A bike ride a day…. might not keep the doctor away?

An abbreviated version of this post was originally published in The Crosscut with the title “Is biking a Catch-22 situation?

My friends think that I’m slightly obsessed. I prefer to think of myself as extremely passionate.

I’m getting my PhD in toxicology, but my interests don’t stop when I leave campus. I live and breathe this stuff: I love reading, learning, and writing about all things environmental health.

So, naturally, I’m worried about my own exposures to the overwhelming number of pollutants that we’re surrounded by. Though much is out of my control, I do what I can to minimize my exposures by buying organic (even on a student budget, and sometimes to an extreme that annoys my friends and family), avoiding processed and packaged foods, minimizing my use of plastics, choosing fragrance-free products, obsessively searching for flameretardant free furniture, etc. The list goes on. My environmental health knowledge and concern for my health (as well as the health of my potential future children?) drive my lifestyle and purchasing decisions.

Yet, there’s one lifestyle choice that I’m not willing to give up, especially while living in Seattle: biking. I bike commute to school almost every day of the year. (I only missed 2 days this winter, when the roads were icy). I love riding to campus; it’s my morning and evening meditation/reflection time and my exercise.

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Heading home from school on my bike. Photo credit: Alex Kritchevsky

While I do ride on the BurkeGilman trail for most of the way, with gorgeous views of the water, mountains and city skyline, there are also several segments on roads. Obviously, biking on busy, car-filled streets presents immediate physical dangers, like car-bike collisions (my housemate has been hit twice in 6 months) and getting doored (ouch! Looks so painful). But, there’s also all that disgusting air pollution I inhale as take deep breaths alongside the ever-steady stream of cars. Luckily, at least for now, I’m not affected by asthma or other respiratory conditions. Yet, air pollution has been linked to many health problems, including cardiovascular disease and dementia (the latter is the subject of my PhD dissertation); I can’t help but think about those dangers on my daily rides.

Am I causing more harm than good to myself by commuting by bike? Why am I willing to impose such strict controls on other parts of my life (ie: purchasing decisions), but I allow myself to take deep breaths of noxious miasma every single day? Sure, exercise is good for me – for both my physical health and my brain health. But, do the negatives (pollution, collisions) outweigh the positives (physical and emotional health)?

What am I exposed to?

The short answer is: a toxic brew of traffic-related air pollution, at higher levels when biking on busier roads, and probably in higher doses than while driving in a car.

This report (prepared for the National Institute for Transportation and Communities) has a good summary of the research (as of 2014) about traffic-related air pollution exposure to bicyclists. Since then, more studies (for example, in Salt Lake City, Utah; Minneapolis, Minnesota; and Montreal, Canada (here and here)) have also quantified exposures to city cyclists; others (like this one in New York City) are in process now. All of these assessments are specific to each city, season, time, and route. It will take much more research to develop a body of information that reflects the average and range of possible exposures to cyclists.

Such research with individual level measurements is crucial. We routinely track ambient air pollution across the country with a surprisingly few number of monitors (check out this interactive map to explore your area). These devices, which are often located away from major roadways or pollution sources, would definitely underestimate my own exposure, especially when I’m biking right behind a bus.

Exact quantification pending, what am I breathing in on my morning and evening commutes?

  • Particulate matter (PM): PM is a mix of dust, dirt, and soot particles. Sources of PM (and gases that trigger formation of PM) include wood stoves, fires, power plants, vehicles, industrial facilities, and construction sites, among others. PM can also include heavy metals (such as lead, cadmium, copper, and zinc) from tires, brake wear, and diesel exhaust, as well as black carbon. Smaller particles, such as PM2.5 (≤2.5 micrometers) and ultrafine (UF) PM (≤100 nanometers), can penetrate more deeply into our bodies (and are thus likely more dangerous) than PM10 (≤10 micrometers). PM has been linked to adverse respiratory, cardiovascular, cognitive (neurodevelopmental and neurodegenerative), and reproductive outcomes.
  • Nitrogen oxides (NOx): Nitrogen oxides, reactive gases emitted from vehicles and power plants, are highly irritating to the respiratory system.
  • Volatile organic compounds (VOCs): Released from fuels and vehicle exhaust, this large class of compounds contributes to ozone formation. Many have also been classified as “hazardous air pollutants” by the US EPA because of their link to cancer, reproductive, or adverse environmental effects.
  • Ozone (O3): Ozone is formed through chemical reactions of NOx and VOCs in the presence of sunlight and triggers respiratory health effects, like reduced lung function and asthma attacks.
  • Carbon monoxide (CO): Colorless and odorless, carbon monoxide is produced through incomplete combustion from cars, trucks, and machinery. While the major concern with CO exposure at high levels indoors is its potential to interfere with transport of oxygen in the body and cause acute neurological and cardiac effects, the likely consequences of lower level outdoor exposures are more subtle effects on the heart and brain.
  • Sulfur dioxide (SO2): Sulfur dioxide is released from industrial facilities and vehicles burning fuel with high sulfur content. It is linked to respiratory problems (like asthma attacks and airway irritation) and can contribute to formation of PM.

