Prenatal Exposure to Air Pollution Associated with Higher Risk for Autism-related Outcomes, ECHO Study Finds
Author(s): Heather Volk, Akhgar Ghassabian, et al.
Who sponsored this study?
The Environmental influences on Child Health Outcomes (ECHO) Program, Office of the Director, National Institutes of Health supported this research.
Why was this study needed?
Air pollution is a significant environmental health concern and contributes to many illnesses and early deaths worldwide. Ambient air pollution can have detectable effects on the brain. Recent studies show that being exposed to air pollution during pregnancy and early life can affect how a child’s brain develops. This can happen through several pathways, such as causing inflammation in the brain, disrupting hormones, or changing how genes work. Previous research has suggested potential links between air pollution and neurodevelopmental disorders, but the relationship between exposure to air pollution, even at low levels, during pregnancy and ASD has been unclear. This study examined the associations between prenatal air pollution exposure and autism spectrum disorder (ASD) in children.
What were the study results?
The study team observed that higher prenatal exposure to ozone was associated with autism-related traits and increased risk of ASD diagnosis. Exposure to fine particulate matter (PM2.5) and nitrogen dioxide was also associated with a higher risk of autism, but associations varied by geographical regions. There was little evidence for differences between boys and girls in the association between prenatal air pollution exposure and autism outcomes.
Footnote: Results reported here are for a single study. Other or future studies may provide new information or different results. You should not make changes to your health without first consulting your healthcare professional.
What was the study's impact?
The study's findings suggest that even low levels of air pollution exposure during pregnancy might be associated with autism-related outcomes. This highlights the importance of understanding the risks associated with air pollution exposure during pregnancy and its effects on child neurodevelopment.
Who was involved?
The study involved 8,035 mother-child pairs from 44 ECHO study sites across the United States. This sample included over 1,000 child participants who were potentially at higher risk for ASD due to being born preterm or having siblings with autism. The remaining participants were recruited from samples representative of the general population.
What happened during the study?
This study looked at scores from the Social Responsiveness Scale (SRS), a parent-report tool that measures autism-related traits in children, with higher scores indicating higher autism-related traits. During the study, researchers estimated daily exposure to particulate matter, nitrogen dioxide, and ozone at the residential addresses of pregnant women. They then analyzed the associations between these air pollutants and autism-related traits using the Social Responsiveness Scale (SRS) and physician-diagnosed ASD.
What happens next?
The study results suggest that even small changes in prenatal air pollution exposure could have a significant impact on child neurodevelopment. Future studies are needed to understand why these connections exist and to look at the impact of specific air pollution components.
Where can I learn more?
Access the full journal article, titled “Prenatal Air Pollution Exposure and Autism Spectrum Disorder in the ECHO Consortium,” in Environmental Health Perspectives.
The content is the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
ECHO Study Investigates Pollution Exposure and Birth Outcomes in Pregnant Women Living in Historically Redlined Neighborhoods
Authors: Teresa Herrera, Akhgar Ghassabian, et al.
Who sponsored this study?
The Environmental influences on Child Health Outcomes (ECHO) Program, Office of the Director, National Institutes of Health supported this research.
Why was this study needed?
Exposure to tiny air pollutants known as PM2.5 during pregnancy can lead to outcomes like low birth weight and preterm birth. Factors such as weather, government policies, and social conditions can affect how much exposure pregnant women have to these pollutants. One factor that may have affected exposure is redlining, the historical practice of designating certain neighborhoods, often where minority groups lived, as risky investments for lenders. This grading system ranked neighborhoods on an A through D scale—A being the most desirable—which often led to disinvestment and lack of resources in lower-rated areas. While redlining was made illegal following the 1968 Fair Housing Act, it continues to affect the health outcomes of people living in historically redlined areas.
ECHO researchers wanted to learn whether living in historically redlined areas during pregnancy affects air pollution exposure and birth outcomes in New York City (NYC). Understanding what influences PM2.5 levels and their impact on birth outcomes can help improve the health of mothers and their children.
What were the study results?
