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Technology for Community Resiliency

2014 August 1

By Paul Lemieux

This week I was honored to participate in the White House Innovation for Disaster Response and Recovery Demo Day. From finding an open gas station to finding a safe place to sleep at night following a disaster or finding a vehicle you can rent by the hour, participants shared a variety of amazing technology applications to help make communities more resilient in the aftermath of disaster.

Me giving a presentation on I-WASTE at the White House's Old Executive Office Building.

Paul giving a presentation on I-WASTE at the White House’s Old Executive Office Building.

While there were some great private sector tools from big innovators like Airbnb, Google, Microsoft, SeeClickFix, and TaskRabbit there were just as many amazing tools from government innovators, too.

An example of some of the government tools highlighted during the demo:

The National Geospatial-Intelligence Agency (NGA) announced GeoQ, a tool that crowdsources geo-tagged photos of disaster-affected areas to assess damage over large regions. Developed in coordination with NGA, the Presidential Innovation Fellow Program, the Federal Emergency Management Agency (FEMA), and other disaster analysts, GeoQ improves the speed and quality of disaster-related data coordination by using a data crowd-sharing framework. Programmers can use the existing services and add features to customize the GeoQ code for their own community.

The U.S. Geological Service (USGS) highlighted ShakeMap and other post-earthquake information tools that offer rapid situational awareness for disaster response and recovery. Using data from seismic monitoring systems maintained by USGS and its state and university partners, ShakeMap provides a rapid graphical estimate of ground shaking in an affected region on the web within minutes of an event. The maps and underlying data, which can be downloaded in numerous formats for use in GIS and other applications, are also the basis for ShakeCast—which enables emergency managers at a growing number of companies, response organizations, and local governments to automatically receive USGS shaking data and generate their own customized impact alerts for their facilities.

And I showcased EPA’s I-WASTE, a flexible, web-based, planning and decision-making tool to address disaster waste management issues. I-WASTE offers emergency responders, industry representatives, and responsible officials reliable information on waste characterization, treatment, and disposal options, as well as guidance on how to incorporate waste management into planning and response for natural disasters, terrorist attacks and animal disease outbreaks.

It is clear that there are a number of public and private organizations working together with individuals and communities around the country to ensure that together we are prepared and ready to respond to the next disaster we might face.

Watch a video of how I-WASTE can help your community, embedded below, or go to


Paul Lemieux, Ph.D. works on issues related to clean up after chemical/biological/radiological attacks and foreign animal disease outbreaks. Paul has also been working to develop computer-based decision support tools to aid decision makers in responding to wide-area contamination incidents. He is the Associate Division Director of the Decontamination and Consequence Management Division of U.S. EPA’s National Homeland Security Research Center.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action.

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Modeling Fish on the Move

2014 July 31

By: Marguerite Huber

How many places have you lived? Why did you move? Personally, I have lived in eight different places because of school and jobs. Other people move to find better opportunities, like housing or a place to raise their children.

Fish are sometimes forced to move as well. But, unlike you and I, fish cannot just get up and move across towns, states, and countries. They have to move across their own river networks to maximize survival.

For fish, the availability of sufficient spawning and rearing habitats can strongly influence the productivity of an entire river network. Fish also move based on certain environmental drivers like warming temperatures, and human activities such as land development, building of dams, and changes in stream channels, which can contribute to water pollution or alter fish habitat. Additionally, fish are affected by their interactions with other species. When different species interact, they can compete for resources or have a predator-prey relationship.

The Willamette river network, color-coded to show which of the 3 primary environmental conditions are currently most limiting habitat suitability for Chinook salmon, a species of high management concern.

The Willamette river network, color-coded to show which of the 3 primary environmental conditions are currently most limiting habitat suitability for Chinook salmon, a species of high management concern.

To fully understand fish in their changing environment, EPA researchers created a model that simulates groups of fish in river landscapes. This model helps determine how fish populations reproduce, move, and survive in response to both environmental drivers and species interactions. It is designed to help EPA assess the impacts of land development on fish assemblages, and better understand how these impacts may be intensified by climate change.