Yuck.

Of course, we are all exposed to these air pollutants when we walk outside (and while driving in cars). But, during vigorous exercise, like biking up Seattle’s killer hills, we breathe in at 2-5x higher rates, and also more deeply, than at rest. So, I’m inhaling much more of all this bad stuff when I bike – in traffic – each day.

What are the consequences?

Research on the effects of air pollution exposure during exercise and active transportation (ie: walking and cycling) is beginning to emerge. According to one recent study, walking along busy streets reduced the short term cardiovascular benefits of the exercise compared to walking in a park. In studies of cyclists, researchers have found that biking in traffic is associated with various physiological changes, such as increases in certain inflammatory blood cells, alterations in heart rate variability (see here, here, and here) and other cardiovascular measures, and decreases in lung function. The implications of these changes are still unclear, however.  As usual, we need more research on the short- and long-term health effects of cycling in traffic.

Several studies (see selected examples from 2017, 2016, 2015, 2014, and 2010) have tried to examine the overall health trade-offs of cycling in cities. The general conclusion is that the long-term benefits of active transportation (ie: namely, physical activity) outweigh the potential risks from traffic accidents and air pollution. However, I think these assessments are limited in several ways:

  • Most focus on the impact on mortality only, rather than the other myriad of health effects from air pollution that could lead to decreased quality of life and then, indirectly, mortality.
  • Most only consider the effects of a single pollutant (usually PM2.5) rather than the effects of combined exposures to multiple traffic-related air pollutants (ie: what happens in the real world).
  • On a more technical level, they assume a linear dose-response (solid line, below), where the relationship between exposure and outcome is the same across all levels of exposure. However, some evidence suggests that this may not actually be the case for PM2.5. Instead, the curve might be supralinear (dashed line, below), where the risk increases more steeply at lower levels of exposure. In this scenario, there might be greater benefits to health per unit decrease in exposure at lower ends of the spectrum, which would alter the modeling calculations.
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Linear (solid line) vs. supralinear cure (dashed line). Image from: Goodkind, Andrew L., et al. “A Spatial Model of Air Pollution: The Impact of the Concentration-Response Function.” Journal of the Association of Environmental and Resource Economists, vol. 1, no. 4, 2014, pp. 451–479. JSTOR, JSTOR, http://www.jstor.org/stable/10.1086/678985.
  • The alternative scenario (in epidemiology speak, the “counterfactual”) used in these cost-benefit assessments is decreased physical exercise. In other words, they are roughly comparing: [exercise + pollution] vs. [no exercise + pollution]. Because the benefits of physical activity are so enormous, this equation tips towards the [exercise + pollution] side. However, if I didn’t commute by bike, I would replace this exercise with alternative activities (with less exposure to air pollution, presumably). If my equation is instead [exercise + pollution] vs. [exercise + less pollution], it would likely tip in the other direction.

So, in summary, we don’t fully understand all of the physiological impacts of biking in traffic-related air pollution, and I think that the current cost-benefit analyses may actually underestimate the long-term costs to my health.

Hmmm…. Should I re-evaluate my decision?

Decision-making

            Last summer, I bought myself an air pollution mask to wear while biking. But, while I hate to admit it, I don’t use it every day. (It often causes my sunglasses to fog up!). I really should use it – assuming it is as effective as it claims?

