Transcript
This is a transcript of the May Podcast
This is a podcast from Informa Healthcare. Connecting toxicology to today’s world, we welcome you to this Informa Healthcare ToxiCast with Dr. Steven Gilbert.
Host: People come into contact every day with countless substances that could at certain concentrations or amounts be toxic. This applies to well-known substances such as mercury, lead, radon, and alcohol, but also to a seemingly harmless compound such as caffeine. Why are some people more sensitive to the effects of caffeine than others? Why is a developing infant much more susceptible to the dangers of lead or mercury? How does the science of toxicology touch our lives everyday?
We are joined today by Dr. Steven Gilbert, whose book A Small Dose of Toxicology sets out to answer these questions by setting toxicology in a human context and focusing on the health effects of common toxic agents in the home and the environment. Dr. Gilbert is the Director of the Institute of Neurotoxicology and Neurological Disorders located in Seattle, and Affiliate Associate Professor at the University of Washington’s Department of Environmental and Occupational Health Services.
Dr. Gilbert, what was your main purpose and primary aim in writing A Small Dose of Toxicology?
Dr. Gilbert: My goal in writing this book was to try to make toxicological information accessible to the general public. We’re exposed to a range of chemicals in our daily lives, from the food we eat, the toys we play with, the air we breathe, the water we drink, and I think we need to know a little more about the health effects of common chemicals, how we can prevent the consequences of our exposure to these chemicals.
Host: Who exactly is the intended audience for your book?
Dr. Gilbert: I had a broad audience in mind, from the general public to the media, to legislatures and their staff, to teachers and students—so there’s wide range of people, even health professionals that are making policy-related decisions or working in the field. Toxicology is a huge, complicated field and I tried to write a book that was easily accessible with information that people could turn to. They don’t have to read the whole book in one stance. They can just flip through the chapter of interest, like if you’re interested in mercury or lead or PCBs you can go to that chapter and learn a little bit about that subject and if you want to learn more there’s many references and other material that will take you deeper into the subject.
Host: What specific toxicological concepts come into play in people’s daily lives?
Dr. Gilbert: Well some of the most important ones are dose-response. We respond to specific doses of a chemical. Take for example caffeine, many of us consume a bit of caffeine, and we respond to that and we like the stimulatory effects. But we can also drink too much caffeine and that’s the adverse consequence. So the interest of toxicology is the dose and the adverse response we get from a specific exposure.
Host: Okay, in the first chapter of the book you mention that toxicology has shifted its focus from emphasizing high dose chemical exposures that cause death to risks associated with low-dose exposure with the knowledge that even small amounts of a chemical can cause brain damage in a developing child. What accounts for this historical shift in focus? How are effects of harmful exposure to toxins and toxicants measured in humans and how are acceptable levels of risk determined?
Dr. Gilbert: Well that’s a huge question. That really important shift occurred in the last couple decades. One example is around lead where we gradually learned that the high consequences of lead exposure are visible and can result in death for a child but the real consequences of lead exposure are the low-dose effects and the effects on development and learning and memory disabilities. So we want to study more effects like that. Mercury is another example and almost every compound we study in toxicology we start off looking at the high doses and look at the gross body effects, gross organ deficits and then we start looking at the more subtle consequences, whether its immune system function, neurobehavioral deficits, or even cancer; and we learn that even small amounts of exposure to certain chemicals can cause these deficits. So that’s been a very important lesson in toxicology and one we’re still learning. We arrived at that both with experimentation on animals but also with experience with humans.
Host: One of the things that you mentioned there also was the risk of mercury exposure, particularly we hear in the fish we eat. How big of a threat do you feel mercury is?
Dr. Gilbert: I think mercury is a threat. We learned from experience in Minamata, Japan and Iraq that even small levels of mercury exposure can retard the development of the fetus and the child. And mercury exposure comes from a variety of sources. One is with the fish that we consume but the start of this mercury, for example, comes from coal-fired utility plants where the coal has a bit of mercury in it. We know how to control the ethanol coming out of coal-burning utility plants and we can do that. We need to do that to reduce the amount of mercury that gets into the food supply. Because right now corporations externalize the cost of their product onto children and women of child-bearing age and they have to accept the consequences of mercury exposure. And we know what we can do about it.
Host: One of the other things you mention too was lead and of course lead was once added to gasoline and used in paint, which is still a source of childhood lead exposure, but recently lead has been found in children’s toys. Can you briefly explain why low-dose exposure to lead is so hazardous to children and why they are more susceptible?
Dr. Gilbert: Yes, lead is a fascinating story and has an enormous history to it. We knew 2,000 years ago that lead makes the mind give way and yet we continue to put it in paint. I just want to point out that Europe actually banned lead-based paint in 1922 with the League of Nations while the United States continued to allow lead-based paint right up until 1978. And children are exquisitely sensitive to the health effects of lead because, for one thing lead substitutes for calcium, so children because of their growing bodies need a lot of calcium. So they actually absorb about 50 percent of the lead they ingest compared to an adult who would only absorb about 10 percent of that lead. So right there children are more susceptible to lead exposure because they absorb more lead when they ingest it. Also their nervous systems are developing, so their cells are still changing and growing and dividing, and lead affects that. In addition their small size means that even a small exposure to lead translates into high-dose of lead exposure, so a small amount of lead exposure means it’s a high dose. And children eat more, breathe more, and consume more per body weight than adults do.
Host: Well let’s go back to dose-response, because in your book one of the basic principles of toxicology is that the amount of exposure or dose determines the beneficial or harmful effects of a substance, commonly referred to as dose-response. Could you briefly explain the principle? How is dose-response tested for in humans and what factors do an individual’s sensitivity depend on?