The study found that living in lower-graded or ungraded census tracts during pregnancy was associated with higher exposure to PM2.5. These women also tended to have babies with lower birth weights. This association was strong even when considering factors such as race, ethnicity, and income at individual and community levels.
What was this study's impact?
The study supports the literature linking redlining to contemporary outcomes. This study highlights the multifaceted nature of structural racism. Findings from non-graded areas indicate that there are likely additional factors, along with redlining, that play a role in perpetuating modern-day inequality.
Who was involved?
The participants were 3,160 pregnant mothers and their babies in the NYC metropolitan area who were enrolled in six ECHO Cohort research sites. The study included pregnant mothers from 2005 to 2022 who had air pollution estimates available for their residential address. Most participants who identified as Black or White lived in neighborhoods that had been given a D grade, the lowest rating. Most participants who identified as Hispanic lived in neighborhoods with B or C grades.
What happened during the study?
Researchers used statistical methods to explore whether living in neighborhoods that were historically redlined was associated with higher exposure to air pollution (PM2.5) during pregnancy. They also examined if living in these neighborhoods was associated with the baby's birth weight, the likelihood of being born early, and the chances of having a low birth weight.
Note: Results reported here are for a single study. Other or future studies may provide new information or different results. You should not make changes to your health without first consulting your healthcare professional.
What happens next?
The authors note that future research could look at other practices like racial exclusionary zoning to fully understand the ongoing systemic effects of redlining.
Where can I learn more?
Access the full journal article, titled “Redlining in New York City: Impacts on Particulate Matter Exposure During Pregnancy and Birth Outcomes,” in Journal of Epidemiology and Community Health.
The content is the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
ECHO Study Suggests Air Pollution, Secondhand Smoke, Formaldehyde Exposure Affect Length of Time to Get Pregnant
Author(s): Eva Siegel, Linda Kahn, et al.
Who sponsored this study?
This research was supported by the Environmental influences on Child Health Outcomes (ECHO) program, the Office of the Director, the National Institutes of Health, with co-funding from the Office of Behavioral and Social Sciences Research (OBSSR).
What were the study results?
The strongest evidence points to an association between exposures to traffic-related air pollution, secondhand smoke, and a chemical called formaldehyde—a common workplace exposure in construction sites and nail salons—and longer time to pregnancy. Specifically, exposure to particulate matter and nitrogen oxide gases lowered couples’ chances of becoming pregnant. Traffic and the burning of other types of materials besides gas and diesel create particulate matter and nitrogen oxide gases. Volatile organic compounds, which are used in manufacturing processes, did not appear to affect time to pregnancy.
What was the study's impact?
This review suggests that certain chemicals in the air may lengthen the time it takes for couples to become pregnant. More research is needed to better understand how these chemicals affect reproductive health. To collect this information, future studies can provide participants with personal air monitors that can let researchers know about the quality of air participants are actually breathing instead of relying on imprecise data from outdoor monitors or participant recall.
The research team also pointed out that there are remaining questions about whether the air people breathe around the time of conception is what matters most or whether there are certain life stages, such as puberty, when being exposed to air pollution may be especially damaging. The ECHO-wide Cohort, which allows researchers to access information from a large and diverse population, can serve as an important resource for answering these questions.
Why was this study needed?
Previous studies have looked at how air pollution may affect how long it takes to become pregnant. Time to pregnancy is a measure used to estimate a couple’s ability to conceive and is commonly used to diagnose infertility. In this paper, the authors review past studies on air pollution to identify types of air pollutants—including pollution from traffic, chemicals in the workplace, and secondhand smoke—that might affect how long it takes to get pregnant.
Who was involved?
This review includes all papers published in English on this topic from January 1, 1990 to February 11, 2021. The analysis covered 33 articles, of which eight looked at outdoor air quality, six looked at secondhand smoke exposure, and 19 looked at air quality in the workplace.
What happened during the study?
The research team searched six leading science libraries and identified 33 human studies related to exposure to outdoor and indoor air pollutants and time to pregnancy. The team read each article, assigned it a score based on the quality of the study design, and created summary tables containing the most important findings of each study. They then compared the consistency of results between studies, especially among high-quality papers, about whether certain types of air pollution affected time to pregnancy.