Even though Seattle has the reputation of having fairly good air quality, the 2018 American Lung Association State of the Air Report indicates that there is still enormous room for improvement. (And, as I noted above, this city-level ranking, based on ambient air monitors, likely definitely underestimates my exposure while biking).

Everyone makes risk-related choices differently, based on their own calculations and priorities; risk perception and decision-making is complex and not entirely rational. But, in general, people are more likely to accept risks that they perceive as controllable, familiar and natural compared to those they perceive as imposed by others, uncontrollable, and unfamiliar (see image, below).

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Risk Space & Public Perception. Morgan, M. Granger. “Risk Analysis and Management.” Scientific American, vol. 269, no. 1, 1993, pp. 32–41. JSTOR, JSTOR, http://www.jstor.org/stable/24941545.

I’m still trying to understand the calculations that led me to my decision to expose myself to substantial pollution every day. Maybe it is related to the fact that I have control in this situation, since it is my choice to bike? Maybe it is because Seattle appears to have relatively clean air, compared to other places I’ve lived, like Atlanta and Bangkok, where the pollution is more directly visible?

Maybe… maybe… I just love biking too much, and this is where I draw my personal line. While it is definitely important to me to minimize harmful exposures and prioritize my health, I cannot and do not want to live in a complete bubble (though sometimes it seems to others that I already do). Life involves risk, and I’ve somehow decided that this is one I’m willing to take. Biking every day brings me too much happiness to give up (at least for now). Plus, cars are no safe haven; there’s plenty of dirty air inside from both internal and external sources.

Consolatory actions

While I take this risk, which is perhaps ironic given my PhD research on air pollution and dementia, there are some things I can do to mitigate my exposures. In addition to wearing my mask more consistently, I can check local air quality (like through this pollution app) and avoid riding on particularly bad days (like last summer, when Seattle was choked by horrific wildfire smoke). When bike paths are not available, I can do a better job of altering my route to prioritize low traffic roads, where I will be less exposed than on busier routes.

However, like for all pollutants, individuals only have limited abilities to control their own exposures. In the end, we need systemic, societal changes to make cities safer and healthier for people: stricter controls of vehicle emissions, increased utilization of electric cars and buses, improved public transportation, better bicycling infrastructure (eg: off-street bike paths), more greenspace, etc. The intersection of urban planning and public health definitely intrigues me (my next PhD? No, just kidding).

Ultimately, I hope that my own research can demonstrate the importance of strengthening air quality regulations and help motivate policies to reduce exposures across the population.

As you can see, it’s personal now.

 

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Election Reflections: Women in Science

It goes without saying that the outcome of the recent U.S. presidential election was a shock. I will avoid a long-winded discussion of the associated consequences and just acknowledge that we came painfully close to electing the first female president of the country.

In the weeks leading up to the election, I had felt a contagious energy among my female friends – a great hope that we could have a role model in the highest office of the country.

I don’t have presidential aspirations, however. So, upon further reflection, I realized that much more important to my own growth and ambitions has been the presence of female role models in my field of environmental health sciences. Unlike for my mother, who had few women role models in her early days in public health, I feel fortunate to have numerous, highly successful female scientists to look up to. Because of these inspiring women (including my mother!), I have never doubted the possibility that I can achieve my professional goals.

Perhaps my earliest model of a female scientist and change-maker was Rachel Carson, whose pioneering environmental work I learned about during elementary school. While I probably did not understand the full scope of her impact at that young age, I was evidently motivated enough by her story to dress up as Carson during career day.

Years later, during college, I read Our Stolen Future, an eye-opening book that Al Gore has referred to as a sequel to Carson’s Silent Spring. Who better to learn from about endocrine disruption than the late Theo Colborn, co-author of this book and a visionary leader who is often called the “mother of endocrine disruption?” Reading this work provided immediate clarity and direction to my undergraduate studies. After college, as I began to further immerse myself in the world of environmental health at Environmental Defense Fund, I became increasingly inspired by the work of Colborn and the many other contemporary female scientists who are shaping the field.

Women are leading some of today’s most important science policy and advocacy efforts, and I have had the privilege to interact with several of these amazing individuals. I greatly admire Sarah Vogel (Environmental Defense Fund) Ruthann Rudel (Silent Spring Institute), Jennifer Sass (Natural Resources Defense Council), and Molly Rauch (Moms Clean Air Force), among others, for their efforts to promote the translation of strong science into health protective policies.