The researchers studied how Chinook salmon (Oncorhynchus tshawytscha) respond to steepness of the stream channel, flow, and temperature in the Willamette River basin of Oregon. This region is important to study because it is expected to experience substantial rises in human population and water demand over the next 50 years. The model, which can be applied to any watershed, helped create a map of the salmon’s abundance and distribution in the Willamette River basin. To capture species interaction, scientists also modeled the abundance of another fish, the northern pikeminnow (Ptychocheilus oregonensis), a native predator and competitor of Chinook salmon.

Afterwards, researchers modeled both species together, accounting for projected effects of competition and predation. They found that species interactions and temperature affect both Chinook salmon and northern pikeminnow. The results show species distributions throughout the basin and their projected responses to future stressors such as climate change, water consumption, and hydropower management.

Not only will EPA’s model help construct a map of fish on the move, but it will help inform the science used to develop water quality regulations and trading, help prioritize restoration, and advise management decisions.

About the Author: Marguerite Huber is a Student Contractor with EPA’s Science Communications Team

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action.

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Science for Sustainable and Healthy Tribes

2014 July 25

Crossposted from EPA’s Leadership blog.

EPA Administrator Gina McCarthy

By EPA Administrator Gina McCarthy

Yesterday I signed the Policy on Environmental Justice for Working with Federally Recognized Tribes and Indigenous Peoples, which clarifies how EPA works with federally and state recognized tribes, indigenous community-based grassroots organizations, and other indigenous peoples to address their environmental and public health concerns.

American Indian communities have been inextricably tied to the natural environment for generations. From cultural identify to sustenance, many of those unique traditions endure. That’s why I’m so excited about the six tribal environmental health research grants to tribal communities and universities that we recently announced.

EPA is proud to have a long and rich history of supporting environmental and public health protection for all communities. These EPA supported grants will increase our knowledge of the threats posed by climate change and indoor air pollution, while incorporating traditional ecological knowledge to reach culturally appropriate and acceptable adaptation strategies to address these threats.

There is a unique need for tribal-focused research to identify those climate-related impacts and to reduce associated health and ecological risks. EPA has been actively engaged in supporting such research, and I’m thrilled EPA is providing grants to further that work. The grants will support the study of the impacts of climate change and indoor air pollution on tribal health and way of life. Grantees include:

  • The Alaska Native Tribal Health Consortium located in Anchorage, Alaska will be looking at ways to assess, monitor, and adapt to the threats of a changing climate to the sustainability of food and water in remote Alaska native villages.
  • The Swinomish Indian Tribal Community in La Conner, Washington will be examining coastal climate impacts to traditional foods, cultural sites, and tribal community health and well-being.
  • Yurok Tribe in Klamath, California will be identifying, assessing, and adapting to climate change impacts to Yurok water and aquatic resources, food security and tribal health.
  • Little Big Horn College in Crow Agency, Montana will research climate change adaptation and waterborne disease prevention on the Crow Reservation.
  • The University of Tulsa in Tulsa, Oklahoma, will examine ways to improve indoor air quality and reduce environmental asthma triggers in tribal homes and schools.
  • The University of Massachusetts-Amherst in Amherst, Massachusetts will measure indoor air quality in tents as related to wood smoke exposures and identify potential health risks in remote subsistence hunting communities in North America.

The health of our communities depends upon the health of our environment. These grants will help build prosperous and resilient tribal communities both now and for future generations. Like the enduring memories of my tour of the Standing Rock Sioux Reservation and tribal environmental program in North Dakota, they will have an impact long after my service as EPA Administrator.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action.

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Changing Times: EPA’s Report on National Trends

2014 July 24

By Gaelle Gourmelon

Some things in my childhood memories look different when I revisit them as an adult. That tall slide in the playground? It’s really only four feet high. The endless summer bike rides to the beach? They now take ten minutes. Sometimes, however, things seem different because they’ve actually changed. I recently went to a favorite childhood beach and saw that the dock was now stranded in the water, no longer reachable from the beach. Undeniable evidence of the changing coast.

But what evidence do we have to observe real changes over time when it comes to our national environment? What data can we use to determine if our environment has meaningfully changed?

