Prenatal Chemical Exposures Linked to ADHD in Boys
New research conducted in New Bedford, Massachusetts suggests that organochlorine chemicals, which were first linked to learning problems in children more than two decades ago, may play a role in attention-deficit hyperactivity disorder (ADHD), especially in boys. Previous research has reported associations between organochlorines and ADHD-related behaviors, but this research found sex-specific effects in children born to mothers who lived near the contaminated harbor and dumpsites in low-income communities. This study adds to a growing body of literature associating learning disorders with prenatal chemical exposures.
According to the study, Neuropsychological Measures of Attention and Impulse Control among 8-Year-Old Children Exposed Prenatally to Organochlorines, boys who were exposed to higher levels of the organochlorines -polychlorinated biphenyls (PCBs) and DDE (a metabolite of DDT)- in the womb scored lower on focus and concentration tests, which indicates they are more likely to have attention problems often related to ADHD.
In the study, umbilical cord blood was collected from 788 newborns born between 1993 and 1998 from four towns near New Bedford Harbor, Mass., to see what they were exposed to in the womb. Roughly eight years after they were born, almost 600 of these children underwent two tests. One measured their ability to focus on and react to a specific target—in this case, the image of a cat on a computer screen- and to inhibit their response to another animal’s image. The other exam included parts of an IQ test that measured their processing speed and distractability, which tests whether they can maintain attention over time. Boys exposed to the highest levels of PCBs during their mother’s pregnancy failed to press a button for the on-screen cat 12 percent more often than children exposed to the lowest levels. Those same boys also scored slightly lower in the other test. The same link was not found in girls. Animal data suggest that hormone-disrupting chemicals, including PCBs, affect each gender differently, but the connection in humans remains unclear.
All of the children studied were born to mothers who lived near the contaminated harbor and dumpsites in low-income communities, where twice as many people live below the poverty line than the Massachusetts average. Unfortunately, children from low-income families are typically exposed to higher levels of environmental chemicals—some currently used and some long banned—than U.S. children from other socioeconomic backgrounds. The exposures in this New Bedford study were fairly low (median: 0.19ng/n PCB; 0.31ng/g DDE), which is comparable to children’s levels throughout much of the U.S. This means that a connection between PCBs and attention problems in boys could exist in other communities as well. Boys are two to three times as likely as girls to develop ADHD, the most common learning disorder reported in children worldwide. In 2007, U.S. parents reported that nearly 10 percent of children between the ages of 4 and 17 had been diagnosed with ADHD, according to the Centers for Disease Control and Prevention.
Banned in the U.S. more than 30 years ago, PCBs belong to the same class of chemicals as other notorious persistent pollutants, including DDT and chlordane. These chemicals persist in the environment for extraordinarily long periods of time and even accumulate in food chains. Nearly every U.S. resident still has detectable levels of an organochlorine chemicals in his or her blood. PCBs and its chemical cousins have the ability to disrupt hormones, which can alter how the brain develops. One study found a link between organochlorines and non-Hodgkin’s Lymphoma.
Organochlorines have previously been linked to a number of adverse effects on human health, including birth defects and diabetes. This study illustrates how the health impacts of pesticides are often long-term and multigenerational, with pesticides no longer in use continuing to affect public health. This also reinforces the need for a more precautionary approach to regulating pesticides and industrial chemicals. Once released into the environment, many chemicals can affect health for generations, either through persistence in the environment or long-term changes to the genetic code of humans and other animals.
In response to the growing evidence linking pesticide exposures to numerous human health effects, Beyond Pesticides launched the Pesticide-Induced Diseases Database to capture the range of diseases linked to pesticides through epidemiologic studies. The database, which currently contains hundreds of entries of epidemiologic and laboratory exposure studies, is continually updated to track the emerging findings and trends.
For more information, click here.
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Kevin T. Smiley
When hurricanes and other extreme storms unleash downpours like Tropical Storm Beta has been doing in the South, the floodwater doesn't always stay within the government's flood risk zones.
New research suggests that nearly twice as many properties are at risk from a 100-year flood today than the Federal Emergency Management Agency's flood maps indicate.
