written by Laura N. Vandenberg, PhD
Assistant Professor and Graduate Program Director of Environmental Health Sciences, University of Massachusetts Amherst School of Public Health and Health Sciences
Laura Vandenberg (Credit: umass.edu)
Reprinted with permission from Environmental Health News
Cancer. Diabetes. Autism. Infertility. ADHD. Asthma. As the rates of these diseases increase over time, the public and researchers alike have focused on the role the environment might play in their cause and progression. Scientists in the field of environmental health sciences are not satisfied just to know that the environment contributes to human disease – they want to know how.
This week [ScienceSeptember 18-20], researchers, public health advocates, government officials, and industry spokespersons will meet at National Institutes of Health (NIH) to celebrate 25 years of scientific research on one aspect of environmental health: endocrine disrupting chemicals (EDCs). These are compounds that alter the way hormones act in the body, often by mimicking or blocking their actions. Just a few examples of widely used consumer products that contain EDCs are plastics, electronics, flooring, some personal care products, and furniture treated with some flame retardants.
We present CHE’s picks of the most important environmental health stories from the last quarter of 2014.
- Air pollution and autism
A growing body of evidence implicates air toxics as potential contributors to autism spectrum disorders, with four studies published in rapid succession this quarter:
- Environmental chemical exposures and autism spectrum disorders: a review of the epidemiological evidence.
- University of Pittsburgh study correlates autism with air pollution: Preliminary results from the study show that children with autism spectrum disorders were more likely to have been exposed to higher levels of certain air toxics during their mothers’ pregnancies and their first two years of life compared with children without the condition. The study: The association of national air toxics assessment exposures and the risk of childhood autism spectrum disorder: a case control study.
- Air pollution exposure in pregnancy linked to autism in study: Women who are exposed to high levels of air pollution during their third trimester of pregnancy may be twice as likely to have an autistic child. The study: Autism spectrum disorder and particulate matter air pollution before, during, and after pregnancy: a nested case–control analysis within the Nurses’ Health Study II cohort.
- Fourth study finds traffic pollution may cause autism: The more traffic pollution a pregnant woman is exposed to — especially during her third trimester — the greater chance her child will develop autism. The study: In utero exposure to toxic air pollutants and risk of childhood autism.
- Phthalates’ effects on health
A proposed rule by the Consumer Product Safety Commission was mandated by the Consumer Product Safety Improvement Act of 2008 and is now open for public comment: Prohibition of children’s toys and child care articles containing specified phthalates. Research continues to bring fuller understanding of the potential for harm from several phthalates:
- Prenatal exposure to household chemical linked to reduced IQ, study says: Children who were exposed in utero to high levels of phthalates went on to have lower IQ levels than their peers who were exposed to lower levels, a new study from the Mailman School of Public Health at Columbia University found. The study: Persistent associations between maternal prenatal exposure to phthalates on child IQ at age 7 years.
- A birth cohort study to investigate the association between prenatal phthalate and bisphenol A exposures and fetal markers of metabolic dysfunction: Associations between maternal exposure to chemicals and markers of metabolic function appear potentially to be sex specific.
- Plastics chemical linked to changes in boys’ genitals: Boys exposed in the womb to high levels of a chemical found in vinyl products are born with slightly altered genital development, according to research published today. The study of nearly 200 Swedish babies is the first to link the chemical di-isononyl phthalate (DiNP) to changes in the development of the human male reproductive tract. The study: Prenatal phthalate exposures and anogenital distance in Swedish boys.
- How household plastics could ruin your sex life: Phthalates are being linked to, among other things, a decrease in libido in women. The study: Environmental exposure to di-2-ethylhexyl phthalate is associated with low interest in sexual activity in premenopausal women.
- Sugar and other sweeteners
The impact of sugar and other sweeteners on health has been getting more attention lately. In addition to the launch of SugarScience, a new website touted as an authoritative source for evidence-based, scientific information about sugar and its impact on health, the nation’s first soda tax passed in Berkeley, California. Proponents of the tax say it will curb the consumption of sodas, energy drinks and sweetened teas which are contributing to the country’s obesity epidemic and Type 2 diabetes. Meanwhile, research is uncovering health effects of sugar and other sweeteners that go beyond obesity and diabetes:
- This is your teenager’s brain on soda: Researchers at the University of Southern California recently published a study showing a connection between sugar consumption and memory problems. The study: Effects of sucrose and high fructose corn syrup consumption on spatial memory function and hippocampal neuroinflammation in adolescent rats.
