Integrated Risk Information System (IRIS)

EPA’s Integrated Risk Information System Assessment of Ammonia

By Salina Tewolde and Lou D’Amico, Ph.D.

The first thing that probably comes to your mind when I say “ammonia” is that household product you use to clean just about anything in your house. Besides being used as an all-purpose cleaner, ammonia also occurs naturally in air, soil, and water. As you’re reading this, you’re producing ammonia too – it’s used in nucleic acid and protein synthesis, and helps your body maintain its acid-base balance – all part of normal biological processes.

The largest and most significant use of ammonia is in agricultural fertilizers, which represents about 80% of commercially produced ammonia. Ammonia is also used in food products as an antimicrobial agent, in water purification, and in refrigeration systems. It’s also an important chemical intermediate in the production of pharmaceuticals and other chemicals, and is used to reduce nitrogen oxide emissions from combustion sources like some industrial boilers and diesel engines. Some major sources of ammonia gas come from leaks and spills during the production, storage, or processing stages of the chemical. Other sources include decaying manure from livestock, application of fertilizers in agricultural, and sewage or wastewater emissions in the environment. EPA’s Toxic Release Inventory reports that over 150 million pounds of ammonia was released from reporting facilities in 2014.

There are a number of ways that humans can be exposed to ammonia. The most common route of exposure is through breathing air that contains ammonia. Humans can be exposed to ammonia gas from household cleaning products or through direct skin contact via products that contain the chemical. Livestock and poultry farmers that work in animal feeding operations or confinement areas can be exposed to ammonia released from animal waste, and farmers can be exposed when applying ammonia-containing fertilizers to fields.

IRIS spelled out with flowers in the backgroundTo characterize the potential health effects that humans can acquire from inhaling high concentrations of ammonia, EPA recently released an Integrated Risk Information System (IRIS) assessment that looks at the noncancer health hazards that may result from inhalation of ammonia.

EPA’s assessment evaluates chronic inhalation exposure to ammonia, observed at levels that exceed naturally-occurring ammonia concentrations. Human and animal studies showed that inhalation exposure had an effect on the respiratory tract in humans, which is the site of direct contact when ammonia is inhaled. This hazard determination was based on findings from multiple epidemiology studies in human populations exposed to ammonia in different settings (workers in industrial, cleaning and agricultural settings, volunteers exposed for up to 6 hours under controlled conditions, as well as case reports) and animals (short-term and subchronic studies in several species and across different exposure patterns). Short-term inhalation exposure to high levels of ammonia in humans can cause irritation and serious burns in the mouth, lungs, and eyes. Chronic exposure to airborne ammonia may increase the risk of respiratory irritation, cough, wheezing, tightness in the chest, and decreased lung function.

EPA’s IRIS assessment includes an estimate of the amount of ammonia that one can breathe every day for a lifetime that is likely to be without harmful health effects. This is known as an inhalation reference concentration, or RfC. The RfC was derived from an occupational study by Holness et al. (1989) that looked at the relationship between decreased lung function and long-term exposure to ammonia from workers at a soda ash plant. Ammonia was last evaluated by the IRIS Program in 1991, and as a result of the reevaluation posted this week, the RfC is five-fold higher (less stringent) than what was previously on the IRIS database. You can learn as much as you care to about ammonia inhalation toxicity through either reading the Toxicological Review on the IRIS Ammonia webpage, or getting the highlights through the accompanying IRIS Summary.

IRIS assessments go through rigorous review prior to finalization. This ammonia assessment was reviewed by EPA’s program offices and regions and other federal agencies, as well as external peer review by the Science Advisory Board Chemical Assessment Advisory Committee. The public also had opportunity to comment. All of this information is available on the IRIS chemical-specific page for ammonia, and demonstrates the IRIS Program’s commitment to transparency while providing high quality, publicly available information on the toxicity of chemicals to which the public might be exposed.

Reference:  Holness, DL; Purdham, JT; Nethercott, JR. (1989). Acute and chronic respiratory effects of occupational exposure to ammonia. AIHA J 50: 646-650.

About the Authors: Salina Tewolde is a student contractor and writer working with the science communication team in EPA’s Office of Research and Development. Lou D’Amico is the Acting Communications Director for the National Center for Environmental Assessment, which houses the IRIS Program.

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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A Job Worth Doing is Worth Doing Together

By Janice Lee 

Arsenic element from periodic tableMost everyone recognizes the value of teamwork. We learned this from a young age in school, and most people can point to a professional experience where a project has improved because of group input. For me, a terrific example is the inorganic arsenic health assessment that EPA is currently developing through our Integrated Risk Information System (IRIS)—a program that provides information on the health effects that may result from exposure to environmental contaminants.

Arsenic is well known—it’s been used since ancient times for a variety of purposes, it had a major role in the Hollywood movie Arsenic and Old Lace, and many people are familiar with health issues that occur in areas where naturally-occurring arsenic shows up in high levels in drinking water.

