The Habitable Planet: A Systems Approach to Environmental Science
Risk, Exposure, and Health Interview with Howard Hu
Interviewer: How did you get interested in science?
HOWARD: Well, my parents were Chinese immigrants. My father was an engineer and he pushed me towards medicine but I was much more interested in broader things about society. I grew up in the 1970s, and environmental health and occupational health came to me early on through a personal experience when I was exposed to asbestos while working in a shipyard. I knew from that experience that I was at increased risk for lung cancer and a disease that would shrink my lungs. When I found out that asbestos was something that had been regulated for years but poorly enforced, allowing me to be exposed, I realized that I had stumbled upon a field that was at the intersection of health, politics, social economics. And it was very interesting to me.
Interviewer: How is your health now due to the asbestos exposure?
HOWARD: Oh, I’m not about to keel over. I’m okay. But, I do have to get checked out and have a chest X-ray every three to five years.
Interviewer: What is the fundamental research question that you and your team are working on at Tar Creek?
HOWARD: The fundamental research question we’re addressing at the Tar Creek Superfund Site is, “What are the health effects of mixtures of metals, in this case, the mixtures of lead, manganese, cadmium, and arsenic that exist in mining waste?”
Interviewer: Can you explain what a Superfund site is?
HOWARD: A Superfund site, in general, is one that has been designated a high priority area of contamination by the Environmental Protection Agency (EPA). They keep this list, called the National Priority List, which I believe has over two thousand sites. The sites are rated based on the number of contaminants, how toxic they are, and the potential for human exposure.
Interviewer: Tar Creek was one of the earliest listings, and one of the most extreme?
HOWARD: That’s correct. This was one of the first sites that was so designated on the National Priority List, because of its size and the immediate recognition that metals exposure was a hazard.
Interviewer: How did you get involved with the research at Tar Creek?
HOWARD: The story really goes back about twelve years or so. This is an area of the country where metals have been mined for many decades. And people have been living amidst these mountains of mining waste during that time without a good idea of how it was affecting their health. In the 1970s this was one of the areas that was designated as a Superfund site because of the recognition that the exposure to metals must be relevant. But no health studies had been done.
In the mid 1990s, a woman named Rebecca Jim, who’s the head of a community agency called Local Environmental Action Demanded (I love that acronym, LEAD), contacted me after reading about some of our research and asked me whether I could be interested in their exposures, and whether I could measure some of the teeth that she had collected from school aged children for lead. She had read some of our research which indicated that tooth lead levels provide a metric for understanding how much lead exposure a child had endured during the first few years of life. We measured those teeth. The levels were relatively high. And, that began a relationship in which she encouraged us to come to the Tar Creek Superfund Site and try to shed some light on what the health impacts of the mining waste were in this community.
Around 2001, we began to do some research with support from the Harvard Superfund Basic Research Program. And, then in 2004, we got a major grant from the National Institute of Environmental Health Sciences and the Environmental Protection Agency to make this the focal point of our human population work stemming from our Center for Children’s Environmental Health and Disease Prevention Research.
Interviewer: When I went to visit Tar Creek, there was mention of research being done on aquifers.
HOWARD: The research on the aquifers has mostly been conducted by the United States Geological Survey. We have used that research to provide a preliminary assessment of what the metals exposure might be in the residents. Our research is much more focused on the immediate environment of the residents living in the Tar Creek Superfund Site, trying to understand what their exposures might be from house dust, soil, air, drinking water, food, so that we have a better idea of how these metals may travel from these mining sites and from these aquifers to the actual people themselves.
Interviewer: What are the big questions at the base of your research, and how does it fit in with the bigger picture of general health and the work you’re doing here as well?
HOWARD: In terms of the big picture, environmental health as a science has become increasingly sophisticated over these years and now we have very good ideas based on basic research in the laboratory and human population studies of what individual toxicants can do to people, whether it’s asbestos, or benzene, or lead.
One of the big questions that we’re trying to get at, however, is how mixtures of toxicants, in this case metals, may affect human health. And, there is good evidence from basic research work that you cannot predict what the ultimate human health impacts might be from simply knowing what the individual toxicants can do. Mixtures can, in the most extreme cases, interact in ways that are unforeseen and give you toxic ramifications that are much greater than what could be predicted from the single exposures. On the other hand, in some mixtures, toxicants can cancel out the effects of each other. So this research, which is a combination of human population studies and basic science studies in the laboratory, is trying to attack this problem using a well-integrated systematic approach of studies to understand the health effects of mixtures.
Interviewer: How do you break down such a big question into research topics? What are you actually studying right now that contributes to answering the “big question”?
