National Center for Environmental Assessment

Human Health Risk Assessment—What it’s all about

Three images arranged horizontally: grade school students in classroom; girl with arms raised; bicyclists at sunrise

By Kacee Deener 

Scientists need to be able to describe—in a way everyone can understand—what we do and why it’s important.  That’s one reason I’ve decided that I need to strengthen my “elevator speech” about what I do (human health risk assessment).  I will be writing blog posts over the next several weeks trying to explain human health risk assessment in plain language.

For this first post, I’ll introduce the concept of risk and explain why human health risk assessment is important.

Risk is something we all understand.  In fact, we all assess risk every day.  What is the risk of swimming in the ocean on a clear day?  Does the risk change if there are jellyfish? How about an approaching storm?  A shark swimming nearby?  We all understand these types of risk calculations at a very intuitive level.

Human health risk assessment isn’t so different.  It’s a process of characterizing the nature of an environmental risk (in many cases, a chemical exposure) and determining how large that risk is to humans.  It consists of four steps: (1) hazard identification, (2) dose-response assessment, (3) exposure assessment, and (4) risk characterization.  I will discuss each in future posts.

So why is human health risk assessment important?  Well, chemicals are a part of life.  Some exist naturally; some are made by humans and can be released to the environment.  They bring benefits to our lives, but like most things, they also come with risks.

Let’s consider a hypothetical example.  Suppose a factory produces something you use every day.  To make this product, the company uses several different chemicals, and some chemicals are produced during the manufacturing process as byproducts.  Some are released to the air and water and may get into the soil.  Let’s say this industrial site is located next to a river that leads to your local drinking water plant.  Are any of the chemicals in that water?  Are the levels safe for you to drink?  What about your child? What levels of the chemicals are safe for you to breathe?

Human health risk assessment helps answer questions like these.  It is a tool that helps local, state and federal governments make decisions about what levels of chemicals can be in drinking water; what additional controls are needed to keep levels emitted to the air at a safe level; and what levels need to be achieved to clean up a contaminated site.  From a public health perspective, this is pretty important stuff.

In the coming weeks, I’ll be posting more about EPA’s human health risk assessment work. Stay tuned for those posts, but in the meantime, you can learn more by going to http://go.usa.gov/KhCJ.

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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EPA’s Continuing Effort to Reduce Lead Exposure

Three images in a line: child and adult hands together, lake shore, lead from periodic table.By Ellen Kirrane

As a kid growing up in the 1970s, I can remember my mom pulling up to the filling station and asking for “regular” gasoline.  At the time, I didn’t realize what this meant, but as I got older I found out that “regular” gasoline had lead in it; the other option – “unleaded” gas – did not.

Now, as a scientist working for EPA, I have a true appreciation for what lead is and how the next generation of kids can benefit from living in an environment that is cleaner because “regular” gasoline is no longer the norm.

By removing lead from gasoline and tightening industrial emissions standards, EPA has drastically reduced lead air emissions in the U.S.; they declined by more than two orders of magnitude (100 times) between 1970 and 2008.  But even with such important progress, by 2008 scientists realized that it was not enough, and that a young child’s cognitive function could be impacted by much lower lead exposures than previously understood. Supported with such science, EPA lowered its National Ambient Air Quality Standard for lead tenfold.

In June 2013, EPA released its most recent review of the science on the health and ecological effects of lead. Scientists who study lead consider it one of the “dirtiest” chemicals because it affects so many different systems in the body.  It does this by interfering with molecules called “ions.” When lead exposure affects ion status in the cells, it disrupts how calcium is regulated and how proteins are used for essential bodily functions.  This can lead to a wide array of health and ecological effects.

In children, lead exposure can cause IQ reductions and decreased academic performance. Lead can also cause behavioral changes in children, have harmful effects on blood cells and blood producing organs, and may cause decreased auditory and motor function, as well as immune effects.  Some of these effects may be irreversible and there is no evidence of a threshold below which scientists can be confident that there are no harmful cognitive effects from lead exposure. In adults, long-term lead exposure can cause increased blood pressure and hypertension, lead to coronary heart disease and affect many other organ systems. Just as lead can harm humans, it can also harm animals and other organisms that live on land and in the water by reducing survival, growth and reproduction, as well as affecting behavior, development and blood producing organs.

