NAAQs

Is this Hazardous?

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By Kacee Deener 

How do you know when something isn’t good for you? Sometimes it goes without saying (rattlesnake venom), and sometimes it’s not as obvious and requires deeper evaluation.

I recently kicked off a blog series about human health risk assessment and described its four-step process.  Remember that hypothetical factory? How do we know if the chemicals being released are harmful? We use a process known as “hazard identification” to identify the types of health problems a chemical could cause (like cancer or respiratory effects).

IRISExamples of two EPA programs that develop hazard identifications are:  (1) the Integrated Risk Information System (IRIS) program and (2) the Integrated Science Assessment (ISA) program.  Through IRIS, Agency researchers provide health effects information on environmental chemicals. ISAs provide health effects information to inform the National Ambient Air Quality Standards for the six criteria air pollutants.

So, how do we do this? We start by searching the scientific literature to compile all of the studies that look at a chemical’s effects. In IRIS assessments, we describe how we search the literature using, in part, a diagram.  You can see an example of that here (pages 1-2).  We then organize the information into the categories of health effects seen in the studies, (e.g., kidney or reproductive effects) and summarize certain features of each study, such as the level and route of exposure. We also look at each study’s quality (e.g., was the study designed and conducted well? was it peer reviewed?).  Finally, we evaluate the overall “weight of evidence” to answer the question “does the agent cause the health effect?”

In some cases, EPA has developed “descriptors” for doing this. The Preamble to IRIS assessments provides more information (you can see an example here on page xxii). In other words, we provide text describing how likely it is that a health effect is associated with a chemical exposure. For example, in the recent IRIS assessment of 1,4-dioxane, we found that the chemical is likely to be carcinogenic to humans. In our recent ISA for Lead, we found, among other things, that there is a “causal relationship” between lead exposure and cognitive function decrements in children and a “likely causal relationship” between lead exposure and inflammatory responses in adults.

We’ve been working to improve the way we systematically review evidence when identifying hazards.  In fact, we recently held a workshop on this topic. We’ve also started releasing the literature search strategy, along with evidence tables summarizing the critical studies, early in the process of developing an assessment. We follow that up with a public meeting to discuss the materials. We held the first of these meetings on December 12-13. Our next meeting is scheduled for April 23.  Join us to provide your input, and don’t forget to check back in a few weeks for my next post!

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.

Please share this post. However, please don't change the title or the content. If you do make changes, don't attribute the edited title or content to EPA or the author.