The Habitable Planet: A Systems Approach to Environmental Science
Risk, Exposure, and Health Interview with Robin M. Whyatt
Interviewer: Can you tell us who you are and what do you do?
ROBIN: I am Dr. Robin Whyatt. I am an Associate Professor of Clinical Environmental Health Sciences in the Department of Environmental Health Sciences at the Joseph Mailman School of Public Health at Columbia University and I am Deputy Director of the Columbia Center for Children’s Environmental Health. I am a research scientist and I also teach in the School of Public Health, teach graduate students, masters levels and doctoral levels. My research is on the effects of environmental exposures during pregnancy, primarily, and early childhood, particularly pesticides, which are one of the main groups of contaminates that I have been looking at and with a focus on how you measure levels of pesticides during fetal development, which is actually quite challenging.
Interviewer: What got you interested in science?
ROBIN: It is interesting because I grew up at a time when women weren’t expected to go into science and I actually came from a family of scientists. Both my grandparents were quite well known scientists but I went into English. I graduated from college in English and that was what was expected. That was a reasonable career. I mean, it was a good while ago. Fortunately things have really changed in the number of decades since then. But clearly, you know, science was my love and was what I really loved and I think it is because of my family background. I came from a family of scientists and naturalists but it was the men who were the scientists and naturalists at that time. It was when I started doing environmental work where it really came together for me and I realized that it was really science that I was interested in. So, I went back to undergrad and got basically the – my scientific prerequisites. I did organic and then inorganic and organic chemistry and biochemistry. So built the science background up and then from that point on went into science and got the doctorate.
I started out as an environmental advocate. After college I started working for local environmental groups. This was during the time of Earth Day when environmental advocacy was a big thing and it just sang to me. It was coming right from my heart. I did that for about fifteen years, first doing general advocacy work. I became executive director of a small environmental group and, as part of that, I started working on a toxic hotline, and it was at that point that I realized what I was really interested and concerned about was toxic exposures in children. I went back to school and got my masters and then got my doctorate. And then I went to a national environmental group on their staff and was doing a study of pesticide exposures in children and realized at that point that there really wasn’t enough information available to make any conclusions about what the potential health effects were to children. It was then that I, decided to really devote myself to the research and I have been doing it ever since. I have been doing it for about twelve years.
Interviewer: Tell us about your research.
ROBIN: My main area of research is to see whether or not there are any health effects from pesticide exposures at the general level that many people are exposed and whether there are any health effects or not during fetal development. Why did I get interested in that? I got interested in it because a number of these pesticides that we are looking at are insecticides that have been widely used in homes in the United States. There was evidence in laboratory animals at much higher levels of exposure that when these exposures were given during pregnancy when the fetus was developing, there were long term neuro-cognitive problems in the offspring. But that hadn’t really been looked at in human populations and we knew the exposures in humans were much, much below those that we were seeing in the laboratory animals. But because of the results in laboratory animals, it seemed prudent to look in a human population to see whether there were any effects and hopefully we wouldn’t find them.
Very little is known about pesticide exposure from residential abuse—actual use in the home. About eighty five percent of the population does use pesticides in and around their home but it isn’t an area that has really been studied all that much. So we had a number of questions. One is if you use these pesticides in the home, was the mother getting exposed during pregnancy? We were interested in the pregnancy period. Two is, if the mother was getting exposed during pregnancy, was the baby getting exposed during pregnancy? And then the third major question was if the baby was getting exposed during pregnancy, did this exposure have any effect on the baby. Those were really the three research questions we have been looking at.
Interviewer: What were your research questions?