Flooding Outside the Zones<p>About <a href="https://furmancenter.org/files/Floodplain_PopulationBrief_12DEC2017.pdf" target="_blank">15 million</a> Americans live in FEMA's current 100-year flood zones. The designation warns them that their properties face a 1% risk of flooding in any given year. They must obtain flood insurance if they want a federally ensured loan – insurance that helps them recover from flooding.</p><p>In Greater Houston, however, <a href="https://doi.org/10.1111/j.1539-6924.2012.01840.x" target="_blank">47% of claims</a> made to FEMA across three decades before Hurricane Harvey were outside of the 100-year flood zones. Harris County, recognizing that FEMA flood maps don't capture the full risk, now <a href="https://www.hcfcd.org/floodinsurance" target="_blank" rel="noopener noreferrer">recommends that every household</a> in Houston and the rest of the county have flood insurance.</p><p>New risk models point to a similar conclusion: Flood risk in these areas outstrips expectations in the current FEMA flood maps.</p><p>One of those models, from the <a href="https://firststreet.org/flood-lab/research/2020-national-flood-risk-assessment-highlights/" target="_blank">First Street Foundation</a>, estimates that the number of properties at risk in a 100-year storm is 1.7 times higher than the FEMA maps suggest. Other <a href="https://doi.org/10.1088/1748-9326/aaac65" target="_blank" rel="noopener noreferrer">researchers</a> find an even higher margin, with 2.6 to 3.1 times more people exposed to serious flooding in a 100-year storm than FEMA estimates.</p>
What FEMA’s Flood Maps Miss<p>Understanding why areas outside the 100-year flood zones are flooding more often than the FEMA maps suggest involves larger social and environmental issues. Three reasons stand out.</p><p>First, some places rely on relatively old FEMA maps that don't account for recent urbanization.</p><p>Urbanization matters because impervious surfaces – think pavement and buildings – are not effective sponges like natural landscapes can be. Moreover, the process for updating floodplain maps is locally variable and can take years to complete. Famously, New York City was updating its maps when Hurricane Sandy hit in 2012 but hadn't finished, meaning flood maps in effect <a href="https://projects.propublica.org/nyc-flood/" target="_blank">were from 1983</a>. FEMA is required to assess whether updates are needed every five years, but the <a href="https://www.fema.gov/cis/nation.html" target="_blank" rel="noopener noreferrer">majority of maps</a> <a href="https://www.oig.dhs.gov/sites/default/files/assets/2017/OIG-17-110-Sep17.pdf" target="_blank" rel="noopener noreferrer">are older</a>.</p><p>Second, binary thinking can lead people to an underaccounting of risk, and that can mean communities fail to take steps that could protect a neighborhood from flooding. The logic goes: if I'm not in the 100-year floodplain, then I'm not at risk. Risk perception <a href="https://doi.org/10.1088/1748-9326/ab195a" target="_blank" rel="noopener noreferrer">research</a> backs this up. FEMA-delineated flood zones are the major factor shaping flood mitigation behaviors.</p><p>Third, the era of climate change scuttles conventional assumptions.</p><p>As the planet warms, extreme storms are becoming <a href="https://nca2018.globalchange.gov/" target="_blank">more common and severe</a>. If greenhouse gas emissions continue to increase at a high rate, computer models suggest that the chances of a severe storm dropping 20 inches of rain on Texas in any given year will increase from about 1% at the end of the last century to 18% at the end of this one, a chance of <a href="https://doi.org/10.1073/pnas.1716222114" target="_blank" rel="noopener noreferrer">once every 5.5 years</a>. So far, <a href="https://www.rstreet.org/wp-content/uploads/2020/02/195.pdf" target="_blank" rel="noopener noreferrer">FEMA hasn't taken into account the impact climate change is having</a> on extreme weather and sea level rise.</p>
Racial Disparities in Flooding Outside the Zones<p>So, who is at risk?</p><p>Years of research and evidence from storms have highlighted social inequalities in areas with a high risk of flooding. But most local governments have less understanding of the social and demographic composition of communities that experience flood impacts outside of flood zones.</p><p>In analyzing the damage from Hurricane Harvey in the Houston area, I found that <a href="https://doi.org/10.1088/1748-9326/aba0fe" target="_blank">Black and Hispanic residents disproportionately experienced flooding</a> in areas beyond FEMA's 100-year flood zones.</p><p>With the majority of flooding from Hurricane Harvey occurring outside of 100-year flood zones, this meant that the overall impact of Harvey was racially unequal too.</p><p>Research into where flooding occurs in Baltimore, Chicago and Phoenix points to some of the potential causes. <a href="https://www.nap.edu/read/25381/chapter/4#16" target="_blank" rel="noopener noreferrer">In Baltimore and Chicago</a>, for example, aging storm and sewer infrastructure, poor construction and insufficient efforts to mitigate flooding are part of the flooding problem in some predominantly Black neighborhoods.</p>
What Can Be Done About It<p>Better accounting for those three reasons could substantively improve risk assessments and help cities prioritize infrastructure improvements and flood mitigation projects in these at-risk neighborhoods.</p><p>For example, First Street Foundation's risk maps account for <a href="https://firststreet.org/flood-lab/research/flood-model-methodology_overview/" target="_blank">climate change</a> and present <a href="https://floodfactor.com/" target="_blank" rel="noopener noreferrer">ratings</a> on a scale from 1 to 10. FEMA, which works with communities to update flood maps, is <a href="https://www.fema.gov/media-library-data/1521054297905-ca85d066dddb84c975b165db653c9049/TMAC_2017_Annual_Report_Final508(v8)_03-12-2018.pdf" target="_blank" rel="noopener noreferrer">exploring rating systems</a>. And the National Academies of Sciences, Engineering and Medicine recently <a href="https://www.nationalacademies.org/news/2019/03/new-report-calls-for-different-approaches-to-predict-and-understand-urban-flooding" target="_blank" rel="noopener noreferrer">called for a new generation of flood maps</a> that takes climate change into account.</p><p>Including recent urbanization in those assessments will matter too, especially in fast-growing cities like Houston, where <a href="https://authors.elsevier.com/a/1boBRyDvMFW6W" target="_blank" rel="noopener noreferrer">386 new square miles</a> of impervious surfaces were created in the last 20 years. That's greater than the land area of New York City. New construction in one area can also <a href="https://scalawagmagazine.org/2018/01/city-in-a-swamp-as-houston-booms-its-flood-problems-are-only-getting-worse/" target="_blank" rel="noopener noreferrer">impact older neighborhoods downhill</a> during a flood, as some Houston communities discovered in Hurricane Harvey.</p><p>Improving risk assessments is needed not just to better prepare communities for major flood events, but also to prevent racial inequalities – in housing and beyond – from <a href="https://www.npr.org/2019/03/05/688786177/how-federal-disaster-money-favors-the-rich" target="_blank" rel="noopener noreferrer">growing</a> after the unequal impacts of disasters.</p>
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