University of Toronto Magazine University of Toronto Magazine
Bottle caps
Photo by Dougal Watters/Getty Images

Environmental Toxins

Q&A with Miriam Diamond, co-chair of Ontario's Toxics Reduction Scientific Expert Panel

Geography professor Miriam Diamond studies how chemicals travel through the environment and enter the human body. Last March, Diamond was appointed co-chair of Ontario’s Toxics Reduction Scientific Expert Panel to help create a provincial strategy for reducing toxins in the environment. She recently answered questions about the complexity of that task.

There are thousands of chemicals in our air, food, water and the goods we purchase. How do you even begin to determine which ones pose the greatest risk?
We look at how much of the chemical is produced and whether it is likely to hang around in the environment. Can it accumulate at high levels in organisms such as fish? Is it toxic at the levels humans are exposed to? That’s often difficult to answer. Toxicologists all over the world are trying to figure out what the effects of these chemicals are on animals in the ecosystem and on humans. We look at their studies.

Quite often chemicals that are initially thought to be safe turn out not to be. Why?
There’s a big difference between how a small amount of a chemical behaves in a lab test when it’s being examined for approval and what happens when large amounts are released into the environment. In the years immediately following the Second World War, when a lot of chemicals were approved, we didn’t know how far-reaching their effects could be.

A big mind shift occurred in 1962, with the publication of Rachel Carson’s book Silent Spring. Carson, an ecologist, showed that pesticides intended for use on agricultural products were not staying put – that a pesticide intended to eradicate a bug in a field was also thinning the shells of hawk eggs. Her book was a wake-up call to the complexity of chemical behaviour in the ecosystem.

Another mind shift came when Theo Colbourn published Our Stolen Future, which put the story together that very low levels of toxic chemicals could affect the developing fetus. Other authors went on to show that kids as well as the fetus are most vulnerable to a chemical’s toxic effects.

There are circumstances in which we should move to ban a chemical, based on a weight of evidence suggesting that we could be exposed — or the ecosystem could be exposed — to levels that could be hazardous. Many, if not most, chemicals can be hazardous; that’s not totally the point. The point is whether it’s possible to be exposed at levels that could cause health risks.

Let’s talk about a specific case of a chemical that was first approved and then banned: PCBs, for example. Tell me what happened there.
PCBs, or polychlorinated biphenyls, were introduced in the late 1940s as insulating liquids for electrical transformers and capacitors. They improved safety. By the late 1960s, PCBs were also widely used as plasticizers in building sealants. It was discovered that they made outdoor paint more stable, so it didn’t flake off or fall apart. They were used in carbonless copy paper, and all sorts of applications.

By the early 1970s, though, chemists started finding them in the environment far away from where they were being used. They started showing up all over the place and various wildlife populations, such as the mink around the lower Great Lakes, were failing. Only recently did scientists hypothesize that this was connected to PCBs. Occupationally, PCBs were known to make people dizzy and cause headaches. It was much later – and it’s still emerging – that PCBs can disrupt the developing fetus and consequently, can have long lasting effects. They may cause memory loss in middle age. They can affect the immune system and reduce fertility. There are delayed and subtle effects that one would never have thought could be due to PCBs.

Wasn’t there any indication at the time that exposure to PCBs could have negative health effects?
There was some, but the full understanding still hasn’t come out. Scientists are now wondering whether PCBs are related to ADHD because the behaviour of rats and mice exposed to PCBs is similar to the behaviour of ADHD kids. Several studies have unfortunately shown that kids of moms who ate a lot of Great Lakes fish which were high in PCBs and mercury have lower IQs and behavioural difficulties.

So, to return to the question of how to determine whether a chemical poses a risk: It’s not simply a matter of exposing an organism, waiting, then checking to see whether it’s alive or dead. For a fish, it’s a matter of determining whether its exposure as a little egg can allow the adult fish to find its food. For humans, its much more complicated and none of us wants to be the test subject!

We’ve been hearing a lot recently about Bisphenol A. Tell me about the problems with it.
Bisphenol A is used in CDs, cell phones, water bottles, car parts, glues and the epoxy lining in tin cans, among many other things. Worldwide production has been increasing at 6%-10% a year.

Four thousand studies have been done on Bisphenol A and there’s still a raging controversy over its health effects. What’s emerging now is concern for several chemicals that are produced in very large amounts. These need to undergo a battery of tests but history has shown that we may not be able to capture all the potentially bad effects. The problem is not just Bisphenol A, but that we use it in so many applications.

Are there standard tests performed on these chemicals before they are approved?
It depends on how much of the chemical is to be produced, but less information is required than you might think. There are some inconsistencies and loopholes in federal regulations, especially with respect to imported products. Think of all the recent recalls on toys with higher-than-allowed lead concentrations. We’ve known that lead is a potent toxin since the time of the Romans, and globally, we still have kids toys with high lead levels!

How do Ontario’s standards for regulating pollutants and possibly toxic chemicals compare with standards in other jurisdictions?
The expert panel has worked with the provincial Ministry of the Environment to propose a toxic reduction strategy for Ontario, which I think is very exciting because it’s not just a chemical-by-chemical review. It aims to improve industrial and manufacturing technologies. The expert panel’s mandate is to look at a strategy for reducing toxics as a whole and promoting a green economy. I think this is a very good approach because we need to implement pollution prevention steps in manufacturing. We need to do produce and manage our chemicals in a smarter way. We need to start at the very beginning when we’re designing chemicals and designing products, and when we’re disposing products. Let’s think holistically. What are the implications of using this chemical in commercial products? Could it create a byproduct that’s nasty? Could it migrate out of a product when it’s dumped somewhere? As we do this, let’s pump up our economy and pump up creativity and innovation in Ontario. That’s what the strategy is about.

We all need to eat, breathe and drink water. Is there anything individuals can do to reduce their exposure to potentially harmful chemicals?
It’s very hard to act individually to reduce your exposure. Toxic chemicals are all over the place. We produce toxics when we drive our cars, especially the larger cars, vans and SUVs. We can minimize our use of plastic packaging, avoid putting plastic in the microwave, avoid carpets in our home and reduce dust content. We can purchase fewer short-lived and relatively useless products. In other words, we can buy more durable products only when we truly need them. This doesn’t mean sending the economy into a tailspin, but rather spending a little more on products that last longer. As individuals, we must realize that frequent driving and living in large homes full of short-lived products increases our exposure to toxic chemicals.

However, what we really need to do is act on a societal level. We need to vote in governments with strong and coherent environmental policies that are central to their overall ambitions. It’s unfair to put the onus on individuals because the issues are very complicated. A recent study by Nora McKendrick, a PhD student in sociology, found that in the past decade the message around health and environmental issues has become individualized. The focus is on what you can do. But the issues are becoming more and more complex, which makes it harder for individuals to take steps and necessitates an overall societal strategy that is orchestrated by visionary government leadership.

A shorter version of this interview appeared in the Winter 2009 issue of U of T Magazine. To find out more about the Toxics Reduction Scientific Expert Panel, visit

Recent Posts

Leave a Reply

Your email address will not be published. Required fields are marked *