Effects of PM and PM on congenital hypothyroidism in Qingdao, China, 2014–2017: a quantitative analysis

Background: We aimed to quantify the impact of PM 2.5 and PM 10 pollution on congenital hypothyroidism (CH) in Qingdao in the period 2014–2017. Methods: A generalized additive mixed model (GAMM) with time-series Poisson regression was conducted to quantify the association between PM 2.5 and PM 10 variables in the month when cases of CH were born or in the two preceding the months (lag0, lag1 and lag2) and monthly morbidity of people with CH across different populations. Results: A total of 480,633 newborns were screened for CH during 2014–2017 in Qingdao, and there were 268 cases of CH diagnosed. The count of days per month for which average concentrations of PM 2.5 and PM 10 exceed legal limits were positively associated with monthly CH morbidity at lag1 month among all the populations, and the adjusted relative risks (RRs) with exposure per 10 μg/m 3 were close among different populations. However, the number of days per month of PM 2.5 and PM 10 concentrations exceeding limits were negatively associated with CH morbidity. Additionally, the RRs of CH increase with worsening air pollution. Conclusions: Concentrations of PM 2.5 and PM 10 exceeding the legal limits are significantly associated with CH in Qingdao. Moreover, it suggests that sudden and short-term particulate matter pollution events with high levels of particulates exceeding the legal limits may be related to risk of CH.