- Intake of energy-dense foods, fast foods, sugary drinks, and breast cancer risk in African American and European American women.
- Soda and cell aging: associations between sugar-sweetened beverage consumption and leukocyte telomere length in healthy adults from the National Health and Nutrition Examination Surveys.
- Climate change
The biggest climate story this quarter was that the US and China announced important new actions to reduce carbon pollution. The Climate Change 2014: Synthesis Report from the Intergovernmental Panel on Climate Change also reiterated that the situation requires immediate and substantial action or the Earth will face “further warming and long-lasting changes in all components of the climate system, increasing the likelihood of severe, pervasive and irreversible impacts for people and ecosystems.” While the connection to human health is not always mentioned in reports on climate change, the health impacts are substantial. For example, in Chemically mediated behavior of recruiting corals and fishes: a tipping point that may limit reef recovery, there’s an understated repercussion of the loss of reefs: devastating impacts on sources of food, and especially protein, for much of the world’s human population. Other stories highlighting other aspects of climate change include these:
- From bar fights to wars, climate change will make us more violent: The hotter it gets, the more likely we are to kill each other. Murder rates go up in heat waves; in some countries, civil war is also more likely. In training exercises in hot weather, police are more likely to pull out a gun and fire. The paper: Climate and conflict.
- Climate change affects national security: After close examination of the science, the Military Advisory Board, a group of 16 retired flag-level officers, conclude that, “The national security risks of projected climate change are as serious as any challenges we have faced.”
- NY health and environmental chiefs: no to fracking
New York Governor Andrew Cuomo’s administration has moved to prohibit fracking in the state, citing unresolved health issues and dubious economic benefits of the widely used gas-drilling technique. This is the first US state to take such a stand. The report from the New York State Department of Health: A Public Health Review of High Volume Hydraulic Fracturing for Shale Gas Development and another recent report: Warning Signs: Toxic Air Pollution Identified at Oil and Gas Sites.
- BPA and its replacements
While more research mounts on health concerns from exposure to BPA, the Food and Drug Administration maintains that “the available information continues to support the safety of BPA for the currently approved uses in food containers and packaging”, as reported in Bisphenol A is safe for approved uses in food containers, packaging, FDA says. In a conflicting decision, a California court upheld the state scientists’ finding that BPA is known to cause reproductive health problems: Court upholds BPA health warning. Recent research on BPA and replacements include these studies:
- Kids exposed to BPA before birth at risk of wheeze: study: Young kids who were exposed to Bisphenol A before birth are more likely than others to have a wheeze before age five, according to a new study that found no connection to BPA exposure after birth.The study: Bisphenol A exposure and the development of wheeze and lung function in children through age 5 years.
- Prenatal bisphenol A exposure and maternally reported behavior in boys and girls: These results suggest that prenatal exposure to BPA may be related to increased behavior problems in school age boys, but not girls.
- The leaching of BPA into skin from cash receipts is enhanced by using sanitizers: Touching cash register receipts while using sanitizers can dramatically increase your body’s absorption of BPA, researchers report. The study: Holding thermal receipt paper and eating food after using hand sanitizer results in high serum bioactive and urine total levels of bisphenol A (BPA).
- BPA exposure by infants may increase later risk of food intolerance: This research involving rats suggests that early life exposure at a dose significantly below the current human safety limit set by the FDA affects developing immune systems, predisposing offspring to food intolerance in adulthood. The study: Food intolerance at adulthood after perinatal exposure to the endocrine disruptor bisphenol A.
- That takeout coffee cup may be messing with your hormones: A new study suggests that whole classes of BPA-free plastics — including the kind in styrofoam — release estrogenic chemicals. The study: Estrogenic chemicals often leach from BPA-free plastic products that are replacements for BPA-containing polycarbonate products.
- New study charts the fate of chemicals affecting health and the environment
In a new study, Rolf Halden, PhD, a researcher at Arizona State University’s Biodesign Institute, examines the trajectory of chemicals appearing as emergent threats to human or environmental health. His research offers a highly instructive analysis of how long it takes chemicals of concern to become recognized and acted on — and why. The review: Epistemology of contaminants of emerging concern and literature meta-analysis.
