Because those who argue that sound science means that we have to have absolute unequivocal evidence, with no contrary evidence, aren't scientists; they're politicians or lobbyists.
I work with scientists every day. The people on our committee include, for example, Dr. Paul Demers, who was one of the leading epidemiologists in Canada and is on the IARC panels in Geneva at the World Health Organization that classify the carcinogens we're talking about, and Paul is a well-known classifier. So Canada references these same classifications in this legislation right across the country. Paul wrote the piece on best practices about that, saying that in fact if we want to talk about identifying risk.... In our world today, it is not science at all to say the risk is x or the risk is y. It depends on who you're talking about.
We didn't talk today about vulnerable populations or people who are more exposed and people who are less exposed. We're worried about protecting people from a reproductive hazard or a carcinogen. If they have no exposure, then we don't really have to worry about it. But we know that across the country there are pockets and elements in communities, or whole groups of people, that are at higher risk because they are exposed, and that's where you take action and that's why you use precaution.
So if somebody wants to argue with me, or with the health scientists we work with, about sound science, not only would we not have moved on secondary tobacco smoke, but also not on tobacco legislation at all, because the industry always claimed there wasn't enough sound science to even label it. We wouldn't even have moved on pesticides, to which there was reference made earlier.
If you use the term “sound science” to mean there has to be unequivocal evidence that people using cosmetic pesticides on their lawns are going to cause X, Y, and Z, we wouldn't have a municipality in the country that would have banned cosmetic use of pesticides.