ROBIN: We had four research questions that we were looking at in this study. One is were women using pesticides during pregnancy? If so, were they getting exposed? Those are two different issues. You can be using it and if it isn’t coming into your air or it isn’t getting on you, you won’t have any exposure. The second question is if they were using it, were they being exposed? The third: were the pesticides getting to the baby? And then finally, were they causing any health effects on the baby? What we found is that eighty five percent of the women were using pesticides during pregnancy, that a hundred percent of the women were being exposed to at least four insecticides simultaneously, and about thirty percent of the women were being exposed to all eight insecticides that we were measuring at that time and that the insecticides were being transferred from the mother to the fetus. We detected this one insecticide in particular, chlorpyrifos, which is the one we knew was being used the most, in about seventy percent of the mother’s blood and seventy percent of the babies’ blood.The level in the mother’s blood and the baby’s blood was basically identical and the mothers with the highest levels had the babies with the highest levels. So they were highly correlated. That was a pretty good indication that the compounds were being passed directly through. And then what we found was that the babies that had the highest level of this insecticide had significantly lower weight and length at birth and significantly poor mental and motor development at age three and significantly greater behavioral problems at age three, things like ADHD. That was just with one insecticide, the one that we knew was being used the most. Fortunately it was banned by USDA in the middle of our study so it is no longer being used in residences, which is a very good thing. We are now starting to look at some of the replacement insecticides as well.
Interviewer: Are you looking at this at a local level? national? global?
ROBIN: Certainly the research that we are doing here has had effects at the local level. There is no question about that. It has been one of the impetuses behind New York City taking action to start reducing pesticide use, particularly in city owned buildings including city owned apartment buildings. But the research that we are doing here, the results of that research are also clearly have clear implications for regulatory actions that the USEPA is initiating at the federal level and globally as well. The pesticides that we have been studying are widely used in the US, widely used internationally.
Interviewer: I think many of us associate pesticide use with farms, in gardens, or places like that. What are pesticides used for in a city environment?
ROBIN: People do think of pesticides as agricultural only but that is just not at all accurate. About ten percent of pesticide use in the United States is used in and around the home. There are all different types of classes of pesticides. We are interested, particularly, in the insecticides, which are the compounds that are used to kill insects. There are a lot of other types of pesticides. They are all used in and around the home. This is an issue in New York City, as it is in other cities, where there are a lot of cockroach problems. What really got us interested in the children’s center was a study that was done in 1997 that showed that more gallons of specific types of pesticides were used in Manhattan than any other place in New York State including in the agricultural communities.
Interviewer: There must be varied toxicities of insecticides.
ROBIN: The tentative toxicology is that it is the dose that makes the poison. Pesticides are designed to be toxic; they are designed to kill. And a lot of them can kill humans through the same mechanisms that they kill insects. It’s just that the dose has to be lots, lots higher. So you give tiny doses around insects and what you want to be assured of t is that that dose is below ones that would be causing any problems in humans. And that is what we have been looking at.
Interviewer: Where do you conduct your research?
ROBIN: Our research is called a community based research project, which means that we involve the community. We have involved the community from the beginning in every part of the research project. One thing that we are committed to and that our community partners have really insisted on is that if we find any evidence of harm among the women in this study that we immediately let the women know both about that and more importantly, what they can do personally to try to protect themselves. And there are things that people can do. There are always things people can do.
Interviewer: Could you explain how you compare different pairs of mothers and children who are not necessarily alike?
ROBIN: The way we are looking at this within the cohort is that we are comparing exposures across the cohort. That is not easy to do; you need to get a measure of exposure that you feel is a very reliable measure of exposure and that is why I was saying we are using fairly sophisticated techniques. What we are doing is measuring insecticide in the mother’s blood at birth and in the baby’s blood at birth. We are using the amount of the insecticide in the baby’s blood as the way of determining how much exposure that baby had. And there is a lot of variability across the cohort. There are babies with high exposures and babies with much lower exposures. We only saw these effects with the babies that had really the highest exposures. There are always problems with trying to control for other possible factors that may be compounding the relationship—may actually be what is causing the relationship. That is always a big issue. You have to spend a lot of time working on your models to convince yourself that you really have controlled for everything. These types of analyses can take years. These are done in what are called multiple regression models. They are models that contain lots and lots of other variables that we think might be compounding that relationship – maternal age, environmental tobacco smoke, lead, other possible exposures. Quality of the home environment is very important—how well the mother interacts with the child, how much stimulus there is in the home. You have to take all that into consideration when you are doing these modelings to make sure that the effects you are seeing are in fact due to the contaminant you are measuring.
Interviewer: How can we control pests without using pesticides?