To help answer these questions, EPA released the draft Report on the Environment 2014 (ROE 2014) for public comment in March, and it will undergo external peer review on July 30-31, 2014.

The ROE 2014 is not an intimidating, technical tome; it is an interactive website, full of national-level environmental and health indicators and is designed to make it easier to find information on national environmental trends. It’s not a giant, unwieldy database. Rather, it’s a summary of important indicators that paints a picture of how our environment is changing.

Why use indicators?

Just like having a high temperature indicates you are sick, environmental indicators help us understand the health of the environment. ROE indicators are simple measures that track the state of the environment and human health over time.

For example, if we want to understand the nation’s air quality, we can measure indicators such as lead emissions, acid deposition, and particulate matter concentrations to give us clues about overall changes. These indicators can help us make informed decisions about conditions that may otherwise be difficult to measure.

Report on the Environment

An exhibit for the acid deposition indicator gives us a clue about the changes in the quality of outdoor air in the US.


What’s included in the Report on the Environment?

Data for the ROE indicators come from many sources, including federal and state agencies as well as non-governmental organizations. EPA brought together scientists and other experts to determine what data are accurate, representative, and reliable enough to be included. With feedback from the public and our partners, we selected 86 indicators that help to answer questions about air, water, land, human health and exposure, and ecological condition. The ROE 2014 also includes new indicators on aspects of sustainability.

Why do we need the Report on the Environment?

EPA designed the ROE to help answer mission-relevant questions and help us track how we’re doing in meeting environmental goals. But because the ROE 2014 is an easy-to-use, interactive website, scientists, decision-makers, educators, and anyone who is curious about the environment and health can view the most up-to-date national (and sometimes regional) data, too. The ROE shows trends and sets up baselines where trend data do not yet exist. It also highlights gaps where we don’t have reliable indicators.

How can I participate in the external peer review meeting?

EPA is committed to proactively engaging stakeholders, increasing transparency, and using the best available science. By releasing the draft ROE 2014 for public comment and peer review, we benefit from stakeholder and scientific engagement to support the best conclusions possible. The draft ROE 2014 website will be reviewed by EPA’s Science Advisory Board in a public meeting on July 30-31, 2014. For additional meeting details, visit the July 11, 2014 Federal Register Notice and the SAB meeting website.

How can I stay connected with the ROE?

Everyone can use the ROE to inform their discussions of environmental conditions and related policies in the U.S. The information it provides helps you understand your environment, and encourages you to ask more questions about your environment and health. Now, it’s time to investigate. Things might have changed more than you think.

Sign up to be notified about the upcoming release of the final Report on the Environment 2014; you can also receive periodic updates and highlights.

About the author: Gaelle Gourmelon was an Association of Schools and Programs of Public Health Fellow working on EPA’s Report on the Environment project from September 2012 through May 2014. Her background in biology and environmental health has fueled her passion for reconnecting people with their natural and built environment.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action.

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Monitoring Harmful Algal Blooms? There’s an App for That!

2014 July 17

By Annie Zwerneman

Algal bloom covers a lake.

Algal bloom covers a lake.

I was recently on my favorite hiking trail, which passes by a beautiful lake. But this time hiking past it, I noticed a strange, dark scum creeping along the shoreline of the water. I learned later that this scum was actually an algal bloom: a population of algae increasing quickly over a short period of time.

Some algal blooms are merely an eyesore, but others fall into a more serious category called “harmful algal blooms” (HABs): algae and cyanobacteria (formerly known as blue-green algae) that remove oxygen from the water, crowding their way along the surface and producing toxins that are harmful to animals. The toxins that HABs produce can affect peoples’ health, too.

EPA has been working to monitor HABs, including taking water samples to see where and how algal blooms may affect you. Unfortunately, taking such water samples is time-intensive, so EPA has been working alongside scientists at the National Oceanic and Atmospheric Administration (NOAA), National Aeronautics and Space Administration (NASA), and the United States Geological Survey (USGS) to find new ways to monitor the quality of inland water bodies, such as lakes and reservoirs. EPA hopes to monitor estuaries and coastal waters in the future as well.

