OBJECTIVEOur objective is to build a model that explains the association between the exposure to trace elements in the soil and the risk of neural tube defects.

METHODSWe built a function with different parameters to describe the effects of trace elements on neural tube defects. The association between neural tube defects and trace element levels was transformed into an optimization problem using the maximum likelihood method.

RESULTSTin, lead, nickel, iron, copper, and aluminum had typical layered effects (dosage effects) on the prevalence of neural tube defects. Arsenic, selenium, zinc, strontium, and vanadium had no effect, and molybdenum had one threshold value that affected the prevalence of birth defects.

CONCLUSIONAs an exploratory research work, our model can be used to determine the direction of the effect of the trace element content of cultivated soil on the risk of neural tube defects, which shows the clues by the dosage effect of their toxicological characteristics. Based on our findings, future biogeochemical research should focus on the direct effects of trace elements on human health.

China ; epidemiology ; Dose-Response Relationship, Drug ; Environmental Exposure ; Female ; Humans ; Metals ; chemistry ; toxicity ; Models, Biological ; Neural Tube Defects ; chemically induced ; epidemiology ; Pregnancy ; Prevalence ; Soil Pollutants ; chemistry ; toxicity ; Trace Elements ; chemistry ; toxicity

Objective: To understand the characteristics and changes of the incidence of amoebic dysentery in China during 2015-2018, explore the causes of high incidence in some areas and provide a data base for the development of national prevention and control strategies and measures. Methods: Data were collected from the infectious disease reporting management information system from Chinese Disease Control and Prevention. To understand the seasonal, population and area distributions of amoebic dysentery, descriptive epidemiological method and software SPSS 16.0 were used to analyze the amoebic dysentery data. Results: A total of 4 366 amoebic dysentery cases were reported without death in China during 2015-2018. The reported average annual incidence was 0.08/100 000, and the overall proportion of laboratory confirmed cases was 68.23%(2 979/4 366). Amoeba dysentery mainly occurred during May to October. One seasonal peak was observed in 2015 and 2017 (July and June, respectively), and two seasonal peaks were observed in 2016 and 2018 (June and October). The patients were mainly children aged under 5 years (42.28%, 1 846/4 366), and the incidence rate decreased with age in children aged under 10 years. Of these, children under 1 years of age had the highest incidence rate (1.28/100 000). The number of cumulative reported cases in Guangxi, Henan, Guangdong, Heilongjiang and Jiangxi provinces ranked top five from 2015-2018, accounting for 64.50% (2 816/4 366) of the total. The cumulative cases in Dongxing county, Guangxi, in Suixian county, Henan and in Ranghulu district, Heilongjiang, respectively accounted for more than 50.00% of the total number of cases in their provinces. Conclusions The incidence rate of amoebic dysentery reported in China during 2015-2018 showed a decreasing trend, with a higher incidence in children under 5 years old and a higher number of cases in some areas. It is suggested to further investigate and analyze the diagnosis and reporting of amoeba dysentery in key areas and promote the update of the diagnostic standards for amoeba dysentery.