ROBIN: When we found this data in this cohort—when we realized that in fact there was this much exposure and that it was damaging to the baby, at least some of these compounds were, or certainly could have been—we started doing a lot of work on ways that women in our own cohort and in the study area and this whole area in general could start controlling their pests without using these spray pesticides, which are what you are really concerned about because they release the stuff right into the air and then it is easy to get exposed to that. We have done a lot of work on that and we have just published a study on it but it does appear that there are a number of alternative ways of controlling pests and that is using a combination of trying to make your home as inhospitable to the pest as possible. That sounds like it might be difficult but it isn’t that difficult. What you try to do is make sure there is no food and there is no water left out in the open. It really is that simple. People can do that by very simple techniques—only eating in one room, not having people eat all over the apartment, cleaning up spills after the meal, taking garbage out at night, getting the landlord to repair water leaks. We found that when we would go into apartments and do those types of repairs, we were able to reduce the pest populations. Then we recommended that if you do need to use some kind of pest control measures, use the gels and the baits because they are not a spray. You are not spraying them directly into the air. You are going to get less exposure.
Interviewer: Why are gels and baits better to use?
ROBIN: They don’t volatilize. You obviously don’t want to have a child get into a pesticide measure of any kind. You don’t want to have a child get into the gels. You don’t want to have a child get into the baits. You want to use whatever you are using cautiously. But where you are more likely to get into problems is when you are actually spraying and particularly the pesticides that tend to be fairly volatile because they just volatilize into the air. When we first started using pesticides in the ‘60s and ‘70’s, the initial classes of pesticides tended to be very persistent. As a matter of fact, they have been banned for thirty years and we still detect them in most apartments. I mean they really stick around. They were replaced by these newer pesticides that are considered non-persistent and the reason for that is that they break down outside very rapidly with just light, water but they are much more persistent indoors. We are finding that this one pesticide that has been banned during the time of the study— we still detect it in every single air sample even three and four years after the ban. So it is there. It gets in the environment and it is hard to get out of the indoor environment. So it is best to try to use these other techniques. It may be that you are being overly cautious and that there aren’t health effects but if you can control your pests as well by using these techniques, it is just prudent to try to do so.
Interviewer: Why are aerosols so ubiquitous, is it a cost issue?
ROBIN: I think typically the way pesticides have been sold in spray cans and exterminators have used spray can is because the gels and baits tend to be a little bit more expensive. But there has been a change in New York City, in part being driven by this law that New York City just passed that is banning the use of these spray pesticides in city owned buildings. Also we have been finding that exterminators are much more likely now to be putting down gels and baits. That wasn’t the case when we first started this study in 1998. So there is a shift.
Interviewer: Is that directly related to your work?
ROBIN: Certainly the bill that was passed by New York City, our research findings were one of the impetuses behind that passage of that legislation. I think that is fair to say.
Interviewer: Can you tell us what you mean by “volatile”?
ROBIN: Some of the pesticides are very volatile and that means when you spray, it comes out as an aerosol. That aerosol volatilizes into the air and it will spread out. They are called semi-volatile insecticides. A lot of the insecticides that have been used in the United States are semi-volatile. Those get into the air. They spread out through the apartment. What then seems to happen is that they settle down and get into the cushions of things, caught in there, and then as people sit on them, they re-volatilize off of them and they can appear to be able to stay in the apartment for a long period of time that way. There are other pesticides, pyrethroids, that come in sprays and are not semi-volatile. These are being used more now. They are not as volatile and it may well be that there is therefore less exposure to those compounds than to these semi-volatile pesticides.
Interviewer: If you spray a non-volatile, it comes out, acts on the localized area…
ROBIN: And it settles out. It doesn’t stay in the air so you are not going to be breathing it. That is true of these pyrethroid insecticides. However, they do then settle into the dust and on the furniture and they can remain in the apartment for a long time bound to dust. You won’t get exposures from breathing them but if you have a child crawling on the floor who is eating dust, they can certainly get exposed that way. Pyrethroids have been detected in homes all over across the country in dust samples. The fact that a pesticide is in the home doesn’t necessarily mean it is causing harm. People have to realize that. And that is exactly what we are studying where so far it does indicate that this one insecticide, chloropyrofos, may have been causing harm to the developing fetus and we are looking at the other insecticides now as well, but while I say it is prudent to reduce exposures, particularly during pregnancy, I am not saying that those exposures are harmful. I just don’t know that they are not harmful, so if you can reduce your exposures, reduce them.