A new Android app is being developed that displays imagery of cyanobacterial cell counts in freshwater systems, which can indicate the presence of HABs. Expected to be in beta testing this fall, the app will provide information necessary for locating and monitoring HABs. It’s primarily aimed toward stakeholders like health departments and municipalities (such as water treatment plants).

The app will display data from NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) satellite. In the near future, EPA researchers hope to incorporate the European Space Agency’s Sentinel-3 and potentially the Landsat-8 satellite as well. They will work with their NOAA, USGS, and NASA partners to pull all these capabilities together once the app is ready for public use.

The way the app will work is a bit like the weather station. At the beginning of each week, the cell count will be updated based on the satellite information gathered the previous week. There may even be a prediction of the cell count for the upcoming week available. For example, you can get a cell count in Lake Erie for the current week, and then get a prediction of what the cell count may be next week.

Thanks to the collaborative effort of multiple federal agencies, those looking for information about freshwater quality and HABs won’t have to look far: there will be an app for that!

About the Author: Annie Zwerneman is a 2014 summer intern working for the EPA’s Office of Research and Development.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action.

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Good Science Starts with Good Ethics

2014 July 16

By Toby Schonfeld, Ph.D.

Young woman looks at EPA's Facebook pageThe social media world was rocked recently when a paper published in a scientific journal revealed that Facebook had been manipulating users’ news feeds to determine whether the concept of “emotional contagion” was the same in virtual contexts as it was in person. You know how the whole office lights up when one person gets flowers? Researchers wanted to confirm the hypothesis that the same kind of emotional transfer can happen in a virtual context devoid of non-verbal cues. Turns out: it can.

The problem with this study isn’t the science—it’s the ethics of the research. Specifically, the complaint is that investigators never obtained informed consent from Facebook users to participate in this research study.

Why should that matter? Here’s the problem: without giving members the option to choose whether or not they wanted to participate in research, the investigators treated people simply as a means to an end—in this case, to verifying their hypothesis. And there’s no guarantee that the researchers’ ends were the same as mine.

We treat many things as a means to an end—we use planes, trains, and automobiles to get us from place to place, and we use food and water to nourish our bodies. But people are not like autos or apples: people have interests, desires, and preferences. I am the only one who truly knows what my values, goals, and priorities are, and therefore I’m the only one who can decide whether or not participation in research coincides with those goals.

Facebook points out that users agreed—via the fine print—to participate in this kind of work when they agreed to the terms of service. But that argument doesn’t work either. Nobody can agree to unspecified future research; after all, how would one be truly “informed” about research that the investigators haven’t even imagined yet? The best that can be expected is that individuals can agree to be contacted for future research—and that’s what should have happened here.

Some would argue that there are no real “risks” here—they were not injecting anyone with a drug, or asking them to exercise to the point of exhaustion, or even asking them potentially sensitive survey questions. And because there are no risks, they claim, they didn’t need to ask permission.

But think about how it makes you feel to know that your news feed—and therefore your emotions—may have been manipulated without your knowledge or consent. Do you feel hurt? Confused? Violated? That’s a natural consequence when investigators fail to abide by an important ethical foundation of human subjects research known as respect for persons. The investigators failed to recognize that their subjects were autonomous individuals capable of self-determination and therefore had a right to opt out of this study.

At EPA, we take the informed consent process seriously. Whether you’re approached to be part of a study in our Healthy Heart program, or to help investigators understand more about how the environment affects your child’s asthma, EPA scientists will first explain the research to you so that you can judge whether or not participation makes sense for you and your family.

Good ethics starts with good science. But as we learn from this example, good science needs good ethics, too.

About the Author: Dr.Toby Schonfeld is EPA’s Human Subjects Research Review Official and the Director of the Agency’s Program in Human Research Ethics and Oversight.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action.

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Saving Energy and Money: Go Team Go!

2014 July 14

By Lek Kadeli

Portrait of Lek KadeliSpirited competition between local schools is a time honored tradition. From the football and soccer teams to the debate club, nothing beats taking on your arch rival to spark school spirit, get the neighbors talking, and build community pride.