- 16 major companies and agencies say no to chemical flame retardants
The Center for Environmental Health, which helped encourage a rewrite of California’s regulations regarding safety standards in furniture manufacturing, announced in mid December that 16 major furniture manufacturers have now “sworn off” chemical flame retardants. This is a prime example of how environmental health science can be effectively translated into regulations that better protect health. The CEH press release including the list: Major producers eliminating flame retardant chemicals as major buyers are demanding flame retardant-free furniture.
- National Institutes of Health ends longitudinal children’s study
The US National Institutes of Health has cancelled its plan for an ambitious, multi-decade study of environmental influences on children’s health known as the National Children’s Study, agency director Francis Collins announced on December 12th. The study was originally approved by a bipartisan Congress in 2000 but was fraught with scientific and political challenges over the last 14 years. See also an analysis: How the US government botched its multibillion-dollar plan to beat childhood disease.
- Theo Colborn: Honoring the work of an environmental health giant
Theo Colborn, PhD, passed away on December 14th at age 87, leaving an extraordinary legacy of careful and determined environmental health research and advocacy. She was particularly recognized for her seminal work on endocrine disrupting chemicals and fracking.
- A brief biography by Elizabeth Grossman.
- Theo’s CV.
- Comments and stories from those who knew Theo.
- Remembering the genius who got BPA out of your water bottles, and so much more, one of many media reports on Theo’s death.
written by Martha Herbert, PhD, MD
This excerpt from Dr. Herbert’s blog is shared with her permission. Read the full post on her blog.
The recent New England Journal of Medicine paper by Stoner and colleagues, “Patches of disorganization in the neocortex of children with autism.” N Engl J Med 370(13): 1209-1219, made several important contributions to studies of postmortem tissue samples from the brains of individuals with autism spectrum disorders (ASDs). First, the average age was much younger than the average age in previous studies. Second, many important and technologically sophisticated measures were made. Finally, as a result of this work, a broadly distributed pattern of brain tissue abnormalities was identified that had not been described on this scale before—namely, patches of disorganization in many areas of the neocortex (the outer layer of gray matter in the brain), though not the same from one person to the next.
The new observation of disorganized patches by itself is very important. It poses an important challenge: how do we figure out what it means? To do that, we need to understand the data, and also to examine the interpretations and consider alternative possibilities.
Continue reading on Dr. Herbert’s site.
These are the environmental health stories, studies and reports that we think are most significant from the last three months. Comments are invited.
- Global toll of pollution on health
The scope and depth of pollution worldwide and its significant toll on health and lifespan is underscored in these new reports.
- WHO: Air pollution top environmental health risk: Air pollution kills about 7 million people worldwide every year and is now the single biggest environmental health risk, with more than half the fatalities due to fumes from indoor stoves. The study: 7 million premature deaths annually linked to air pollution.
- In developing world, pollution kills more than disease: Pollution, not infectious disease, is the biggest killer in the developing world, taking the lives of more than 8.4 million people each year, a new analysis shows. However, pollution receives a fraction of the interest from the global community. A related report: The Poisoned Poor: Toxic Chemicals Exposures in Low- and Middle-Income Countries.
- China and India face huge cancer burden: experts: China and India are facing a cancer crisis. Sixty percent of cancer cases in China are attributable to “modifiable environmental factors”, including smoking, water contamination and air pollution, a new report concludes. The report: Challenges to effective cancer control in China, India, and Russia
- Economic costs of pollution
It’s difficult to ignore these numbers and impacts, even for those not personally touched by disease or disability.
- Health costs of China’s polluted air ‘up to $300 bn a year’: Premature deaths and health problems from air pollution cost China as much as $300 billion a year, an official report said, calling for a new urbanisation model for the world’s second-largest economy.
- Health costs of air pollution from agriculture clarified: Computer models, including a NASA model of chemical reactions in the atmosphere, were used to better represent how ammonia interacts in the atmosphere to form harmful particulate matter. The study: Hidden cost of US agricultural exports: particulate matter from ammonia emissions.
- The full “costs” of environmentally related disease: What do failed attempts at environmental protection cost us, in terms as wide-ranging as health impacts, lost wages, and loss of IQ? Who is most burdened by our lack of societal commitment to primary prevention? The Environmental Health Policy Institute examines these questions through the lens of important cases.
- Health costs in the EU—how much is related to EDCs? Exposure to food and everyday electronic, cosmetic and plastic products containing endocrine disrupting chemicals (EDCs) may be costing up to €31 billion per year in the EU. Also Economic benefits of tighter controls for endocrine disruptors outweigh hypothetical trade effects.