Interviewer: Are there still pesticides that you can buy that really shouldn’t be available?
ROBIN: There are illegal pesticides. In our area here in Washington Heights, we know that there is use of these illegal street pesticides and that is very concerning. That is probably not the case in a lot of other communities but it is the case here. These are compounds that are sold on the street. They are sold completely illegally. They are sold without any instructions. There are two of them that are used a lot. One is called Tres Pasos because it means three little steps. It is used for rodent control; mice take three little steps and drop dead. The trouble is that it is a very toxic compound that is not legal to use indoors. This is a compound that you do not want children to get a hold of at all. It would be very dangerous. The other one is pyrethroid again. It is being sold on the streets literally with no instructions for use, just comes in a powder. No instructions about how it should be mixed, how much should be used. No warnings to keep children away from it. So this is a problem in this area.
Interviewer: Many people are exposed to multiple chemicals – multiple drugs for example, which have been thoroughly tested on their own but not their interactions. Is that a concern?
ROBIN: I just served on a National Academies of Sciences Committee that did a study looking at the fact that so many Americans now have low levels of many, many, many different compounds in their blood, which we know is the case from studies the Center for Disease Control has been doing. So we are simultaneously exposed to lots and lots of different compounds at these incredibly low levels and nobody knows whether that is a problem or not. We really don’t know. But one of the issues that was then raised in that committee was the question of what are the effects of mixtures, because these are really mixtures of exposures. We are not exposed to single compounds. We are exposed to mixtures and it is a very difficult thing to study. Nobody really knows how to study it but it needs work. There is no question about it.
Interviewer: Tell us about how your study was designed.
ROBIN: Your ideal study design is that you have people who are exposed and who are not exposed to the compound you are interested in, and who are identical in all other ways. Now, obviously that doesn’t happen and so we thought a lot about this when we were designing this study. First of all, there aren’t groups that don’t have exposures to these compounds and second, you want to have the groups that you are studying to be very, very similar in other ways. So, after thinking about it a whole lot, we realized we were really best off studying it in the same community because everybody in that community was going to be similar to each other but the exposures across the community varied. We have some people in the community who have very low level exposures and other people who have higher level exposures. But they are similar in a lot of other ways because they live in the same community, they are same race, ethnicity, they come from the same background, they have a similar level of income. And then we thought very long and very hard about any possible factor that might be a confounder. Something is only a confounder if it is associated or varies with both the exposure you are interested in and the outcome. It has to vary with both at the same time otherwise it is not a confounder. So you have to think about something that could vary both with whatever exposure you are interested in, and we are looking at a lot, insecticides being one, and also with the outcome that you are interested in. You just go through every possible thing you can think of and then once you have got that long, long list, you figure out well, how am I going to gather the information about it. What is the best technique to gather the information about every single factor here on this list and you do it all different types of ways. You do it by measuring other things in the blood. You do it by going in the home and finding out a lot more about things that are going on in the home and you look at a whole range of possible indicators.
Interviewer: Can you give us an example of what a confounder is?
ROBIN: A confounder is something that varies with both your exposure and with your outcome. That is the definition of a confounder. It is probably easier to explain it with an example. A while ago somebody did a study and they found that women who breast fed longer were less likely to get breast cancer. That was the finding of the study but that wasn’t at all what was correct. Women who had babies earlier in life were less likely to get breast cancer. What happened is that the women who had babies earlier were more likely to have more babies and if they were breast feeding, they were, therefore, more likely to have cumulative years of breast feeding. So, breast feeding was a confounder of the true relationship between early age at first pregnancy and lower breast cancer risk. As soon as you put in early age of first pregnancy, the relationship with breast feeding disappeared entirely. It had nothing to do with breast feeding. That is a perfect example of a confounder in a study.
Interviewer: Sometimes you might look for the results that give you the answer that you are expecting?
ROBIN: As a scientist, as a good scientist, what you do is you try to make the finding go away as hard as you can. You think about every possible thing that might be confounding it and you put them in the model and you try to get the finding to go away and you start to believe it when you can’t get the finding to go away after a lot of work. And when we do these models, we will work on them for a year, just the model and doing that. Then you really have to convince yourself and you want to convince yourself before you publish the data.
Interviewer: Is genetic make up related to how people are affected by poisons?