What happens next?
This is the third review this team of authors has written on chemicals and time to pregnancy. Individual authors will continue to fill in the research gaps previously mentioned, including conducting studies where women will be wearing personal air monitors.
Where can I learn more?
Access the full journal article, titled “Indoor and outdoor air pollution and couple fecundability: a systematic review” in Human Reproduction Update.
The content is the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
ECHO Review Finds Air Pollution May Be Associated with Child Brain Development, Behavior
Author(s): Heather E. Volk, Frederica Perera, Joseph M. Braun, Samantha L. Kingsley, Kim Gray, Jessie Buckley, Jane E. Clougherty, Lisa A. Croen, Brenda Eskenazi, Megan Herting, Allan C. Just, Itai Kloog, Amy Margolis, Leslie A. McClure, Rachel Miller, Sarah Levine, Rosalind Wright
Who sponsored this study?
This research was supported by the Environmental influences on Child Health Outcomes (ECHO) Program, Office of The Director, National Institutes of Health.
What were the study results?
ECHO provides a unique opportunity to study how air pollution can affect children’s brain development and behavior in a large, diverse study population. It also has the ability to study pollutant exposures by geographic area, which has been a limitation in previous research.
What was the study's impact?
This study sets up the possibility of future work in ECHO on the effect of prenatal air pollution exposure on brain development in children.
Why was this study needed?
This study summarized information on different ways to measure prenatal air pollution exposure and what we know about how air pollution affects children’s behavior and brain development. It also helps create a plan for ECHO to study how being exposed to air pollution in the womb may affect children’s behavior.
Who was involved?
This paper uses summary data from ECHO to learn if there may be enough participants in the future to study how air pollution can affect children’s brain development and behavior.
What happened during the study?
Researchers reviewed earlier papers on air pollution and child development to summarize what those studies found. Then, they used that information to develop a plan that ECHO might use to fill gaps in that earlier work to advance children’s health.
What happens next?
Future studies will do the work described here – to examine air pollution exposure in ECHO participants by geographic area to determine how air pollution can affect the brain.
Where can I learn more?
Access the full journal article, titled “Prenatal air pollution exposure and neurodevelopment: A review and blueprint for a harmonized approach within ECHO.”
The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Working with Rural Communities to Improve Household Air Quality and Health: Strategies to Guide Environmental Interventions in the ECHO IDeA States Pediatric Clinical Trials Network
Speakers:
Ros Singleton, MD, MPH; Alaska Native Tribal Health Consortium, Anchorage
Speaker Bio: Rosalyn Singleton graduated from Northwestern University Medical School, Chicago and completed a Pediatric residency and MPH. She initially worked as a pediatrician in a Navajo hospital. Since 1988 she has worked as a pediatrician, immunization consultant and researcher for Alaska Native Tribal Health Consortium, and guest researcher at Arctic Investigations Program – CDC. Ros has worked with Alaska Native people on clinical studies related to vaccine preventable infections, respiratory infections, vitamin D deficiency, indoor air quality and bronchiectasis.
Erin Semmens, PhD, MPH; University of Montana
Speaker Bio: Erin Semmens graduated with a degree in Biology and Political Science from Duke University and received an MPH in Environmental and Occupational Health and a PhD in Epidemiology from the University of Washington. She is an Assistant Professor of Epidemiology in the School of Public and Community Health Sciences at the University of Montana. Erin’s research investigates the effects of environmental and occupational factors– and more recently their interaction with social influences– on long-term health. Specifically, she focuses on the health impacts of air pollution from multiple sources including wildfires, wood smoke, and traffic.
Q: I would like to know the hypotheses that link those special populations, including Alaskan Natives, to a prevalence of bronchiectasis?
