Blood lead levels of children in urban and suburban areas in China (1997-2015): Temporal and spatial variations and influencing factors.

Blood lead (Pb) poisoning is a worldwide heath problem, especially in developing countries. As the largest developing country in the world, China faces severe health challenges, in particular the threat of blood Pb poisoning. In this study, the temporal trend of Chinese children's blood lead levels (BLLs) and blood lead poisoning incidence (BLPI) (percentage of BLL>100μg/L) and its influencing factors were investigated. We collected articles on children's BLLs published from 1997 to 2017 with sampling time from 1997 to 2015 by searching the databases of VIP Medical Information System (VMIS), China National Knowledge Infrastructure (CNKI) and Wanfang Data. After a rigorous investigation, 259 articles with eligible inclusion criteria were reviewed. Meanwhile, the data of Pb concentrations in the soil of 23 cities and the annual mean PM10 (particulate matter<10μm) concentrations of 24 provincial cities were collected. The temporal trend of children's BLLs and BLPIs could be divided into three stages: upward trend from 1997 to 2000, downward trend from 2001 to 2013, and upward trend from 2014 to 2015. The decline of BLLs from 2001 was primarily due to the phasing out of leaded gasoline since 2000 in China, while the descending air quality could explain the upward trend of BLLs in the period from 2014 to 2015. The correlation and regression analysis indicated that soil and air were two major pathways of Pb exposure for children in China. Although a noticeable decrease has been shown, the Chinese children's BLLs were still significantly higher than the levels of developed countries. We highly recommended that the critical value of blood Pb poisoning should be lowered to 50μg/L in China. Guidelines on the prevention and management of blood Pb poisoning are needed in China.