In addition to setting standards for lead in air, EPA continues to protect human health and the environment from the harmful effects of lead through a variety of programs.  EPA’s assessment of the science on the health and ecological effects of lead underpins these efforts. I am proud to be part of an agency that’s been working for four decades to keep lead out of our air, water, and soil.

To find out more about what EPA is doing to protect the American public from lead exposure, visit the Agency’s lead website at http://www2.epa.gov/lead.

About the Author:  Ellen Kirrane is an epidemiologist in EPA’s National Center for Environmental Assessment. She works on Integrated Science Assessments, which form the scientific basis for the National Ambient Air Quality Standards.

 

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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100 Days of EPA Science, and Beyond

By Kacee Deener

Numeral 100 with clouds and sky in backgroundEPA recently highlighted some of the Agency’s achievements during Gina McCarthy’s first 100 days as Administrator, noting that we have made significant strides towards improving the health of American families and protecting the environment across the country.

One of the seven highlighted examples is “Taking Action on Toxics and Chemical Safety” – which includes strengthening chemical assessments through changes to the Agency’s Integrated Risk Information System (IRIS) Program.  In a recent blog post, I described these changes and why they make sense for the IRIS Program, the Agency, and the American people.  But the IRIS Program hasn’t stopped there.  We’ve been moving forward implementing the changes.  Since August, we have:

  1. Released early materials for several chemical assessments.  These materials highlight our thought process for determining which studies are most important for the assessment, help make sure we didn’t miss any important research, and help identify potential scientific controversies early on.
  2. Scheduled the first IRIS public bimonthly meeting (Dec. 12-13).  At this meeting we will discuss the early materials for three chemicals (ETBE, tert-butanol, and RDX) and the draft assessments and peer review charges for two chemical assessments (ethylene oxide and benzo[a]pyrene).
  3. Held a public scientific workshop to discuss the IRIS assessment of hexavalent chromium.  An important component of determining the cancer causing potential of ingested hexavalent chromium is understanding the rates at which this metal is effectively detoxified in the gastrointestinal tract.  EPA convened an expert panel to discuss this issue in September; more than 200 stakeholders participated!
  4. Scheduled a scientific workshop on mouse lung tumors.  At this workshop, which will be held in early 2014, experts will discuss the available data from studies of mouse lung tumors following exposure to chemicals and discuss the relevance of these tumors in mice to assessing human cancer risk.
  5. Released final IRIS assessments for biphenyl, 1,4-dioxane (inhalation update), and methanol (noncancer). These final assessments provide information on the health effects of these chemicals and toxicity values that risk assessors can use (along with exposure and other information) to make decisions to protect public health.
  6. Announced a workshop on formaldehydeThis workshop, which will be held in spring 2014, will focus on several scientific issues pertinent to assessing the potential health effects of inhaled formaldehyde.  We’re taking input on speakers/panelists and topics for three theme areas – you can send us your suggestions here.

I think you’ll agree we’ve been making tremendous progress!  These activities illustrate our commitment to scientific integrity, public input, and transparency as we work together to produce the highest quality scientific assessments to inform decisions to protect public health.

About the Author: Kacee Deener is the Communications Director in EPA’s National Center for Environmental Assessment, home of the IRIS Program.  She joined EPA 12 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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EPA-Expo-Box: A Novel Innovation for Risk Assessors

By Dahnish Shams

Illustration of a toolbox

Click on the image to go to the EPA-Expo-Box website.

As a college student, I always found Wikipedia to be one of the simplest, yet most innovative resources created in the last decade. Wikipedia’s ability to compile and aggregate different information in a single spot on the internet makes it a unique web resource to accomplish any number of tasks across a wide variety of disciplines and settings.