ROBIN: Health and disease are complex. If a disease is going to occur, it is the result of interactions between a whole lot of different factors in any one individual, including factors that make them more susceptible to the exposures or make them less susceptible to the exposures. We know that from cigarette smoking. Somebody can smoke a cigarette for forty years and other than having smelly breath, doesn’t really seem to have any adverse effects and the next person smokes a cigarette for a year and gets lung cancer. One person was much more susceptible to the cigarettes than the other. All kinds of things can cause people to have greater susceptibility or less susceptibility, including a lot of things within our genetic makeup. People can vary about how much gets into the body. Once the compounds are in the body, people vary about how well they can get it out of the body. If the chemical causes a toxic effect in the body, people vary by how well they are able to repair that toxic effect. There are lots and lots of things in the genetic makeup of any individual that determines whether or not they are going to have any effect from any given exposure.
Interviewer: While we have been here, we have had a lot of discussion on biomarkers. Can you give us a simple explanation of biomarkers?
ROBIN: Biomarkers is a very simple concept. You can get information about exposure by asking questions. If I asked you how many cigarettes did you smoke in the last week, you can probably tell me. If I asked you how much chloropyrofos were you exposed to last week, you probably don’t have any idea, probably don’t even know what it is. But if I take a blood sample and I measure it in your blood, I know how much exposure you had. That measurement in the blood is a biomarker or a biologic marker. What it means is that rather than asking you about your exposures, I am measuring the exposure or the effect of the exposure in your body and that is a biomarker.
Interviewer: How have pesticide levels changed?
ROBIN: We are able to look at changing levels over time because we have been measuring these levels now since 1998 and have a lot of data about what levels have stayed the same and what levels have gone down. One of the things this study has clearly shown is that regulatory action works. As I mentioned this one pesticide was banned for the residential use in the middle of the study and we were able to document absolutely that that ban was very effective at reducing exposures; exposures have dropped about five fold since that ban until now. We are still finding it in most homes but at much lower levels. The other thing that this study showed is that once that ban had taken effect, the health effects that we were seeing among the babies before the ban, we weren’t seeing after the ban. So that was very nice, very nice data that showed you can address these problems. If you identify a problem, you can address the problem. And we have seen that with other things as well. Lead is a beautiful example.
There were a number of studies that looked at health effects of lead on young children and when those studies clearly showed that there was a reduced I.Q. in these children as a result of lead exposure, that information resulted in the banning of lead from gasoline in the United States and the blood lead levels of people in the United States dropped absolutely dramatically. It is wonderful success story. We have seen the same thing with cigarette smoking with the concern over environmental tobacco smoke. The educational campaigns about smoking and about environmental tobacco smoke in the United States have been tremendously successful. And again, measuring these levels in the bodies of people in the United States has shown a dramatic drop in exposures to cigarettes. It is one of the reasons I don’t get depressed, because if you can show these things, you can take action to prevent them.
Interviewer: Looking to the future, there are many concerns because we use so many different chemicals. Do you have any positive predictions?
ROBIN: There is a lot of exposure out there and we are introducing new chemicals all the time. A lot of them come onto the market with what I would call adequate testing. I hope we can learn from the failures of the past and address this. I am not sure that we are learning but it is certainly my fervent hope that we will. But my sense is all any of us can do is do our best and go forward positively, each one of us in our own way helping as we can, and we will see where that leads. Yes, I am a positive person. I have seen a lot of successes. I don’t see why we can’t keep making these successes.
6.1 Risk, Exposure, and Health Video
We all require food, air, and water to survive — which are contaminated to some extent by man-made pollutants. Two studies, one in a rural western mining town and another in a dense urban population, reveal how these exposures impact health, and what can be done to reduce the risks.
Unit 1 Many Planets, One Earth
Astronomers have discovered dozens of planets orbiting other stars, and space probes have explored many parts of our solar system, but so far scientists have only discovered one place in the universe where conditions are suitable for complex life forms: Earth. In this unit, examine the unique characteristics that make our planet habitable and learn how these conditions were created.
unit 2 Atmosphere
The atmosphere is what makes the Earth habitable. Heat-trapping gases allow ecosystems to flourish. While the NOAA Global Monitoring Project documents the fluctuations in greenhouse gases worldwide, MIT's Kerry Emanuel looks at the role of hurricanes in regulating global climate.