That spirit of competition has helped schools here in the District of Columbia save more than 76,000 kilowatt-hours of electricity, thanks to Lucid—an EPA-supported small business started by previous winners of the agency’s People, Prosperity and the Planet (P3) award.

The schools vied to see which could most dramatically reduce their energy consumption as part of the three-week “Sprint to Savings” competition. The DC Green Schools Challenge set up the competition to help schools conserve energy and save money while “engaging students in real-world learning opportunities.” It is managed by the the District of Columbia, Department of General Service (

To monitor their progress and take action, students used Lucid’s “Building Dashboard,” a software program that monitors a building’s energy and water consumption in real time and presents that information in easy-to-understand graphic displays on computer screens or other devices.

Students were able to use Building Dashboard installed at their schools to gauge their progress in 15-minute intervals and help the school take corrective action, such as switching lights off when not needed, shutting down unused computers and monitors, and turning the heat down after hours. A District-wide leader board helped them keep an eye on the competition.

Interactive Building Dashboard

Interactive Building Dashboard

The idea for a data monitoring display system begin when the now principal partners of Lucid Technology were students at Oberlin College. In 2005, their prototype won an EPA P3 Award. The P3 program is an annual student design competition that supports undergraduate and graduate student teams to research and design innovative, sustainable methods and products that solve complex environmental problems. Since then, there’s been no looking back!

Today, we are thrilled to announce that Lucid is among 20 other small businesses—including two other former P3 winners—selected to receive funding as part of the EPA’s Small Business Innovative Research (SBIR) program. The program was designed to support small businesses in the commercialization as well as the research and development of technologies that encourage sustainability, protect human health and the environment, and foster a healthy future. Environmental Fuel Research, LLC, and SimpleWater, LLC are the other two former P3 winning teams.

Thanks to Lucid, Environmental Fuel Research, LLC, SimpleWater, LLC and the other innovative small businesses we are supporting today, winning ideas are bringing products to the marketplace that protect our environment while sparking economic growth. I’ll bet that even arch rivals can agree that’s a win for everyone.

About the Author: Lek Kadeli is the Acting Assistant Administrator in the Agency’s Office of Research and Development.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action.

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Ushering In a New Generation of Chemical Screening

2014 July 14

By Richard Judson

I work with EPA colleagues and other scientists around the world to integrate advances in biology, biotechnology, chemistry, and computer science to evaluate thousands of chemicals. Part of our research is supporting EPA’s Endocrine Disruptor Screening Program, exploring the potential for chemicals to disrupt normal growth and development in humans and other animals.

The work we do is helping usher in a new generation of faster, more efficient, and far less costly chemical screening methods. We use automated technologies, called high-throughput screening assays, to expose cells and proteins to chemicals. We then screen them to identify any that exhibited changes in biological activity that may suggest the potential for endocrine disruption.

My partners and I are excited to announce that we have recently published two papers on results of our work. We used the innovative methods described above to screen chemicals for their potential to mimic normal estrogen hormones, substances that direct development and reproduction. Exposure to chemicals that mimic estrogen pose a range of potential health risks, including birth defects and certain types of cancer.

The first paper, published in Nature Scientific Reports, describes the results of screening approximately 10,500 chemicals. The screening included 88 duplicates of the same chemicals, which validated the reliability of the assays. It also included 39 reference chemicals—those whose estrogen-receptor activity have been well established through traditional testing methods. Using the reference chemicals showed that the assays could accurately identify chemicals that were both positive and negative for their ability to mimic natural estrogens.

Robotic arm moving samples for screening

Robotic arm moves samples for automated chemical screening, part of the Tox 21 collaboration.

This paper is a product of Tox21, a federal collaboration pooling expertise and resources among EPA, the National Toxicology Program (National Institute of Environmental Health Sciences), the Food and Drug Administration, and the National Center for Advancing Translational Sciences (NCATS). Tox21 was established to study how high-throughput screening methods can be used to evaluate thousands of chemicals. These assays were run on the NCATS ultra-high-throughput robotic screening system (pictured).

