In 2005, NHS II participants were asked whether any of their children had been diagnosed with autism, Asperger’s syndrome, or “other autism spectrum,” and 839 women replied affirmatively. In 2007, we initiated a pilot follow-up study, shortly followed by a full-scale follow-up as described previously (). The follow-up questionnaire included questions about the pregnancy and birth, child’s sex, and diagnosis. NHS II protocol allows re-contacting only the nurses who responded to the most recent biennial questionnaire. Thus, this follow-up was attempted with the 756 mothers of ASD cases for whom this was the case. Mothers who reported having more than one child with ASD were directed to report about the youngest one. Controls were selected from among parous women not reporting a child with ASD in 2005. For each case mother, controls were randomly selected from among those women who gave birth to a child in a matching birth year, to yield a total of 3,000 controls. Six hundred thirty-six (84%) mothers of cases and 2,747 (92%) mothers of controls responded; 164 women (including 51 case mothers) declined to participate.
Participants. The study population included offspring of participants in NHS II, a prospective cohort of 116,430 U.S. female nurses 25–43 years of age when recruited in 1989, followed biennially (). NHS II participants originally were recruited from 14 states in all regions of the continental United States, but they now reside in all 50 states. The study was approved by the Partners Health Care Institutional Review Board and complied with all applicable U.S. regulations; return of completed questionnaires constituted consent to participate.
Four scenarios of shale gas extraction were modeled for our study site using the LUISA modeling platform. The main variables taken into account in the scenario definitions were the technology used, land and water requirements, and the legislation which may be put in place. Several scenarios were used to allow assessment of the range of possible impacts on the freshwater resources available.
Whether or not a registrant’s fitness to practise is impaired is a question for the panel alone, after consideration of all the circumstances of the case. In reaching its determination, the panel paid regard to the public interest in the wide sense (ie the protection of service users, the maintenance of public interest in the profession and the regulatory process and the upholding of proper standards of conduct and behaviour). The panel also took into account the potential risk to service user safety if an occupational therapist in the registrant’s position was working with service users when certified unfit to work.
The panel was of the view that the registrant’s misconduct was very serious. It reflected seven separate acts of dishonesty committed over two months where the objective was personal financial gain. The panel accepted the registrant had admitted her dishonesty from the outset and had shown genuine remorse. However, in all the circumstances of the case, the panel found her fitness to practise is currently impaired.
In the case of Poland, the use of groundwater resources up to 1–2 km deep is permitted (Uliasz-Misiak et al. ). Since we lack data on the potential source of water for use in fracking, we assume the same shares as for industrial purposes per catchment. This means that on average for our study area we assume 28 % of the water for fracking to be withdrawn from groundwater resources, and the remaining 72 % from surface water bodies. Since the assumed lifespan of the well pads is 10 years, we divide their water use over two of the 5-year time steps. We assume the water use to be proportional to the gas production, so divide the share of water use according to the production curve presented in Broderick et al. (). Seventy percent of the total water use per well pad is therefore allocated in the first time step, and thirty percent in the following time step. This amount was then divided by 5 to estimate the actual amount of water required for 1 year to ensure comparability with the competing water uses (which are calculated annually).
Upon completion of the fracking process, the direction of fluid flow reverses, with a proportion of the injected fluid returning to the surface. This “flowback” usually ranges from 5 to 50 % of injected freshwater (Sumi ; NYSDEC ; DGIP ), and in some cases may even reach up to 70 % (King ). Flowback water may also potentially be recycled, hence reducing cumulative freshwater demands. Gaudlip and Paugh () suggest a recycling rate for flowback water of 70 % in Pennsylvania for best-performing companies, and up to 71.5 % was measured for the Marcellus shale in 2011 (Maloney and Yoxtheimer ). This said, on average in the US only some 6–10 % of total water used in fracking is recovered and re-used on-site (Mantell ). For the high impact scenario, we therefore assume there to be no recovered or recycled flowback water. In the low impact scenario, we assume a maximum flowback of 70 %, of which 70 % is recycled on-site, so reducing the total amount of water consumed by 49 %.
In our nested case–control study of nurses from across the continental United States, ambient PM2.5 concentrations during pregnancy were significantly associated with having a child diagnosed with ASD. Importantly, the association we found appeared specific to PM2.5 during pregnancy; PM2.5 exposure before or after pregnancy showed weaker associations with ASD, and PM10–2.5 during pregnancy showed little association with ASD. In a model mutually adjusted for all three exposure periods, only the pregnancy period was associated with ASD. The change in the ORs with mutual adjustment did not appear to be an artifact of collinearity because the precision of the mutually adjusted model was not substantially lower than the single exposure model (e.g., CI widths for an IQR change in PM2.5 during pregnancy of 2.3 vs. 1.7, respectively). The 95% CIs were not notably larger in this analysis, suggesting that collinearity was not a significant problem. Moreover, during pregnancy we found the association to be specifically with the third-trimester exposure in models that included exposure in all trimesters together. The specificity of the association to the prenatal period is in line with several other lines of evidence that suggest a prenatal origin of ASD, including data on differences in brain cytoarchitecture in brains of children with ASD (; ) and associations between maternal exposure to teratogens during pregnancy and ASD (). Our results also suggest an association predominantly in boys, but this finding should be interpreted with caution, given the small number of girls with ASD in our sample.
ASD cases were more likely to be male, to have been exposed to maternal preeclampsia or maternal smoking during gestation, and to be missing data on premature birth compared with controls (). The median (25th–75th percentile) year of birth for cases and controls was the same: 1993 (1991–1996). As expected given time trends in air pollution, control children born in earlier years were more likely to be in higher PM2.5 quartiles. Census income and parental age also decreased slightly, but generally steadily by exposure, whereas there was little clear pattern of difference by exposure for other variables ().
These results generally agree with previous studies. A report from the CHildhood Autism Risks from Genetics and the Environment (CHARGE) study among 304 ASD cases and 259 controls, in several areas in California, used residential address history reported by parents to calculate distance to roads as a proxy for traffic-related air pollution exposure and found increased risk for ASD among women who lived in proximity to a freeway (). Further analysis of the CHARGE study group in a subset of 279 cases and 245 controls using data from the U.S. EPA Air Quality System suggested positive associations of ASD with traffic-related air pollution during pregnancy, and specifically with PM2.5 (). ASD was also associated with pregnancy exposure to PM10, and—in contrast to our results—the association with traffic-related air pollution exposure during the first year of life was higher than that found for the exposure during pregnancy. In the CHARGE study, associations were also seen with exposures in the year after birth that were about as strong as exposures during pregnancy. Our findings suggested a weaker association with postpregnancy exposure that was essentially null in models that included exposure during all time periods. In the CHARGE study, however, the pregnancy and postpregnancy exposure periods were not included together in the same regression model.