The goal of this study is to reframe the analysis and discussion of extreme heat projections to improve communication of future extreme heat risks in the United States. We combine existing data from 31 of the Coupled Model Intercomparison Project Phase 5 models to examine future exposure to extreme heat for global average temperatures of 1.5, 2, 3, and 4 °C above a preindustrial baseline. We find that throughout the United States, historically rare extreme heat events become increasingly common in the future as global temperatures rise and that the depiction of exposure depends in large part on whether extreme heat is defined by absolute or relative metrics. For example, for a 4 °C global temperature rise, parts of the country may never see summertime temperatures in excess of 100 °F, but virtually all of the country is projected to experience more than 4 weeks per summer with temperatures exceeding their historical summertime maximum. All of the extreme temperature metrics we explored become more severe with increasing global average temperatures. However, a moderate climate scenario delays the impacts projected for a 3 °C world by almost a generation relative to the higher scenario and prevents the most extreme impacts projected for a 4 °C world.
Background: Setting health-protective standards for poly- and perfluoroalkyl substances (PFAS) exposure requires estimates of their population toxicokinetics, but existing studies have reported widely varying PFAS half-lives (T ½ ) and volumes of distribution (V d ). Objectives: We combined data from multiple studies to develop harmonized estimates of T ½ and V d , along with their interindividual variability, for four PFAS commonly found in drinking water: perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), perfluorononanoic acid (PFNA), and perfluorohexane sulfonate (PFHxS). Methods: We identified published data on PFAS concentrations in human serum with corresponding drinking water measurements, separated into training and testing data sets. We fit training data sets to a one-compartment model incorporating interindividual variability, time-dependent drinking water concentrations, and background exposures. Use of a hierarchical Bayesian approach allowed us to incorporate informative priors at the population level, as well as at the study level. We compared posterior predictions to testing data sets to evaluate model performance. Results: Posterior median (95% CI) estimates of T ½ (in years) for the population geometric mean were 3.14 (2.69, 3.73) for PFOA, 3.36 (2.52, 4.42) for PFOS, 2.35 (1.65, 3.16) for PFNA, and 8.30 (5.38, 13.5) for PFHxS, all of which were within the range of previously published values. The extensive individual-level data for PFOA allowed accurate estimation of population variability, with a population geometric standard deviation of 1.57 (95% CI: 1.42, 1.73); data from other PFAS were also consistent with this degree of population variability. V d estimates ranged from 0.19 to across the four PFAS, which tended to be slightly higher than previously published estimates. Discussion: These results have direct application in both risk assessment (quantitative interspecies extrapolation and uncertainty factors for interindividual variability) and risk communication (interpretation of monitoring data). In addition, this study provides a rigorous methodology for further refinement with additional data, as well as application to other PFAS. https://doi.org/10.1289/EHP10103
BackgroundThe World Health Organization recommends influenza vaccination for pregnant women. However, few data exist on influenza incidence and clinical course among pregnant women in middle-income countries where influenza vaccine use during pregnancy is often limited. We conducted a prospective cohort study of pregnant women to estimate incidences of influenza in Lima, Peru; Bangkok, Thailand; and Nagpur, India.MethodsPrior to and early in the 2017 and 2018 influenza seasons, we enrolled pregnant women aged > 18 years with expected delivery dates > 8 weeks after the start of the season. We contacted women twice weekly until end of pregnancy to identify illnesses with myalgia, cough, runny nose, sore throat, or difficulty breathing and collected nasal swabs from symptomatic women for influenza real-time reverse transcription polymerase chain reaction testing. Using 2017 cohort data, we calculated crude incidences per 10,000 pregnancy-months during influenza season by site and trimester and overall incidence weighted for population of women of childbearing age in each country.ResultsWe enrolled 4774 women with a median age of 26 years (interquartile range [IQR] 23–31) and gestational age of 20 weeks (IQR 15–24); 15% received influenza vaccine. Local influenza seasons spanned 4.5–8 months. Overall, 143 participants (3%) had influenza (113 (79%) influenza A and 30 (21%) influenza B). Weighted influenza incidence was 88.7/10,000 pregnancy-months (95% CI 68.6–114.8), though incidences varied up to two-fold by site (Figure 1). Incidences did not differ by pregnancy trimester (Figure 2). Among the 143 influenza episodes, the median duration was 7 days (IQR 5–10), 30% involved fever or chills, 43% disrupted daily activities, 47% prompted medical attention, 4% were associated with hospitalization, and < 1% were treated with antiviral medications.ConclusionOverall, pregnant women had an average risk of influenza of 0.9% per month of pregnancy spent in the influenza season with almost half of illnesses disrupting daily activities and prompting medical attention. Influenza-associated hospitalization was infrequent. These findings provide valuable inputs to estimate illnesses averted by vaccine programs and evaluate their cost–benefit among pregnant women in middle-income countries. Disclosures All authors: No reported disclosures.
Background The World Health Organization (WHO) recommends case definitions for influenza surveillance that are also used in public health research, though their performance has not been assessed in many risk groups, including pregnant women in whom influenza may manifest differently. We evaluated the performance of symptom-based definitions to detect influenza in a cohort of pregnant women in India, Peru, and Thailand. Methods In 2017 and 2018, we contacted 11,277 pregnant women twice weekly during the influenza season to identify illnesses with new or worsened cough, runny nose, sore throat, difficulty breathing or myalgia, and collected data on other symptoms and nasal swabs for influenza rRT-PCR testing. We calculated sensitivity, specificity, positive predictive value and negative predictive value of each symptom-predictor, WHO respiratory illness case definitions and a de novo definition derived from results of multivariable modelling. Results Of 5,444 eligible illness episodes among 3,965 participants, 310 (6%) were positive for influenza. In a multivariable model, measured fever ≥38° Celsius (adjusted odds ratio = 4.6, 95% confidence interval [CI] = 3.1, 6.8), myalgia (3.0, 95% CI: 2.2, 4.0), cough (2.7, 95% CI: 1.9, 3.9), and chills (1.6, 95% CI: 1.1, 2.4) were independently associated with influenza illness. A definition based on these four (measured fever, cough, chills or myalgia), was 95% sensitive and 27% specific. The WHO influenza-like illness (ILI) definition was 16% sensitive and 98% specific. Conclusions The current WHO ILI case definition was highly specific but had low sensitivity. The intended use of case definitions should be considered when evaluating the tradeoff between sensitivity and specificity.
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