All science is a team effort, of course, but female scientists across the country have led many of the studies that these and other organizations draw upon in their public health work.

  • Ruthann and her team at Silent Spring Institute have conducted important and innovative work related to endocrine-active chemicals and breast cancer risk.
  • North Carolina has the preeminent Heather Duo: Heather Stapleton at Duke University, who researches routes of exposure to flame retardants, and Heather Patisaul, at North Carolina State University, who is examining the effects of chemical exposures on the neuroendocrine (brain & hormonal) system.
  • Dana Dolinoy, at the University of Michigan, is a leading expert in epigenetics (changes in how a gene is expressed rather than a change in the genetic code itself).
  • Tracey Woodruff and her team at the UCSF Program on Reproductive Health and the Environment have done extensive work in diverse areas, ranging from advancing methods for systematic review to assessing prenatal chemical exposures.
  • Frederica Perera, at Columbia University, pioneered the field of molecular epidemiology (using specific biomarkers to understand the link between environmental exposures and disease).
  • Irva Hertz-Picciotto, at the University of California, Davis is a top environmental epidemiologist with a particular focus on the environmental factors that contribute to autism. (She recently co-founded Project TEDNR, a collaborative initiative involving scientists, policy-makers, and advocates that aims to reduce exposures to neurotoxicants.)

I could go on and on (and on), but you get the idea. Women are making waves in environmental health sciences through their robust, cutting-edge research.

Government is no exception. I am excited by the work of early career scientists, such as Tamara Tal, who is conducting innovative toxicological studies in zebrafish at the Environmental Protection Agency (EPA), and Kelly Ferguson, an environmental epidemiologist at the National Institute of Environmental Health Sciences (NIEHS) who studies how chemical exposures during pregnancy impact child health and development. And, I am inspired by the many women who are leaders within these agencies, such as Elaine Cohen-Hubal (Integrated Systems Toxicology Division, EPA), Kristina Thayer (Office of Health Assessment and Translation, NIEHS) Dale Sandler (Chronic Disease Epidemiology, NIEHS), and Nicole Kleinstreuer (National Toxicology Program Interagency Center for the Evaluation of Alternative Toxicological Methods, NIEHS).

We also have two phenomenal and highly accomplished women leading our environmental and public health agencies: Gina McCarthy (EPA) and Linda Birnbaum (NIEHS).

These are all women who I look up to tremendously and whose work I follow closely. But, on a more personal level, I have been fortunate to work directly with several amazing female scientists during my training so far. Pamela Lein (University of California, Davis) Stephanie Padilla (EPA), Elaine Faustman (University of Washington, Seattle), Sheela Sathyanarayana (University of Washington, Seattle), and Lianne Sheppard (University of Washington, Seattle) have all provided valuable mentorship and guidance to me.

So, while we do not yet have our first female president, this post is my way of acknowledging all of the incredible female scientists who have impacted my life through their work in environmental health sciences. Because of these inspiring, accomplished women (and the numerous others who I have not mentioned for the sake of brevity), I do not feel limited when I imagine my future. I have confidence that, with hard work and dedication, I can achieve what I set my mind to.

Thank you for being role models to me and the many other aspiring environmental health scientists of my generation!

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Me, in elementary school, already aspiring to follow in Rachel Carson’s footsteps

Reflections on Reform

There has been no shortage of news articles and blog posts about the recent passage of the Frank R. Lautenberg Chemical Safety for the 21st Century Act, which amends the ineffective and outdated 1976 Toxic Substances Control Act (TSCA). And, you probably don’t need to read another description of the strengths and weaknesses of the ultimate compromise. (If you do want a quick primer on why this reform matters, though, I would recommend this NPR interview with my former boss, Richard Denison, or his post on why this is a “really big deal.“)

Nevertheless, I want to add some reflections of my own on this historic occasion.

As a student in the environmental health field, this bill is particularly significant to me. Not only does the reform directly influence issues that I think about constantly, both personally and academically, but it will also likely set the stage for my future career.