Now—post graduation and working as a student contractor in EPA’s Office of Research and Development—I’ve found out that EPA scientists have developed their own innovative, encyclopedia-like resource for exposure assessment information. Links to databases, models, guidance documents and other resources are organized by topics such as exposure assessment approaches, chemical classes, environmental media, routes of exposure, life stages and populations, and more.

This new website, EPA-Expo-Box (short for EPA Exposure Toolbox), has compiled links to more than 800 exposure assessment tools all in one user-friendly format.

For example, imagine a scientist examining an outdoor air or water pollutant. This scientist could use EPA-Expo-Box’s Media Tool Set to help identify information needed to assess how this pollutant may be interacting with the environment, and tools needed to estimate exposures among the people who may come into contact with the air or water. This scientist could access resources on potential sources, fate and transport, or measured concentrations of the chemical in the air or water. With 800+ resources readily in hand, risk assessors can make informed scientific decisions to better protect the public and the environment from harm.

Prior to EPA-Expo-Box, there were no comprehensive publicly available resource for exposure assessment tools and information.  Recognizing this need, EPA scientists set out to design an online “one stop shop” for   resources that an exposure assessor may need. This free resource fills a specific niche in the risk assessment community. As an interactive scientific resource, it contains links to databases, models, guidance documents, and reference materials, along with step-by-step assistance for conducting exposure assessments to help guide users through the exposure assessment process.

Because it is completely online, users can access all of the tool sets at the touch of a button on their laptop, tablet, or smartphone. This versatility gives EPA scientists and others access to exposure assessment information regardless if they are in the field or in a laboratory. Like any good resource, EPA-Expo-Box is simply a handy tool to have when you need it most.

The other advantage of an online-only platform?  When new resources become available, updates can be made quickly and easily. No longer will users have to wait for the next edition or version to get the most up to date information. The dynamic nature of EPA-Expo-Box is increasingly crucial in the ever changing field of risk and exposure assessment.

Day in and day out, it is versatile and dynamic innovations like EPA-Expo-Box that better help EPA and others access information they need to more effectively evaluate potential risks to human health and the environment in the communities in which we all live and work.

About the Author: Dahnish Shams is a student services contractor working with EPA’s National Center for Environmental Assessment in communications.

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 Does Truly Matter

By: Dahnish Shams

As an EPA summer intern, I got a firsthand look at how essential science is to the operations of the Agency and of its immense importance to us all.

Stationed at EPA’s National Center for Environmental Assessment, I was quickly introduced to some of the science products that support so much of what EPA does to protect human health and the environment. Chemical assessments in EPA’s Integrated Risk Information System (IRIS) Program and Integrated Science Assessments (ISAs) for the six criteria air pollutants (ozone, particulate matter, carbon monoxide, sulfur oxides, nitrogen oxides, and lead) inform the public and decision makers of the potential hazards threatening public health and the environment. These scientific products provide the basis for many of the rules the agency generates.

Yet, when you look beyond the products and their implications, what I have learned during my 10-week internship is that so much of the Agency’s work is truly defined by individuals, such as the scientists, communications staff, and support specialists that work as a team to conduct assessments. I saw that despite numerous obstacles, there is continued determination by this team of professionals to consistently devise strategies and methods to overcome the challenges that naturally arise as chemicals and humans interact in increasingly complex ways with the environment.

So as I conclude my internship, this blog post is meant to acknowledge the passion, determination, and teamwork exemplified by the people that I have met at the Agency this summer. These qualities are reflected through the continued efforts to improve IRIS chemical assessments, through climate assessments of ecosystems from across the country, and by the continual production of high quality ISAs – all of which provide a critical part of the scientific foundation for EPA’s decisions to protect human health and the environment.

If there is one message that I will take away from the Agency this summer, and one that I hope you gather from this post, is that I am proud to have been associated with EPA, and with the National Center for Environmental Assessment and the people that work here in particular. Though there are challenges in assessing the environment in the 21st century, they showed me through their passion, dedication, and teamwork that producing high quality science does truly matter.

About the Author: Dahnish Shams was a summer intern with EPA’s National Center for Environmental Assessment.

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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