Ros Singleton: It is clear in collaborations with Australia and New Zealand and Canada and other researchers on bronchiectasis that this orphan disease is prevalent in these populations because of environmental and social factors. We did a three country analysis and discovered that household crowding was one of the most prevalent common factors. In Alaska lack of running water, and in Australia access to basic household features like a working refrigerator and a working sink, are the factors that are associated with both pneumonia and childhood pneumonia, which is the driver of bronchiectasis. Bronchiectasis was common in many other populations around the world until vaccines and improvements in running water and basic public health measures have really reduced that risk around the world. But it is still prevalent in much of the developing world and low income countries, although rarely identified because CT scans are not available. We have identified very high rates in many different indigenous populations.
Q: Indoor PM2.5 did not decrease after intervention, was it possible that PM2.5 from outdoors and neighboring houses played a role and that is why you do not see the decreased PM2.5?
Ros Singleton: I don’t think that is a major factor based on the feedback that we received from the environmental health specialist. It is possible that in a time when there is a lot of wood burning that you could have ambient 2.5 that comes in and so that could be a factor. Many of these homes are on a very windy tundra so that ambient 2.5 level is not very high in general, but we don’t have the data to prove that so that is one possibility. I think one other major thing that we identified was just the challenges for accessing dry wood. You have to find dry wood and in many areas there is no wood available and so people use driftwood and sometimes unfortunately trash. My colleagues have done a lot of education around the best practices in wood burning, and that’s why I’m excited about this new potential project in incorporating indigenous knowledge and really coming together to determine what are the best things to burn and how to burn so that it is most efficient and has the lowest PM2.5.
Q: How prevalent is secondary cigarette exposures in the studies described today? Has smoking cessation education been combined with indoor air quality interventions discussed today?
Erin Semmens: In the ARTIS study we excluded homes where there was an active smoker in the home, and in our ongoing study we did not make that exclusion because we thought that would exclude too many families. We don’t include smoking cessation as part of the education. We do nicotine wipes in the home as an indicator of whether there is smoking inside the home. I can say from looking at Montana birth certificate data that about 15% of women report smoking during pregnancy which is likely an underestimate, but still fairly high.
Ros Singleton: In Alaska, smoking rates are very high among Alaskan native people. Over 40% of adults smoke, as compared to about 20% in other populations. In Navajo smoking is actually very rare. In our study we did do tobacco cessation education and there are major tobacco cessation projects underway in Alaskan Native communities in collaboration with Mayo Clinic, and specifically with pregnant women because the rate of tobacco use including both smoking and also chew is extremely prevalent and smoking cessation is challenging. However, the homes in this study, as well as homes of families that have children hospitalized, have told us for many years that they do not smoke in the home. I believe that household education has really hit on fertile ground and people do understand the message about not smoking indoors. But smoking itself is very prevalent.
Q: In our region (South Dakota), many of our families are pretty mobile between seasons. Is this a common occurrence in your region? If so, how did you handle this in the analysis?
Ros Singleton: In our smaller study, we did have one family withdraw because of moving, but in general we were able to work with families that were there for the year. Moving is very common and that was a challenge. One family was actually living in a Conex (shipping container) at the initial part of the study and then had other housing.
Erin Semmens: Moving has been a challenge in our study, so when we provide potential participants with information about the study, we ask if they plan to be in the same home over the next two years. So to be in the study they have to plan to be stable with respect to their residence, but that isn’t always the case. That is the primary reason participants drop out of the study is because they move and when we are utilizing interventions that are aimed at improving indoor air quality it is very difficult when a person moves to a different home, even if it is another home with a wood stove to compare that. Unfortunately that has resulted in lost to follow-up or participants withdrawing from the study due to moving. A somewhat related point is when children spend part of their time during the week with one parent and part of the time with another parent. In those cases the child can be in the study, but we just do all of our sampling at the one residence.
Q: Did the stove change-out help decrease particulate matter?
Ros Singleton: In our first study, even with education we did not show a decrease in PM2.5. We did show a decrease in volatile organic compounds and we actually added volatile organic compounds late, but we found that it is a significant contributor to some aspects of indoor air pollution. In our region houses are small and villages often do not have a workshop available, and so the home is often used as a workshop and it is not unusual to have a father that is working on a snow machine or snow mobile inside the house. Also because of the cold temperatures, fuel is often stored in the house and people try to store it in the artic entry way but that is another potential source of volatile organic compounds. So we have some unusual sources of volatile organic compounds and we did some education around that.