The second paper (selected by the American Chemical Society’s Environmental Science and Technology journal as an editor’s choice) describes the results of screening 1,814 chemicals (including 36 reference chemicals). The screening was performed using a panel of 13 high-throughput estrogen receptor assays that use a diverse set of cell types and assay technologies.The results indicate that such a panel can accurately predict estrogenic responses. It demonstrates how the resulting data could be used for chemical prioritization as part of the Agency’s Endocrine Disruptor Screening Program.

In December 2013, we publicly released our high-throughput screening data through user-friendly web applications called interactive Chemical Safety for Sustainability (iCSS) Dashboards. I encourage anyone with an interest in this research to take a look at the data and to also participate in EPA’s Second ToxCast Data Summit. The summit is scheduled for September 29-30, 2014 in Research Triangle Park, NC.

The goal of the summit is to bring together the user community (industry, non-governmental organizations, academia, governmental agencies and more) to present their ideas for ways to use the large amount of high-throughput screening data to help inform chemical policy and regulatory decisions.

About the Author: EPA scientist Dr. Richard Judson develops databases and computer applications to model and predict toxicological effects of a wide range of chemicals. He is a member of the EPA Computational Toxicology research team where he leads the effort in bioinformatics. Dr. Judson has a BA in Chemistry and Chemical Physics from Rice University and an MA and PhD in Chemistry from Princeton University.

Information About the Papers

Profiling of the Tox21 10K compound library for agonists and antagonists of the estrogen receptor alpha signaling pathway.  Ruili Huang, Srilatha Sakamuru, Matt T. Martin, David M. Reif, Richard S. Judson, Keith A. Houck, Warren Casey, Jui-Hua Hsieh, Keith Shockley, Patricia Ceger, Jennifer Fostel, Kristine L. Witt, Weida Tong, Daniel M. Rotroff,2 Tongan Zhao, Paul Shinn, Anton Simeonov, David J. Dix, Christopher P. Austin, Robert J Kavlock, Raymond R. Tice, Menghang Xia. Nature Scientific Reports

Predictive Endocrine Testing in the 21st Century Using in Vitro Assays of Estrogen Receptor Signaling Responses. Daniel M. Rotroff, Matt T. Martin, David J. Dix, Dayne L. Filer, Keith A. Houck, Thomas B. Knudsen, Nisha S. Sipes, David M. Reif, Menghang Xia, Ruili Huang, and Richard S. Judson. Environmental Science & Technology

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action.

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I’ll Trade You: Water Quality Science Edition

2014 July 10

By Marguerite Huber

Landsat image of Chesapeake Bay

Chesapeake Bay watershed includes six states and the District of Columbia. Image: NASA/Goddard Space Flight Center Scientific Visualization Studio

The outcome of a trade can sometimes be the luck of the draw. You may not have gotten a better sandwich for the one you traded at lunch, or the all-star pitcher your team acquired in that mid-season trade may turn out to be a bust.

On the other hand, the best kind of trade is one where everybody wins. EPA researchers are helping bring just that kind of trade to improve water quality.

Chesapeake Bay is an expansive watershed that encompasses some or all of six states and the District of Columbia. High levels of nutrients flowing in from all over that expansive watershed decrease oxygen in the water and kill aquatic life, creating chronic and well-known dead zones.

To help, EPA established the Chesapeake Bay Total Maximum Daily Load (TMDL), which sets a cap on nutrient and sediment emissions to restore water quality, ensure high quality habitats for aquatic organisms, and protect and sustain fisheries, recreation and other important Bay activities.

Recent innovations in Chesapeake Bay and elsewhere have promoted a new type of trading, called water quality trading, to meet watershed-level reductions in nutrient pollution. The goal is to facilitate individual flexibility and responsiveness while creating incentives to reduce overall nutrient flow from both agricultural and urban areas.

Here is how water quality trading would work…

Farmers and wastewater treatment plants have the opportunity to team up to collectively meet the water quality goal by reducing nutrients. While both entities have their own baseline nutrient emission level they must shoot for, they can gain tradable credits if they do better. A farmer that plants nitrogen-absorbing crops such as barley and wheat can sell the credits they gain to a wastewater treatment plant that needs to reduce its own emissions.

Silhouette of kids on dock at sunset

A healthy Chesapeake is a win for everybody!

