Health Risk Assessment And Preventing Strategies For Ambient Temperature Variability Exposure And Birth Defects

Background:Birth defects are one of the major global public health problems,and most of which have unknown causes.Ambient temperature variability is an important indicator to measure the unstable temperature in climate change.A large amount of evidences had shown its impact on human health,but there was a lack of epidemiological evidence on the impact on birth defects.Objectives:From the perspective of life course approach,the prevalence of birth defects was analyzed,and the impacts of exposure to ambient temperature variability on birth defects during the critical sensitive period of fetal teratogenesis(the 3rd to 8th week of gestation)were assessmented,so as to clarify the associations between exposure to ambient temperature variability and health risks of birth defects,and to identify the critical sensitive window period and susceptible population.The prevention strategies of birth defects due to exposure to ambient temperature variability were proposed accordingly.Methods:Data were collected from the Guangdong Birth Registration and Birth Defect Monitoring Database and High-resolution Air Quality Reanalysis Dataset over China.The standard deviation of daily temperature variability(TVSD)and maximum day-today temperature variability difference(TVD)were used as ambient temperature variability indices.A cross-sectional study design was used to analyze the prevalence,change trends,and spatio-temporal heterogeneity of major birth defects in Guangdong Province from 2015 to 2018.A retrospective population-based cohort study was also conducted.Guangdong Province was selected as the study area,normal and birth defects newborns and their mothers were selected as the study objects,the sensitive period of teratogenesis in utero was selected as the exposure period,ambient temperature variability as the exposure factor,and birth defects as the endpoint of health effects.Modeling was performed using a log-binomial generalized estimating equation model,and series sensitivity analysis and subgroup analysis were performed.Results:The prevalence of overall birth defects in Guangdong Province during 2015-2018 was 207.02/10,000(95%CI:205.98/10,000-208.07/10,000),showing an increasing trend(P<0.001),with significant differences among cities(P<0.001).On weekly time scales,all weekly TVSD and TVD exposure were significantly associated with increased risk of major birth defects,with RRs and corresponding 95%CI ranging from 1.03(1.01-1.05)to 1.06(1.02-1.10)with increment of 1℃(all P<0.05).For both weekly TVSD and TVD,most birth defect subgroups showed the strongest effect at 5th week of gestation.For all TVSD5,TVD5 and weekly maximum TVSD and TVD were significantly associated with all birth defects subgroups,with RR and corresponding 95%CI ranging from 1.03(1.01-1.05)to 1.19(1.08-1.31)(all P<0.05).Over time scales up to 6 weeks,TVSD3-8 and TVD3-8 were significantly associated with overall birth defects and most birth defects subgroups,with RR and corresponding 95%CI ranging from 1.12(1.01-1.25)to 1.26(1.07-1.48)(most P<0.05).The strongest associations were found for isolated defects among morphology subgroups and congenital heart defects in the site-type subgroups.The risk of birth defects was higher in non-mountain counties than in mountain counties.Conclusions:Guangdong Province is an area with a high prevalence of birth defects,with temporal variability and spatial heterogeneity.Exposure to ambient temperature variability on weekly and long-term scale was strongly associated with an increased health risk of major birth defects among 3-8 weeks of gestation.From the perspective of morphology,exposure to ambient temperature variability has the strongest effect on the risk of isolated defects.From the perspective of site-type,exposure to ambient temperature variability had the greatest effect on the risk of congenital heart defects.For overall major birth defects and most birth defects subgroups,the fifth week of gestation appears to be the most critical window for susceptibility.TVSD and TVD were similarly associated with the risk of birth defects and had the same critical sensitivity window,further strengthening the evidence.Pregnant women living in nonmountain counties appear to be more sensitive to exposure to ambient temperature variability than those living in mountainous counties.The primary prevention strategies for ambient temperature variability exposure and birth defects,including strengthening risk awareness and adaptive capacity by the public with reproductive needs in early pregnancy,strengthening health education and public health intervention by medical staffs,strengthening mechanism research and results translation by scholars,and strengthening climate governance and risk warning by the government.