- Lead poisoning of children in Michigan costs $330 million per year: Four main categories of impact were studied and expenditures were projected for costs associated with lead contamination of children: increased health care, increased adult and juvenile crime, increased need for special education, and decline in lifetime earnings.
- Measuring the economic cost of environmental impacts on human health: 25 experts in air quality, health economics and environmental sciences as well as representatives of EU agencies and the civil society met in Berlin, Germany, to assess this cost and guide policy makers in reducing it by investing in prevention.
- Air pollution is a $1.7T health problem, OECD finds: In the 34 OECD member states, the monetary impact of death and illness due to outdoor air pollution was $1.7 trillion in 2010. Research suggests that motorized on-road transport accounts for about 50 percent of that cost. The report: The cost of air pollution: health impacts of road transport.
- Improving air quality in NYC would boost children’s future earnings by increasing IQ: The study is the first to estimate the costs of IQ loss associated with exposure to air pollution, and is based on prior research on prenatal exposure to air pollutants among low-income children. The study: Prenatal exposure to airborne polycyclic aromatic hydrocarbons and IQ: estimated benefit of pollution reduction.
- Role of environmental influences on autism
Research continues to reveal the contribution of environment to autism spectrum disorders.
- Autism risk higher near pesticide-treated fields, study says: Babies whose moms lived within a mile of crops treated with widely used pesticides were more likely to develop autism, according to new research. The study: Neurodevelopmental disorders and prenatal residential proximity to agricultural pesticides: the CHARGE Study.
- Environment as influential as genes in autism, study says: Environmental factors are more important than previously thought in leading to autism, as big a factor as genes, according to the largest analysis to date to look at how the brain disorder runs in families. The study: The familial risk of autism.
- Environmental influences may cause autism in some cases, study shows: The findings shed light on why older mothers are at increased risk for having children with ASD and could pave the way for more research into the role of environment on ASD. The study: Mosaic epigenetic dysregulation of ectodermal cells in autism spectrum disorder.
- The scent of a man: gender of experimenter has big impact on rats’ stress levels, explains lack of replication of some findings
Scientists’ inability to replicate research findings using mice and rats has contributed to mounting concern over the reliability of such studies. Now, an international team of pain researchers led by scientists at McGill University in Montreal may have uncovered one important factor behind this vexing problem: the gender of the experimenters has a big impact on the stress levels of rodents, which are widely used in preclinical studies. The study: Olfactory exposure to males, including men, causes stress and related analgesia in rodents. The validity of the scientific processes and the results produced must be examined if we are to rely on scientific investigation to guide policy.
- Stress and health
Stress as an environmental health issue, and how it interacts with other environmental factors, provides insights into the complexity of health. The transgenerational concerns are notable.
- Sperm RNA carries marks of trauma: A study finds that stress in early life alters the production of small RNAs, called microRNAs, in the sperm of mice. The mice show depressive behaviors that persist in their progeny, which also show glitches in metabolism. The study: Implication of sperm RNAs in transgenerational inheritance of the effects of early trauma in mice.
- Chronic stress heightens vulnerability to diet-related metabolic risk: Highly stressed people who eat a lot of high-fat, high-sugar food are more prone to health risks than low-stress people who eat the same amount of unhealthy food. The study: Chronic stress increases vulnerability to diet-related abdominal fat, oxidative stress, and metabolic risk. See also New insights into chronic stress, obesity, and metabolic syndrome: further support for an ecological model of health and an integrated approach to care for more analysis.
- Childhood bullying involvement predicts low-grade systemic inflammation into adulthood: Although C-reactive protein (CRP) levels rose for all participants from childhood into adulthood, being bullied predicted greater increases in CRP levels, whereas bullying others predicted lower increases in CRP compared with those uninvolved in bullying.
- EPA on climate change
Though the EPA’s new report and rules on carbon emissions have evoked mixed responses, this is a bold stance for the EPA on addressing climate change.
- EPA report shows impact of changing climate on Americans’ health and environment: The report pulls together observed data on key measures of our environment, including US and global temperature and precipitation, ocean heat and ocean acidity, sea level, length of growing season, and many others. With 30 indicators that include over 80 maps and graphs showing long-term trends, the report demonstrates that climate change is already affecting our environment and our society. The report: Climate Change Indicators in the United States.
