Understanding Dose-response The Importance of Dose-response Modeling to the Public William K. Hallman Department of Human Ecology Rutgers University

Dose-response and Regulation Dose-response calculations play an important part in determining regulatory policies However, determining appropriately protective dose-levels is a difficult task

Dose-response and Regulation Decisions regarding regulations based on dose-response must also consider: Available technologies Likely impacts on health Likely impacts on the environment Regulatory and economic burdens Unintended consequences Public understanding, acceptance, and approval

Common Goals for Risk Communication To put risks into context To provide information to help people prepare for or manage risks To understand public concerns To enhance public participation To change beliefs or attitudes To persuade people to take (or not take) particular actions

Understanding Your Audience There is no such thing as “the public” People differ in terms of their: Interest in your message Experience and education Responsibilities Needs and concerns Cultural background

Starting Points In communicating about the potential impacts of microbial risks, it is important to find the right starting points These differ between audiences Efforts should begin with assessments of: What people already know How they know it What they want to know

A Common Mistake Using an expert model of what people need to know as a starting point People are less willing to be “educated” than they are to have their questions answered Experts in the field often assume a level of prior knowledge not shared by the public

What Do People Know? Many have a poor grasp of basic biological, ecological, and environmental concepts But, that doesn’t mean you should give up trying to communicate with the public

Prevention People understand that modern life is not risk-free However: Few people want any additional risks People expect regulators and risk managers to continually work towards zero-risk People want to know how risks can be prevented

Helping People Understand Dose-response Relationships People typically focus on response Familiarity Dreadfulness Likely ‘victims’ Distribution of risks Immediacy of consequences Reversibility Images

Helping People Understand Dose-response Relationships Dose of what? Familiarity Source of the risk Control over exposures Can you know if you are at risk? Is exposure to the risk voluntary? Is exposure to the risk fair? Can I reduce my risk?

Helping People Understand Dose-response Relationships Mental-models Intuitive toxicology Intuitive microbiology Numeracy

Intuitive Toxicology 86% agreed (34% strongly) that “if you are exposed to a toxic chemical substance, then you are likely to suffer adverse health effects.” Kraus, Malmfors, & Slovic Intuitive toxicology: expert and lay judgments of chemical risks. Risk analysis 12(2)

Intuitive Toxicology 34% agreed that “if you are exposed to a carcinogen, then you are likely to get cancer.” 54% agreed that “there is no safe level of exposure to a cancer-causing agent.”

Intuitive Toxicology 36% agreed that “for pesticides, it’s not how much of the chemical you are exposed to that should worry you, but whether or not you are exposed to it at all.”

Intuitive Toxicology 23% believe that reducing the concentration of a possibly harmful chemical in a city’s drinking water would not reduce the danger associated with drinking that water.

Educating Young People Baseline data on th graders in eight states 68% agreed “if you are ever exposed to any amount of a toxic chemical, you will have health problems” Covello,V.T Educating young people about environmental health risks: results from national field trials of the environmental health risk module. In V.H. Sublet et al (eds.), Scientific Uncertainty and its influence on the public communication process, Kluwer.

Educating Young People 75% agreed “the government should spend whatever it takes to eliminate all the risks of chemicals”

Educating Young People 48% agreed “if you are ever exposed to any amount of a chemical that causes cancer, you will get cancer from that exposure”

Educating Young People 52% believe that exposure to a chemical that results in a one in a million increased probability of getting cancer means that one in every million people exposed to the chemical will get cancer

Educating Young People 66% agree that “in treating water with chlorine, it is important to compare the risks of getting cancer from the chlorine with the risk of germs in the water”

Intuitive Microbiology Much of what people know about microbiology is rooted in popular culture Studies suggest that much of what people know about bacteria and viruses come from television advertisements for toothpaste, mouthwash, and household cleaners

Intuitive Microbiology Evidence suggests a new wave of “antisepticonsciousness” Rise in the number of antiseptic and antibacterial products Popular culture suggests “nature is striking back” producing the “revenge of the superbugs” Tomes N The making of a germ panic, then and now. AJPH, 90(2),

Intuitive Microbiology Emotional reactions to microbial contamination are likely to be a combination of both fear and disgust The “ick” factor Cultural assumptions about water, purity, and cleanliness are important Connections between microbial contamination and symptoms are often missed

Numeracy Studies suggest that much of the public has difficulty with mathematical concepts While important, “getting the numbers across” is both difficult and not always the most important message.

Numeracy Many have difficulties with Fractions Proportions Percentages Probabilities Very large and very small numbers

Can The Public Reach The Right Decision? Yes But it depends on what your definition of “right” Public perceptions are unlikely to match expert perceptions

Can the Public Reach the Right Decision? We tend to believe that: others share our values know many of the same things we do are naturally interested in the same things we are We generally overestimate how representative our knowledge and opinions are

Can The Public Reach The Right Decision? We also believe that given the same set of facts, others would come to the same set of conclusions This belief is strongly held by scientists This belief is also socially reinforced We choose friends with similar values and interests who do think much the same way we do In part, this is why we enjoy our associations with them

Can The Public Reach The Right Decision? The result is that we tend to think that everyone does (or should) think the same way we do When we find out that everyone does not think like we do, the natural tendency is to question the competency or motives of those who do not agree with us As a result, it is easy for experts to conclude that the public is inconsistent and “irrational”

Is The Public Irrational? But, the public is not irrational Irrationality implies that the public cannot make decisions about the risks of water-borne contaminants What most surveys suggest is that much of the public has not made decisions about these risks It hasn’t been high on the agenda

Dangers in Believing the Public Is Irrational There are several real dangers in believing that the public is irrational when it comes to making decisions about microbial risks. The first is concluding that since the public is irrational, efforts to provide information and education are a waste of time and money. The second is concluding that since the public is irrational they cannot make “good” decisions. As such, those who are rational (the experts) should make decisions that are “good for the public.”

Dangers in Believing the Public Is Irrational These conclusions are dangerous. The first nearly ensures that the public will not have the tools needed to make informed decisions. The second nearly ensures that the public will become angry that decisions about the acceptability of a perceived risk are being made for them.

Question: How important is dose-response modeling to the public? It can be very important Especially to those who may believe they are most at risk But, people may be less interested in information about how the models were calculated than in information that helps them judge whether to trust the modelers

For More Information: William K. Hallman Department of Human Ecology Rutgers University New Brunswick, NJ (732) x313