Unit 3 Oceans
Oceans cover three-quarters of the Earth's surface, but many parts of the deep oceans have yet to be explored. Learn about the large-scale ocean circulation patterns that help to regulate temperatures and weather patterns on land, and the microscopic marine organisms that form the base of marine food webs.
Unit 4 Ecosystems
Why are there so many living organisms on Earth, and so many different species? How do the characteristics of the nonliving environment, such as soil quality and water salinity, help determine which organisms thrive in particular areas? These questions are central to the study of ecosystems—communities of living organisms in particular places and the chemical and physical factors that influence them. Learn how scientists study ecosystems to predict how they may change over time and respond to human impacts.
Unit 5 Human Population Dynamics
What factors influence human population growth trends most strongly, and how does population growth or decline impact the environment? Does urbanization threaten our quality of life or offer a pathway to better living conditions? What are the social implications of an aging world population? Discover how demographers approach these questions through the study of human population dynamics.
Unit 6 Risk, Exposure, and Health
We are exposed to numerous chemicals every day from environmental sources such as air and water pollution, pesticides, cleaning products, and food additives. Some of these chemicals are threats to human health, but tracing exposures and determining what levels of risk they pose is a painstaking process. How do harmful substances enter the body, and how do they damage cells? Learn how dangers are assessed, what kind of regulations we use to reduce exposures, and how we manage associated human health risks.
Unit 7 Agriculture
Demographers project that Earth's population will peak during the 21st century at approximately ten billion people. But the amount of new cultivable land that can be brought under production is limited. In many nations, the need to feed a growing population is spurring an intensification of agriculture—finding ways to grow higher yields of food, fuel, and fiber from a given amount of land, water, and labor. This unit describes the physical and environmental factors that limit crop growth and discusses ways of minimizing agriculture's extensive environmental impacts.
unit 8 Water Resources
Earth's water resources, including rivers, lakes, oceans, and underground aquifers, are under stress in many regions. Humans need water for drinking, sanitation, agriculture, and industry; and contaminated water can spread illnesses and disease vectors, so clean water is both an environmental and a public health issue. In this unit, learn how water is distributed around the globe; how it cycles among the oceans, atmosphere, and land; and how human activities are affecting our finite supply of usable water.
unit 9 Biodiversity Decline
Living species on Earth may number anywhere from 5 million to 50 million or more. Although we have yet to identify and describe most of these life forms, we know that many are endangered today by development, pollution, over-harvesting, and other threats. Earth has experienced mass extinctions in the past due to natural causes, but the factors reducing biodiversity today increasingly stem from human activities. In this unit we see how scientists measure biodiversity, how it benefits our species, and what trends might cause Earth's next mass extinction.
unit 10 Energy Challenges
Global energy use increases by the day. Polluting the atmosphere with ever more carbon dioxide is not a viable solution for our future energy needs. Can new technologies such as carbon sequestration and ethanol production help provide the energy we need without pushing the concentrations of CO2 to dangerous levels?
Unit 11 Atmospheric Pollution
Many forms of atmospheric pollution affect human health and the environment at levels from local to global. These contaminants are emitted from diverse sources, and some of them react together to form new compounds in the air. Industrialized nations have made important progress toward controlling some pollutants in recent decades, but air quality is much worse in many developing countries, and global circulation patterns can transport some types of pollution rapidly around the world. In this unit, discover the basic chemistry of atmospheric pollution and learn which human activities have the greatest impacts on air quality.
Unit 12 Earth’s Changing Climate
Earth's climate is a sensitive system that is subject to dramatic shifts over varying time scales. Today human activities are altering the climate system by increasing concentrations of heat-trapping greenhouse gases in the atmosphere, which raises global temperatures. In this unit, examine the science behind global climate change and explore its potential impacts on natural ecosystems and human societies.
Unit 13 Looking Forward: Our Global Experiment
Emerging technologies offer potential solutions to environmental problems. Over the long-term, human ingenuity may ensure the survival not only of our own species but of the complex ecosystems that enhance the quality of human life. In this unit, examine the wide range of efforts now underway to mitigate the worst effects of man-made environmental change, looking toward those that will have a positive impact on the future of our habitable planet.