rarely have definitive evidence that a specific chemical directly causes a particular disease. Therefore, experts rely on data from experimental testing in laboratory animals and cellular systems, as well as computer simulation and modeling. Given the potential for uncertainty, scientists design and conduct tests and models to over-predict hazards, to help protect human health.
- Dose Response Assessment: This takes into account intensity, duration, timing, age, gender, lifestyle and other factors and often involves extrapolation from observed doses to lower doses using health protective assumptions.
- Exposure Assessment: Characterizes the magnitude, duration, schedule and route of exposure; the size, nature and classes of population exposed; and the uncertainty in all of the estimates.
- Risk Characterization: The process of estimating disease incidence under each exposure scenario identified in an Exposure Assessment. It combines the exposure and dose-response assessments and also summarizes the uncertainties in the prior steps.
Despite the scientific strengths of risk assessment, the outcomes should not necessarily be accepted at face value, and the underlying data, analyses and assumptions should be carefully scrutinized in order to fully understand the conclusions that are being asserted.
According to the National Academy of Sciences, “Risk assessment provides an effective framework for determining the relative urgency of problems and the allocation of resources to reduce risks. Using the results of risk analyses, we can target prevention, remediation, or control efforts toward areas, sources, or situations in which the greatest risk reductions can be achieved with the resources available.
“However, risk assessment is not an absolute procedure carried out in a vacuum; rather, it is an evaluative, multifaceted, comparative process. Thus, to evaluate risk, we must inevitably compare one risk with a host of others.”