HOWARD: The big picture question that we’re looking at is, “What are the health effects of mixtures of metals?” This is a question that can be broken down into how these mixtures of metals move from these mining waste sites into the immediate vicinity of people with potential for exposure in drinking water, and food, and air. Then it can be broken down into how these things might interact inside the gut, or in the lungs, or in the brain, to eventually cause toxicity.
This particular set of studies is focusing on early life, probably because pregnancy and the first two years of life are generally recognized as being extremely vulnerable periods to toxicants, particularly neurologically – brain affecting – toxicants.
Interviewer: Can you explain the different projects involved in this study?
HOWARD: There are actually five major projects in our package of studies. Three of them are human population studies. I’ll describe those first. One of them is known as a birth cohort study. We’re actually recruiting women who are giving birth at a local hospital and measuring the levels of metals that appear in the umbilical cord blood, in mom’s hair, and in the infants as they develop. And then we follow those infants and try to understand how those metal exposures may impact neurodevelopment. The second human population study is looking at how these mothers are actually exposed to metals by looking at what’s in their air, what’s in their food, what’s in their drinking water, what’s in their house dust. The house dust also is important for the babies as they grow up, because hand to mouth behavior in babies is normal. And they are always exposed to house dust. The third human population study is looking at the general environment of where the Tar Creek residents live and looking at how the metals might travel from the chat piles – these large mountains of mining waste – into the drinking water, into the soil, and into the road where the waste that gets churned up by activities like cars driving through creates dust that people can breathe.
Interviewer: What are some of the previous findings that indicate the need to learn more about the Tar Creek area?
HOWARD: Some of the previous work that has led us to focus on the Tar Creek Superfund Site, including samples by the Environmental Protection Agency and the Geological Survey of the Federal Government, indicate high levels of metals throughout the entire Tar Creek Superfund area. There have also been some exposure studies involving biological samples, such as the Tribal Efforts Against Lead Study, conducted by researchers from the University of Oklahoma, that showed elevated levels of lead in children aged two and three years.
Interviewer: Can you tell me bit about the types of warning signs a community must experience in order to take the health hazards of mining seriously? Is it the health issues that catalyze action, or something else?
HOWARD: The issue of mining and a community’s health is very complex. We have focused on the issue of metals exposure and its impact on development. It’s a subtle issue. If metals actually lower your child’s I.Q. by five points or ten points, it’s not something you’re ever going to recognize. But it’s something obviously that will be hugely important for parents as well as the children. That’s subtle. And it doesn’t surprise me that residents in a toxic site where there might be severe implications may not have that as a front burner issue for them because it’s hard to see. On the other hand, mining also involves physical hazards, such as the collapse of ground under houses, under roads, because of unregistered mining sites and what are called cave-ins. Those are more obvious physical threats that bring these issues immediately to the forefront, to the public. They’re linked, of course, because these are all related to mining. One has to bring all issues to the forefront to a community, and they have to be done in a linked way so that the community can really understand in a holistic way how mining might be a threat to their health.
Interviewer: Can you describe some of the studies conducted in a lab that complement the studies of human populations?
HOWARD: This Center involves basic science studies performed in the laboratory that are integrated with our human population studies. One of these studies involves taking actual chat mining waste and exposing animals, in this case mice and rats, and trying to see how the metals interact with each other and how the animals absorb the effect – their absorption in the gut, or in the nose, or in the lungs. Among the early findings that we have uncovered in this research is that, in fact, respiratory exposure and nasal exposure may be an extremely relevant route of exposure for manganese, a metal that’s well known to be a neurotoxin. Part of that is related to the fact that olfaction, that is the sense of smell, involves a nerve that goes directly from the brain to the sinuses. And manganese can actually be absorbed right through the sinus into that nerve and transport it directly to the brain, without ever having to be absorbed into blood. This is one of the surprising findings that may explain some of the most relevant neurotoxin potential for a metal like manganese.
Another of our animal studies is looking at neurotoxicity in a more direct manner by injecting or exposing these animals to mixtures of metals and looking at neurobehavioral outcomes, such as the ability of these animals to remember, to sustain life through stresses, and their ability to do specific tasks involving coordination. All of these kinds of studies will go a long way to helping us understand how these mixtures of metals may affect neurodevelopment in children.
Interviewer: How long have you been doing animal studies and what are your findings so far?
HOWARD: For almost two years. One of the studies has told us that the sinus and nasal route of absorption might be extremely relevant. Another of the studies tells us that manganese may be more toxic than we thought and may interact with arsenic to increase its impact on child development.
Interviewer: Are the levels of human exposure to hazardous metals (or metal mixtures) going up, down, or staying the same?