It is exciting to think that I, along with fellow classmates in toxicology, environmental epidemiology, and exposure science programs across the country, will soon be able to participate directly in the implementation of this updated chemical safety system. We can feel a new sense of possibility with our work, instead of the backdrop of futility that comes when we learn in our foundational courses that – despite the damning evidence- the Environmental Protection Agency (EPA) could not even ban asbestos(!). With that (previous) reality in mind, could there be any hope that our efforts studying other potentially harmful chemicals would ever make an impact? As an analogy, what if there were a law that prevented the Centers for Disease Control and Prevention (CDC) from implementing effective vaccination programs? How would budding infectious disease epidemiologists feel about their opportunities for contributing to real public health advancements? Now, with the Lautenberg Act, we have a new framework in place that will at least offer the chance for us to use our research to make a difference. I hope that this will inspire others to join this dynamic, interdisciplinary field.

TSCA reform will impact and energize many aspects of environmental health. For example, the new mandate for safety reviews of all chemicals in active commerce will require investment in efficient and accurate screening tools. New testing technologies are already being developed, but further work and innovation – as well as input from a diverse array of scientists – will be necessary to ensure their reliability, relevance, and validity.

In addition, this reform will likely spur more research to understand the unique susceptibility of certain populations. The bill contains provisions that explicitly require protection of “potentially exposed or susceptible population[s].” This category includes “infants, children, pregnant women, workers, and the elderly,” but also other individuals who may be “susceptible to greater adverse health consequences from chemical exposures than the general population” – for example, because of their genetics. The study of gene-environment interactions (also known as “toxicogenetics”) aims to investigate specific genes that make some individuals more sensitive to chemicals. Dr. Francis Collins, director of the National Institutes of Health, summed up this idea with the phrase “genetics loads the gun, but the environment pulls the trigger.” Toxicogenetics is already a rapidly growing field, but I anticipate future work in this area will be crucial in helping us to determine the levels at which regulations should be set to ensure protection for those who are most vulnerable.

While there will likely be numerous positive consequences of the reform bill, the success of this updated chemical policy system is far from guaranteed. Numerous roadblocks may appear, such as the possibility of a mismanaged EPA or the paralyzing impact of endless cost-benefit analyses in risk management decisions. Passing TSCA reform was a difficult and momentous task, but the hard work will continue. We must maintain pressure to hold EPA accountable, prevent entanglement by special interests, and ensure the law is executed correctly. And, Congress must provide adequate funding to environmental health research programs, which will produce key scientific evidence to guide EPA and educate the next generation of scientists (like me!).

This compromise was not perfect, but the bill does represent a real improvement over the status quo. Now, the environmental health community has an exciting chance to help make its enactment as strong as it can be, through robust research and continued advocacy.

I can’t wait to play my part.

 

Mother’s Day Ethics

A few weeks ago, I had the privilege of hearing Dr. Steven Gilbert, founder of the Institute of Neurotoxicology and Neurological Disorders and Toxipedia, give a talk entitled “The Ethics of Epigenetics.” Epigenetics, an increasingly important concept in environmental health, introduces the possibility that environmental exposures can have trans-generational impacts. That is, certain compounds may be able to alter the way in which genes are expressed, so the effects of these exposures can manifest in the children and grandchildren of the exposed population.

As a graduate student in toxicology, the idea of epigenetics was not new to me. However, Dr. Gilbert incorporated a critical ethical dimension to his discussion that was inspiring and moving. He suggested the obvious yet often not explicit enough implication of epigenetics: that it demands an altered framework for policy and action, since what we are being exposed to (most of the time, without our consent) may impact not only ourselves but also future generations.

Mother’s Day may be an especially appropriate time to think about the consequences of epigenetics. As I celebrate my mother, I can’t help but think about how her mother’s exposures may have impacted her life and her health. I wonder the same about myself: how will my life course and health be affected by my mother’s and my grandmother’s exposures to chemicals? And, similarly, what about the effects of my own exposure to unregulated chemicals on my future children? (I should note, though, that epigenetic changes can also be passed down on the paternal side.)

How can we end this cycle? What will it take to ensure that Mother’s Day can be a celebration of family health instead of a reminder of family exposures and disease?

The only real solution is reform of the nation’s severely outdated and ineffective chemical safety law, the Toxic Substances Control Act (TSCA). We need a TSCA reform that is robust and can gain bipartisan support – now. Further delay is unethical, putting ourselves and our children at risk.