- EPA unveils sweeping rules to cut carbon emissions: The US power sector must cut carbon dioxide emissions 30 percent by 2030 from 2005 levels, according to federal regulations that form the centerpiece of the Obama administration’s climate change strategy. The proposal: Clean Power Plan Proposed Rule.
- Supreme Court ruling backs most EPA emission controls: The Environmental Protection Agency can require greenhouse-gas controls on power plants and other large stationary sources of pollution, the Supreme Court ruled, but it said the agency went too far in claiming power to regulate smaller emitters.
- Exacerbation of cigarette smoking’s effects: cumulative impacts
These studies showcase interactions of cigarette smoking with other environmental exposures.
- Does mortality risk of cigarette smoking depend on serum concentrations of persistent organic pollutants? Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study: The association between cigarette smoking and total mortality depended on serum concentration of PCBs and organochlorine pesticides.
- Lung-cancer risks sky high for smokers exposed to carcinogens: A growing body of research, including two studies under way at the University of Kentucky, shows the risk of lung cancer is much higher for smokers exposed to carcinogens such as radon, asbestos, arsenic or chromium.
- ‘Electrosmog’ disrupts orientation in migratory birds, scientists show
Scientists have demonstrated that the magnetic compass of robins fails entirely when the birds are exposed to AM radio waveband electromagnetic interference—even if the signals are just a thousandth of the limit value defined by the World Health Organization as harmless. The study: Anthropogenic electromagnetic noise disrupts magnetic compass orientation in a migratory bird. See also Cracking mystery reveals how electronics affect bird migration. This study provides clear evidence of biological impacts of very low exposures to electromagnetic fields.
- Risk factors for breast cancer
A number of new research studies this quarter highlight potential chemical and nutritional contributors to breast cancer.
- Study lists dangerous chemicals linked to breast cancer: A paper in the peer-reviewed journal Environmental Health Perspectives lists 17 chemicals to avoid and offers women advice on how to minimize their exposure. The paper: New exposure biomarkers as tools for breast cancer epidemiology, biomonitoring, and prevention: a systematic approach based on animal evidence.
- High fat diet sharply increases breast cancer risk, study finds: A high-fat diet increases the risk of the most common form of breast cancer by a fifth. Heavy consumption of saturated fat had an even bigger impact, raising the risk of hormone-sensitive breast cancer by 28 percent. The study: Dietary fat intake and development of specific breast cancer subtypes.
- Could half of all breast cancers be prevented? If girls and women of all ages adopted healthier lifestyle behaviors and the highest-risk women took preventive drugs like tamoxifen, the authors of a new report say fully half of breast cancers in the US might be avoided. The review: Priorities for the primary prevention of breast cancer.
- Solvents may raise breast cancer risk for some, study finds: Women who already have an above-average risk of breast cancer and who work with organic solvents, such as factory and laboratory workers working with benzene or other such chemicals, may have an even higher risk. The study: Breast cancer risk in association with occupational exposure to organic solvents.
- Red meat ‘linked to breast cancer’: Eating a lot of red meat in early adult life may slightly increase the risk of breast cancer. The study: Dietary protein sources in early adulthood and breast cancer incidence: prospective cohort study.
- Newborns exposed to dirt, dander, germs may have lower allergy, asthma risk
Infants exposed to rodent and pet dander, roach allergens and a wide variety of household bacteria in the first year of life appear less likely to suffer from allergies, wheezing and asthma, according to results of a recent study. Those who encounter such substances before their first birthdays seem to benefit rather than suffer from them. Importantly, the protective effects of both allergen and bacterial exposure were not seen if a child’s first encounter with these substances occurred after age 1, the research found. The study: Effects of early-life exposure to allergens and bacteria on recurrent wheeze and atopy in urban children. This research is important both because of the widespread prevalence and impact of asthma and because of the new finding of the importance of timing of exposures.
written by Arnold P. Wendroff, PhD
In response to the publication of an article and video, Dr. Wendroff submitted these comments to the publishers:
Dear Age of Autism Editors,
I was prompted to write to you by the article in today’s Age of Autism.
If in fact there was a valid correlation between mercury exposure as a cause of autism, one would expect that the Caribbean and Latino populations who are exposed to elemental mercury via its magico-religious use would experience a considerable excess of autism, which they apparently do not.
Attached are two papers (links below) describing a case of acrodynia, apparently from exposure to mercury vapor from a magico-religious mercury spill by a prior occupant of the Puerto Rican family’s apartment. Not described, but discussed in my accompanying comments were the two siblings and the mother who were also exposed, and chronically poisoned.