HOWARD: It’s a very mixed, moving picture in which we only have small pieces of the puzzle. It’s too early to understand whether the overall trend for human exposure is going up, going down, or flat. We simply don’t have that data yet.
Interviewer: Will you or do you study what happens to the people who deal directly with the mining waste?
HOWARD: We’d like to be able to do that. Right now we’re focusing on the mother/infant pairs and their exposures. But it will also be important to see whether the workers who are using the mining waste, as you mentioned, and are shoveling it out of trucks, and who are there when it’s being pulverized into dust are significantly exposed. And we would like to know whether the secondary use, trucking it to other parts, of the country may eventually result in significant exposures. We simply don’t know.
Interviewer: How does weathering affect the risk of exposure?
HOWARD: One of the potentially helpful effects of weathering may be to develop crusts that will keep down the level of dust in respirable particles. Weathering may also produce the actual waste that’s in the immediate environment by getting it further down into soil, where it’s less available for human exposure.
Interviewer: Regarding Tar Creek, do you have any gut feeling about what the future holds?
HOWARD: I don’t anticipate that there are going to be major changes over decades. There will be subtle changes as the years go by. I think that some of the movement of the residents may address some of the questions of human exposure. But certainly not all of them, given the multiple sites that are impacted in this Superfund area as well as the use of this chat all over the state.
Interviewer: The WHO (World Health Organization) publishes acceptable exposure levels, but your studies have found that exposure levels below the WHO standard may still have neurological effects, among other things. Can you compare your findings with global findings, or will your studies affect WHO levels?
HOWARD: Well, again, our study is focused on the big picture issue of how mixtures may impact human health. This is not an issue that WHO has considered in setting its standards, or, for that matter, the United States Centers for Disease Control. So it could be considered as a cutting edge issue in environmental health. The exposures information that we have so far in the children being born is somewhat encouraging, showing that the exposures aren’t quite as high as they had been measured perhaps ten or fifteen years ago. We don’t know yet why that might be true, or whether it’s true for all children in this area. But we’re certainly hopeful that the residents, as they gain more knowledge of these exposures, their potential effects, and how to avoid them, may be actually reducing their own exposures through simple common sense measures, some of which we are already beginning to promote as measures people can take. And that’s maybe why we’re seeing a reduction over time.
Interviewer: Can you briefly mention how your project ties into the larger world?
HOWARD: The world implications of the subjects that we’re studying include the fact that metals are now recognized as being more diverse in their ability to affect our health than had been known before. For instance, manganese and arsenic, which are metals that, in the past we knew were toxic at high levels to adults, are now seen as potential threats to child development, something that has not been appreciated before. Arsenic is also something that is a risk for neurodevelopmental toxicity, not just cancer. And, that’s a new revelation for metals.
Mining is a process that occurs all over the world, in this country, in developed countries, and in a developing world, at an increasing pace as industrialization fuels the need for all these metals in mega quantities for manufacturing. That means that what we’re discovering will have implications for communities all over the world who are exposed to this metal mining waste.
Interviewer: What are some of the uses for the metals that were mined at the Tar Creek mining area?
HOWARD: The Tar Creek mining area was a source of metals for our nation’s industries and our armaments for many decades. A lot of the ammunition that was used in World War Two, in fact, had its origins in metal mines of Tar Creek.
Interviewer: Other than educating the public, as you said, are there any other things we can do to mitigate the hazards of the mine waste?
HOWARD: I am hopeful that our research will allow us to better target interventions for people, including those who are living in the worst areas of mining waste. Among the interventions may be nutritional interventions emphasizing various nutrients that may decrease absorption of toxic metals that may mitigate the ultimate toxic affects. Avoidance of some lifestyles, whether it’s food sources or behaviors that will increase exposure. And, if necessary, drug treatments that can reduce metal levels in the body or at key target organs to improve outcomes. Those are all possible interventions in an area where the exposures are extreme or inevitable. Public health measures or sociologic measures, like moving people, of course, are another drastic measure that have to considered, and are being considered at the Tar Creek Superfund Site.
Interviewer: So, can you concisely sum up and describe the health component of what you are studying at the Tar Creek Superfund Site?
HOWARD: The health component of what we’re focusing on at the Tar Creek Superfund Site is child development, specifically neurodevelopment. How well can these children think and perform as they get into school age? What is their I.Q.? What is their coordination? What is their ability to think abstractly? Those are all key skills that our children need, particularly since today’s world is a knowledge-based economy. They have to be able to think well. That is not the only health implication that has to be considered over time. Adults are also at risk. Our particular research group has other research projects which have shown that metals exposure may ultimately result in adults in hypertension, heart attacks, accelerated declines in thinking ability, Alzheimer’s, Parkinson’s Disease. And, finally, there’s the recognition that children’s exposures may actually manifest themselves as adult disease later in life. That’s called the fetal origins of adult disease hypothesis, a very important theory that may have currency in today’s world.
