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Understanding Toxicology

Understanding Toxicology

Gary Ginsberg (Toxicologist) gives expert video advice on: What is 'toxicology'?; How are toxicology studies conducted?; What is 'epidemiology'? and more...

What is 'toxicology'?

Toxicology is the scientific study of the harmful or damaging effects of chemicals that can be found in our environment, or in the indoor: homes, schools, workplace. How these chemicals can affect systems like the nervous system, reproductive system. Whether they cause birth defects. Whether they can even cause lethality, acute mortality, killing people, because we know that at high doses some things can be so toxic that they can actually cause immediate death. But most things that we're exposed to are affecting us over the longer term, may lead to a cancer risk. And so our studies in animals can show us the toxic potential of a chemical.

How are toxicology studies conducted?

Mostly from animal studies because we don't want to intentionally expose people to these chemicals. And often times what happens in an animal system will also be relevant to what happens in children, older folks, pregnant women. We can study all those kinds of affects in animals and relate that to the human risk.

What is 'epidemiology'?

We can get a sense of what epidemiology means by the root word DEM, which is from Greek meaning people. So it's the pattern of disease in the human population, and it can be from infectious agents, or it can be from environmental contaminants. So what we're talking about today, it's the study of how populations of people can become ill, and have adverse health affects from toxic chemicals, whether it's from the work place or whether, it's again, from other ways that they can be exposed in their neighborhoods around their home. So it's the pattern of disease in the human population from toxic chemical exposure.

What are the connections between toxicology and epidemiology?

Toxicology allows us to understand the hazard potential in animals. But sometimes the animals respond differently. And we're talking about rats and mice now, mostly. They can respond differently than human populations. So it's very important to try to get confirmatory information from populations of people also exposed. And if they respond similarly to the animals, well then that gives us more confidence that perhaps we need to take an intervention measure and stop populations of people from being exposed to this chemical. For example, chloroform in drinking water has been shown in animal studies to be a carcinogen, and also to have some reproductive health effects. Well, many people are exposed to chloroform in drinking water, because of chlorination of water supplies. And some studies have shown similar effects in human populations, which is why we have recommendations about filtering your drinking water.

What are the differences between toxicology and epidemiology?

Toxicology and epidemiology differ in the fact that one is focusing often on animals, the other is focusing on human populations. But besides that, in toxicology, because you are working on experimental animals, you know exactly how much dose you are giving them, so it's easier to understand what we call "dose response" -- how potent something is. Whereas in epidemiology, people are variable. You try to understand how they are exposed, and you don't often know the dose that one person is getting versus another person. You have to make estimates of that, so it is less exact in terms of understanding the potency of a chemical to produce an effect in a human population study, just because you don't know exactly how they are exposed.

What is meant by the term 'risk assessment'?

Risk assessment is putting together the variety of different kinds of information from exposure, how much someone is actually getting exposed to, whether it's from their diet, drinking water, food supply. Combining all these pathways of exposure you get an internal dose, but what does that dose mean? Well you have to look at the toxicology to understand the potency of the chemical. When you put together the exposure dose and the potency, combining those two together you can come up with an estimate of risk. How likely is it that that person, exposed to that dose, will either get cancer, or will there be birth defects, or maybe some nerve damage.

How is risk assessment measured?

Risk assessment is given in terms for the probability outcome of a damaging effect. So we say the risk for getting cancer by living next to the super front site may be 1 in 100,000 or 1 in a million. That is the odds of getting that adverse effect. So it is a probabilistic estimate of how risky it is to be doing that activity. For example, person A may be living right next to a toxic waste site and having the gases from that site coming over the fence line into their home. They may be at a cancer risk that is 1 in 100. That is much riskier than someone who; lives 3 miles away; may still be getting some fumes from that site; but they are at a much lower risk dose. Their risk may be 1 in a million; much lower exposure level' much lower risk. So that is the value of risk assessment. It puts the risks for different people into the same yardstick, the same measurement device, puts them all into context.

What is a 'carcinogen'?

A carcinogen is a chemical that causes cancer or tumors, because the exposure is affecting the way your body works. It could damage DNA, and that leads to the longterm risk of increasing your chances for getting cancer.

What is a 'risk comparison'?

A risk comparison is when you are comparing the risks from one kind of exposure to another kind of exposure so that you can evaluate what is something that you want to avoid...what is a higher priority to avoid and what is an exposure that may be a lower priority. What we have to watch out for are when you are making apples to oranges risk comparisons. So if your doctor says to you "Well the risks from getting into a car accident are greater on your way to my office than the risk from you eating tuna fish during pregnancy because of the mercury in the tuna fish" if that's an apples to oranges kinds of comparison then you may as the pregnant mother be more willing to take the calculated risk of doing necessary life activities like driving to the doctor's office then you are willing to take a risk of a chemical exposure to your developing foetus. So risk comparison should only be apples to apples in terms of is the amount of pesticide I am getting when I spray my house to kill bugs, is that a greater exposure and a greater risk than what I am getting in my diet, that helps you prioritize how to cut down on your exposure to toxic chemicals around the home.