Throughout 2013, our team met with a lot of people who will use our inorganic arsenic assessment once it’s developed. We learned a lot from those conversations, including several things that will ultimately improve our assessment and make it more useful to the people who make decisions to protect public health. For example, we had initially planned to focus our assessment on oral exposures—the kind you might get from drinking water or eating food contaminated with inorganic arsenic. Based on the feedback we heard from others, we realized it was important to include information about the potential health effects of inhaling inorganic arsenic, too.  We were also reminded that providing information about those populations that may be more sensitive to the effects of inorganic arsenic is important to the users of the inorganic arsenic assessment.

We also learned that many people wanted to continue to have discussions on science issues that may inform the development of the assessment.  We agreed this was important, and in response started an arsenic webinar series.

To date we have held eight webinars on various topics relevant to assessing the human health risks of exposure to inorganic arsenic. For example, we held one webinar on inorganic arsenic and its potential effects on children’s neurodevelopment. We heard that the most sensitive endpoints to look at when examining the relationship between arsenic and children’s neurodevelopment are IQ and behavior.  We held another one on environmental justice issues related to inorganic arsenic. During that one, we heard about the importance of considering social stressors when looking at susceptibility.  This includes access to nutritional food, health care and prenatal care, and housing conditions.

I have really enjoyed holding these webinars. The talks have been informative, and it has been a great forum for discussion and input. I am happy to note that we are committed to engaging partners and public stakeholders throughout the development of the inorganic arsenic assessment. The next opportunity to provide feedback will be the upcoming IRIS June Bimonthly Public Meeting.

We have released several products for public input and discussion, including an assessment development plan, literature search, risk of bias evaluations for the studies under consideration, evidence tables, and some qualitative summary information about mode of action hypotheses (the chain of events that happens in the body after exposure to cause a health effect).

In addition, we will also be discussing key science issues relevant to assessing the health hazards of inorganic arsenic. A list of these issues is available on our website. We encourage you to help us identify additional science issues that you think are important.

These public discussions will ultimately help shape the science of our assessment. We hope you can join us for the conversation—your input could prove to be another terrific example of the power of teamwork!

About the author:  Janice Lee is a health scientist in EPA’s IRIS Program. She has been with EPA for the past seven years and has a Ph.D. in Environmental Health Sciences.

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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Is this Hazardous?


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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Science Wednesday: Continuously Strengthening our Science

Each week we write about the science behind environmental protection. Previous Science Wednesdays.

By Paul T. Anastas, Ph.D.

It is rigorous, cutting edge science that allows EPA to protect human health and the environment. Every decision and action that EPA takes on behalf of the American people is based upon it. Without science, effective pursuit of the Agency’s mission would be impossible.

Scientific work at EPA takes on many forms—tools, assessments, research, analysis, and monitoring are just a few. All of this work is continuously evolving to ensure we are always using the best science and latest insights. Yesterday, the Agency announced plans to make one of its most widely used science-based tools, the Integrated Risk Information System (IRIS), even stronger.

IRIS provides health profiles of over 500 chemicals and their potential impacts on human health. The system is publicly available and used by state and local governments, environmental specialists, healthcare professionals and international institutions to characterize the potential health effects of contaminant exposure.

In 2009, Administrator Lisa P. Jackson made significant changes to the IRIS process that vastly improved the timeliness of assessments. Since then, we’ve cut the average timeframe for completing assessments down from three plus years to 23 months and significantly reduced the backlog of assessments. In just two years, the staff dedicated to IRIS as well as funding for the program have increased by 25% and 50% respectively.

The changes announced yesterday focus on three areas of the IRIS program: accessibility of science, transparency of scientific rationale, and focused independent review. All new IRIS assessment documents will be shorter, clearer, and include more visuals and concise explanations of the rationale used to develop assessments and weigh scientific evidence. EPA will also publicly post references for all relevant studies and is working to set up a dedicated advisory committee that will focus on the quality, transparency and scientific rigor of IRIS assessments.

It is the responsibility of scientists to constantly seek out new information and insights from independent sources. Evaluating and incorporating these perspectives ensures that we always use the best science to most effectively pursue our mission. In this spirit, many of the new changes respond directly to suggestions from the National Academy of Science, a leading institution for independent scientific review.

The continuous improvement of IRIS reflects the natural evolution that accompanies all rigorous scientific work. Our continued ability to be agile—to evolve and incorporate new scientific insights—will be critical to pursuing our mission and protecting the American people.

About the author: Paul T. Anastas, Ph.D. is the Assistant Administrator for EPA’s Office of Research and Development.

Editor’s Note: The opinions expressed in Greenversations are those of the author. They do not reflect EPA policy, endorsement, or action, and EPA does not verify the accuracy or science of the contents of the blog.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action, and EPA does not verify the accuracy or science of the contents of the blog.

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.