Erin Semmens: In the Libby change-out there was a decrease in ambient PM2.5, which is a huge achievement, and it was such a large scale change-out. 1200 wood stoves and the population of Libby is under 3000 people, so that was a very large scale change-out in that community. But within the homes, indoor air quality reductions varied from home to home and the reason we hypothesized that there weren’t universal reductions is just having the new cleaner burning wood stove is not sufficient and that there are all these other best burning practices and education around how to use the wood stove that are needed as well. Another consideration is that people with new wood stoves might end up using their new stoves more.
Ros Singleton: In a pre-study home visit, the healthy home specialist said that the house was so smoky you could hardly see across the room. Obviously if you have a wood stove that is that bad and you have an alternative like a Toyo stove you are going to use the Toyo stove, but then if you get a great new wood stove that is much more efficient than you will probably revert to using the wood stove. That is one of our hypotheses, that no matter what you do to a wood stove it still has more PM2.5 than not using a wood stove. So if the use of the wood stove increase, then your PM2.5 may increase just because of that.
Q: I’m curious about your comments about best burn practices. What are people burning, what were they burning and talk more about best burn practices?
Ros Singleton: What you burn is so critical and like I mentioned a lot of the houses in Alaska are in non-treed areas. People burn driftwood and you have to leave driftwood for a long time for it to become dried, and by default people often use wet wood and burn wood that is wet. The wetter it is then the more inefficiently it burns and you have higher PM2.5 gas and other things. What you burn is critical. If you burn trash you can imagine what is in newspaper print and other things. There are all kinds of volatile compounds that are in trash and in other paper products that may have plastic also. Sometimes families revert to burning trash because that is what they have available. There has been many efforts to try to improve this. One effort is education on stacking and drying wood, and the emphasis on using only wood. There are also some very innovative projects that provide very efficient pellets. We’ve received feedback from some of those, but unfortunately it is pretty expensive to have them shipped up to Alaska so we haven’t done that intervention yet.
Erin Semmens: Having dry wood is not always available even if you live in a place like Montana that has a lot of trees and a lot of wood available, you may not have dry wood available. One of the main factors we saw in our pre-intervention year in the ARTIS study was that letting your wood dry out for a year or more was associated with lower PM2.5 concentrations, so it is a really important feature of best burning practices. In one community in a different study taking place in Idaho that tries to address that by having a community-level intervention with a community wood yard where the wood is stored properly and in season for the recommended length of time and then distributed to elders living in the community to provide them with access to dry wood. That is one way to try and address that challenge.
Q: I wanted to know more details about the air filtration device used in their study. Erin says it was a 3M electrostatic precipitator but I was interested in knowing more details about this device such as model and how they were maintained in the study. The info would help me understand why they did not observe reductions in PM2.5.
Erin Semmens: We used a large 3M filtrate with an electrostatic filter. We recommended that homes run the filter continuously on the highest setting, and we saw substantial reductions (nearly 70% greater than those observed in the placebo arm) from the pre- to post-intervention winter. We replaced the filter approximately once per month. It was the wood stove change-out arm, in which we did not see significant reductions in PM2.5 from the pre- to post-intervention winter.
Q: Have insulation in the homes had been investigated?
Ros Singleton: For Alaska studies – In general, the houses are insulated and tend to be tight homes for heating efficiency which can exacerbate indoor air pollution. For the most part, homes for our study had already had insulation evaluated through weatherization programs.
Erin Semmens: That is a great question and reminds me that we did blower door tests in the ARTIS study to evaluate airtightness. I recall we had a wide range of values but I am not sure if or to what degree home tightness varied between treatment arms. Theoretically, it should have balanced out, but I would need to look back to see if it actually did.
Ros Singleton, MD, MPH; Alaska Native Tribal Health Consortium, Anchorage 
Erin Semmens, PhD, MPH; University of Montana