These exposures are relatively commonplace, as predicted by the papers by Zayas & Ozuah (1996) and Ozuah et al 2003, yet no excess cases of autism have been reported in these Caribbean and Latino populations.
If you are aware of any such correlation I would be most grateful to be informed.
Links to papers
Acrodynia and hypertension in a young girl secondary to elemental mercury toxicity acquired in the home.
Elemental mercury poisoning presenting as hypertension in a young child.
For the second quarter of 2013, we collectively selected ten topics from several dozen candidate news articles, journal articles, policy decisions and reports that have had a significant impact or are likely to have a significant impact on thinking and action in the field of environmental health. We consider these selections to be the biggest contributors toward new insights, toward changing the conversation or expanding the scope of the conversation on a topic to a new audience or awareness, or toward defining a new trend. Comments are welcome.
The selections, in no particular order:
- Chemical policy reform
A significant development in federal chemicals policy reform occurred in late May when Senator Frank Lautenberg (D-NJ) and David Vitter (R-LA) introduced a new, bipartisan bill called the Chemical Safety Improvement Act (CSIA). The introduction of the CSIA took many by surprise. Senator Lautenberg, who had been a champion for chemical policy reform for many years, passed away about a week later. CHE has compiled a selection of responses to this bill as well as links to other relevant sites for additional information: Chemical Policy Reform.
- Autism: New insights
Several new studies have provided further understanding of environmental and genetic contributors to autism spectrum disorders. We list what we view as some of the most significant of these studies:
- Autism study finds link to environment, even in womb: A new study of twins suggests that environmental factors, including conditions in the womb, may be at least as important as genes in causing autism. See the study abstract: Genetic heritability and shared environmental factors among twin pairs with autism and related studies: Quantitative trait loci for interhemispheric commissure development and social behaviors in the BTBR T+ tf/J mouse model of autism and Methylomic analysis of monozygotic twins discordant for autism spectrum disorder and related behavioural traits.
- Study links autism with antidepressant use during pregnancy. See the study abstract: Parental depression, maternal antidepressant use during pregnancy, and risk of autism spectrum disorders: population based case-control study.
- Epilepsy drug in pregnancy tied to autism risk: Women who take the epilepsy drug valproate during pregnancy are three times more likely to have a child with an autism spectrum disorder, suggests new research based on close to 700,000 babies born in Denmark. See the study abstract: Prenatal valproate exposure and risk of autism spectrum disorders and childhood autism.
- US kids born in polluted areas more likely to have autism. See the study abstract: Perinatal air pollutant exposures and autism spectrum disorder in the Children of Nurses’ Health Study II participants.
- EHN special report: ‘chemicals of high concern’ found in thousands of children’s products
An Environmental Health News analysis of thousands of reports from America’s largest companies shows that toys and other children’s products contain low levels of dozens of industrial chemicals. See the database: Children’s Safe Product Act Reports.
Ted Schettler, MD, MPH
A recent study of paternal age, de novo DNA mutations, and autism risk in Iceland, published in the journal Nature, has received considerable attention. The authors of the study found more de novo DNA mutations in children with autism and those mutations were largely traced to fathers rather than mothers. Increasing numbers of mutations were also associated with increasing paternal age. The authors wondered if recent increases in autism were largely attributable to the increasing age of fathers.
The New Yorker said, “What was surprising was how that news, which one of the study’s lead authors described as “sort of a little bit of our side story,” obscured the implications of the paper’s main findings—namely, that the genetic health of the species is now facing a serious threat.” Read more. Important as this is, most reports have failed to comment on another observation in the paper. The authors said this:
“There has been a recent transition of Icelanders from a rural agricultural to an urban industrial way of life, which engendered a rapid and sequential drop in the average age of fathers at conception from 34.9 years in 1900 to 27.9 years in 1980, followed by an equally swift climb back to 33.0 years in 2011, primarily owing to the effect of higher education and the increased use of contraception. On the basis of the fitted linear model, whereas individuals born in 1900 carried on average 73.7 de novo mutations, those born in 1980 carried on average only 59.7 such mutations (a decrease of 19.1%), and the mutational load of individuals born in 2011 has increased by 17.2% to 69.9. Demographic change of this kind and magnitude is not unique to Iceland, and it raises the question of whether the reported increase in ASD diagnosis lately is at least partially due to an increase in the average age of fathers at conception.”