Trading is based on the widely different costs it can take to control the same kind of pollutant, depending on its source and location. For example, upgrading wastewater treatment plants and ripping up urban streets to replace leaky stormwater drainage pipes could cost billions of dollars. On the other hand, planting new or different crops is much less expensive.

Like the TMDL itself, the development of the water trading system began with science. EPA-supported scientists and economists developed a computer model to find the least costly mix of pollution-reduction options across the watershed for meeting the TMDL. The model also has been used to explore how different trading policies could help to meet TMDL requirements, and as the basis for analyzing policies leading to the nutrient trading guidelines for Chesapeake Bay.

Overall, water quality trading depends on cooperation across the watershed to help achieve faster, less expensive pollutant reductions that improve the Bay’s water quality. It’s a win-win for everybody.

About the Author: Marguerite Huber is a Student Contractor with EPA’s Science Communications Team.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action.

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The Dose Makes the Poison – or does it?

2014 July 8

By Kacee Deener Three images arranged horizontally: grade school students in classroom; girl with arms raised; bicyclists at sunriseWhen I was a graduate student, one of the first lectures in my toxicology class was about the history and basic principles of toxicology. We learned about Paracelsus, the 16th century physician-alchemist known as the father of toxicology, and how he coined the phrase “the dose makes the poison.” This has been a central tenant of toxicology and an important concept in human health risk assessment. The more we learn about the health effects of chemicals, however, the more we realize things may not be quite this simple.

I recently wrote about identifying the hazards of chemicals. Once we know what such hazards are, how do we know what levels of exposure will cause those health effects in humans? This is a really important question. To answer it, scientists do something called dose-response analysis, the next step in the human health risk assessment process. To do this, scientists calculate how different amounts (exposures or doses) of a chemical can impact health effects (responses) in humans.

Scientists measure these amounts both externally (outside the body) and internally (inside the body). External measurements, exposure levels, are the amount of a chemical in an external media, such as air, water, or soil. Internal dose refers to the amount of a chemical that actually gets into a person’s body after ingesting or inhaling something (like food or air) that contains the chemical.

Often, as the internal dose or exposure level increases, the response or health effect also increases—though there are exceptions to this. Additionally, sometimes we don’t have data about effects at doses lower than what might be tested in studies, so we have to mathematically extrapolate to estimate the effects below the observed data. Traditionally we have done this using different approaches for cancer versus other health effects, but this may change as our scientific understanding of disease processes improves.

Why is dose-response assessment important? First, it helps us understand what happens in the human body at different levels of exposure to a chemical, and it allows us to see that relationship presented graphically. Second, it allows us to derive toxicity values (described in the table below) that become important when we develop a complete risk assessment.

Toxicity Value Name Description
Reference Dose (oral exposures) The amount of a substance that one can ingest every day for a lifetime that is not anticipated to cause harmful health effects.
Reference Concentration (inhalation exposures) The amount of a substance that one can breathe every day for a lifetime that is not anticipated to cause harmful health effects.
Oral Slope Factor An estimate of the increased cancer risk from a lifetime of oral exposure to a substance.
Inhalation Unit Risk An estimate of the increased cancer risk from a lifetime of inhalation exposure to a substance.

We want to make sure we are protective of sensitive groups of people when we calculate toxicity values. To do that we may apply scientifically-based factors to account for uncertainty in various areas, such as differences between animals and humans (if we start with animal data), differences among humans (such as genetics, life stages, etc.), and scientific data gaps (for example, certain health endpoints that have not been evaluated). In EPA’s Integrated Risk Information System (IRIS) Program, we’ve started developing multiple toxicity values for different organ systems or health effects seen in the data.

The toxicity values resulting from dose-response assessment are used as part of a larger calculation to estimate risk from exposure to environmental contaminants. I’ll talk more about that in a few weeks. Until then, check out an example of dose-response assessment in Section 2 of the IRIS assessment of benzo[a]pyrene. And read more about dose-response assessment on the Agency’s risk assessment website.

About the Author: Kacee Deener is the Communications Director in EPA’s National Center for Environmental Assessment.  She joined EPA 13 years ago and has a Masters degree in Public Health.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action.

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