Dr. Gilbert: Dose-response is a fundamental principle of toxicology, and I think one of the easiest examples is caffeine or alcohol. Many people consume these compounds. With caffeine we consume a bit of coffee and coffee has about 100 milligrams of caffeine per cup in it. We consume that for its stimulatory effects and we like that so that’s the beneficial part of caffeine consumption. But when we consume a little bit too much it can make us a little bit jittery, a little bit hypersensitive and we dislike that effect. So that’s the adverse effect. And we learn from experience how to titrate our dose, how to moderate our dose of caffeine. And we also have learned with caffeine use that if you stop drinking caffeine some people get headaches, many people have experienced that so that is another consequence of drug exposure where we actually consume caffeine to avoid headache. If you think about those principles and the other principle of toxicology is half-life, and that’s how fast the compound is metabolized. And caffeine has a half-life of about 4 to 5 hours, so it’s relatively quick so think about the properties of this drug. You’ve got caffeine, you consume it, you can’t consume too much at any one time because you get the adverse effects of it, and you have to keep consuming it to keep your caffeine levels up to get the response you wish so you have to come back and drink more, and you can’t stop drinking it because you get headache. These factors really translate into why caffeine is such a great drug to make money from. And it is a very good drug, but Starbucks and the coffee companies and cola companies all make a fortune off these properties of caffeine. So that briefly explains dose-response. In toxicology, we look for those same principles in lead, mercury, PCBs, other cancer-causing agents. What is the dose that might produce either the beneficial and the adverse response?
Host: That’s funny, because in your book, in your chapter on caffeine, you do say that there hasn’t been a better drug designed to make money from. And I think I understand why. And then you end your book with a chapter on risk assessment and management in toxicology and introduce the precautionary principle. Briefly explain this concept and why is it integral to avoiding risk in the future and the cost to society?
Dr. Gilbert: You know that’s a really good point. I think risk management and understanding the dose-response principles and turning that into risk assessment is really important and the precautionary principle comes into play because we really need to move toward preventing disease. We have a great history in our society of working on treatment, we have a great medical society that works on the treatment of disease and we really need to move toward a preventative society. And the precautionary principle states that when an activity raises threats of harm to human health, I want to emphasize threats of harm to human health, or the environment, precautionary measures should be taken even if some cause and effect relationship are not fully established scientifically. So that means that even if there is some uncertainty, we must take action. A great example of this is cigarettes and smoking where we knew for a long time that cigarettes cause cancer but industry and others did a great job of sort of clouding that issue and not getting that out there and we didn’t take the preventative action. We are starting to do that now.
So there are several principles of the precautionary principle that come about, several elements of the precautionary principle. One is setting goals, we want to set health indicators of goals out there. For example we might want to set a goal of reducing asthma by half by 2020. We want to take preventative action in the face of uncertainty, we want to take action even if we aren’t totally sure about it. For example, with lead, as I mentioned earlier the European League of Nations banned lead-based paint in 1922. They took a precautionary approach to lead and the United States didn’t do that for a long time. Same with getting lead out of gasoline. We shouldn’t have ever put lead in gasoline. It took us a long time to get it out. We also have to shift the burden of responsibility to the proponents of an activity. The Food and Drug Administration that authorizes drug sales in the United States has a very precautionary approach. The pharmaceutical and biotechnology industry has to submit reams of data to show efficacy, effectiveness of the compound as well as safety. We don’t have a similar approach when it comes to industrial chemicals. We also want to explore alternatives. Many times we don’t need to do what we’re doing. We can have a different approach to things. For example, some of you might have heard about brominated flame retardants. Either the retardants that are in our mattresses and our cushions. A lot of these chemicals are put there because cigarettes burn and cigarettes burn because the tobacco industry put accelerants in our cigarettes.
We have alternatives, we don’t need to go through putting flame retardants in our pajamas because lead in wool are good natural fire retardants. And we also have to expand our democratic process and inform people, make people more aware. And that’s one reason I wrote the book, A Small Dose of Toxicology, was to make people more aware of these principles and help people make better policy-related decisions.
Host: With the overall concern for children’s health, what is our ethical responsibility to this issue?
Dr. Gilbert: I think we have a really important responsibility to children. Children have the right to an environment where they can reach and maintain their full potential. And really all species do. We have incredible power to distribute chemicals around the environment and control the development of many species. And children in particular, when we expose them to lead or mercury or alcohol in utero, or a little bit of PCBs, or a little bit of brominated flame retardants, the whole alphabet soup, we really rob them of their potential. And this I think is something we really need to be paying attention to and we need to devote more resources to understanding this and really protecting our children’s health by not exposing them to any of these chemicals.
Host: Also Dr. Gilbert, is there a website that listeners can go to?
Dr. Gilbert: Yes, I did a website related to the book -- www.asmalldoseof.org. And this website has a PowerPoint presentation for each chapter of the book. And I did this for both students and teachers so they can go in there and use the material. Any material on the website is free to download as well as additional material on other subjects related to the book. I also have another website called Toxipedia – www.toxipedia.org, which is a wiki-based site that allows people to add information and update information on toxic chemicals, but it’s a reviewed site so it should be a site that people can refer to with confidence in the information that they see there.
Host: Dr. Gilbert it’s been a pleasure talking with you. I think we’ve learned a lot.
Dr. Gilbert: It’s great, I really appreciate you taking the time to do this and I hope your listeners learned a little more about toxicology and received a small dose in this effort.
Host: For more information on purchasing this book or other podcast subjects offered by Informa Healthcare, go to ToxiCast.com, connecting toxicology to today’s world.
This has been a toxicology podcast from Informa Healthcare.
Thanks for listening.