Interviewer: How old are the children you have been studying? I visited with the principal of the school and she claims that she sees the effects in her students, but has any study been done on those students?
HOWARD: Not yet. At this point, we’re following the mother/infant pairs who were initially enrolled in our study. And the oldest children are only around three years old or so. Our eventual goal is to try to follow them as they get into school and understand how their exposures may impact behaviors that every parent/teacher knows.
Interviewer: Can you comment on what the implications are of relocating a lot of the hazardous mining to places outside the US?
HOWARD: I think the issue of something like mining metals has become a global issue. It is an issue of economics, not just politics. In environmental health we call this the exportation of hazardous wastes, products, and industries. And mining is one of those industries that has moved offshore. Nowadays, a lot of the metals that we enjoy in our products, in our country, stem from mines that are in Indonesia, Malaysia, India, Africa, and we do have to think about how these communities that live around these mining sites are affected. Eventually, it all gets down to the globalization of the world’s economies and, our interdependence in not only commerce, but people. We will eventually be affected if the communities around mines in South Africa, or Malaysia, are poisoned by these wastes, not only through the court systems, but also through civil unrest, by other injunctions and protests, and people who understand that fundamentally the world is responsible for the health of people when our economies are this interdependent. That’s part of the implications of what we’re doing with mining waste research.
Interviewer: Are there other types of mines, different from the Tar Creek mines that cause health hazards?
HOWARD: Yes. The issue of mining and health extends far beyond the kinds of mines that we’re studying. Mines that are focused on gold actually use mercury, which has been imported as part of the purification process, and that has led to extreme contamination in some environments, like in Brazil. Mining for uranium, which is huge for nuclear fuel, involves uranium tailings that are a huge radiation threat to populations living around mines. So there are complicated issues that are specific for the substance that’s being mined and the eventual risks that the communities surrounding those mines are exposed to.
Interviewer: There’s still quite a bit of copper being mined in this state (OK). Is that process a bit cleaner than that of some other minerals that are being mined, or does that also have other kinds of hazards?
HOWARD: Copper mining also involves a number of different threats, including collateral exposures to arsenic and lead, and through the smelting process, the purification process, exposure to those metals affects communities surrounding the smelter.
Interviewer: Can you explain what the collateral damages are?
HOWARD: A big issue with mines is exposure not only to the metal that’s being mined, but collateral exposure and health affects from the other metals that derive from the ore that produces the metal of interest. So, for instance, the mining of copper will inevitably involve potential exposure to lead and arsenic. And the mining of gold will not only involve exposure to other metals and ores, but exposure to mercury, which is specifically imported for the purification process and then often discarded as waste.
So this discussion of the multiplicity of metals at each of these mining sites, from the mine, including the metals of interests and the collateral metals that are produced, to the metals that are brought in for the purification process, means that the issue of mixtures of metals is germane all over the world. That’s exactly the kind of issue that we’re trying to understand at the Tar Creek Superfund Site.
Interviewer: What are the implications of your studies and how do you hope they affect the future?
HOWARD: The big implications of the kind of work that we’re doing is number one, to demonstrate exactly what threats ensue from development and the industries that we employ to give us the products we need to live. Because a lot of these exposures are now occurring at their greatest in the developing world, one of my great hopes is that the developing world will be able to use this information during the development process, to leapfrog some of the worst excesses of our own society and go straight to a cleaner technology, a cleaner developmental model, that will allow their populations to reduce or prevent these exposures from happening from the beginning.
Interviewer: Can you discuss the costs of mining and how that ties in to public health?
HOWARD: The question of economics and how much these products cost is a very relevant one. And what it really means is that we have underestimated what the costs are. The human costs are for the environmental health threats that are produced when we mine these metals. In the future what we really need to do is to get a whole product life cycle cost when we embark on the next adventure to mine the next metal. Because that cost will allow us to recognize that preventing exposure by implementing, at the outset, a cleaner technology for mining metals or for making the next plastic will allow us to avoid the human cost down the line to defective communities, or the users of the products at the end.
Interviewer: Is there anything else you care to mention?
HOWARD: Yes, I guess there is an issue I should cover. There’s another aspect to our research, which is a very important dimension to environmental health. That is understanding the genetic variation in children and how some children might be genetically susceptible to the health effects of metals. We call that gene environment interaction. Nowadays, environmental health scientists recognize that most diseases are a complex interplay between our genes and our environment. We no longer think of disease as being either genes or environment. We’re also trying to understand that at the Tar Creek Superfund Site as part of our package of research.
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.