Maternal exposure to PM2.5 may increase the risk of congenital hypothyroidism in the offspring: a national data-based study in China

Exposure assignment. The present study collected the monthly average levels of PM2.5, PM10 and AQI for 367 major cities in China from the 1st of January 2014 to the 30th of December 2015. These 367 cities were representative of the major prefecture-level cities of the 30 Chinese provinces (with the exception of Tibet, Taiwan, Hong Kong and Macau). In the present study, ambient air pollution exposure data were provided by the Chinese Air Quality Online Monitoring and Analysis Platform, which collected and released real-time and historical data on PM2.5, PM10 and AQI exposure levels (Chinese 2018). The data of this website originated mainly by the real-time data of ambient air monitoring that were recorded by the Ministry of Ecology and Environment of the People’s Republic of China. Each pollutant was continuously measured. PM2.5 was measured by β ray and Tapered Element Oscillating Microbalance, and PM10 was measured by light scattering methods. CH newborn screening. The annual incidence of CH in the 30 provinces in China from the 1st of October 2014 to the 30th of September 2015 was analyzed in the present study. The data were derived from the annals on the Chinese neonatal metabolic disease screening in 2015. It was compiled by the National Office of the Maternal and Child Health Surveillance (NOMCHS), based on the Chinese Newborn Screening information System (CNSIS), and published in the Chinese Maternal and Child Health Surveillance Network in February 2017(Yi Mou 2017). CNSIS is a screening program for newborns performed across the country, including the screening of CH. Whole-blood was collected from every newborn on filter papers for the measurement of the serum levels of thyrotropin (TSH) between 72 h and 7 days following birth. Premature, low birth weight or sick neonates and those who were discharged early within 7 days of birth were sampled within 20 days after birth. Any cases that indicated elevated TSH levels (higher than 10 to 20 μIU/ml) through double testing were followed-up and subjected to further diagnosis. Finally, the diagnosis of CH was confirmed by trained pediatric endocrinologists based on serum thyroid function tests (increased serum TSH, and reduced serum free thyroxine (FT4)). Each newborn diagnosed with CH was reported to local newborn screening centers (LNBSCs). Subsequently, a provincial newborn screening center (PNBSC) was established to guide and supervise the LNBSCs for all neonatal screening practices. The screening resul