Literature Search and Selection

Keywords, such as 1) blood lead, 2) lead intoxication, 3) atmospheric lead, and 4) atmospheric heavy metals, were used to find data regarding blood lead levels in Korean population. Research Information Sharing Services, Korea Information Sharing Service, Google Scholar, and other databases were used to collect thesis, academic papers, project reports etc. with a total of 124 references initially collected from 1968 to December 2014. The papers or reports that presented results regarding occupational exposure to a high concentration of lead (n = 23), health surveys of residents living near industrial complex areas (n = 21), and articles from 1960s and 1970s that did not have clearly stated analytic methods of lead (n = 3) were all excluded. In most cases, blood lead levels were measured by the method of atomic absorption spectrophotometer, despite the fact that there were some differences in the composition of the additive (diluent) in the pretreatment process.

After ensuring that all papers utilizing the Korean National Health and Nutrition Examination Survey and the Korean National Environment Survey had no overlap, a total of 77 references, with origins spanning from 1980 to 2014, were chosen for the quantitative analysis (Figure 1). Total 49 559 individuals (12 115 men adults, 11 097 women adults, 22 507 children/adolescents, 3840 others) were included from the 77 aforementioned forms of research.

Flow chart for literature search and selection. RISS, Research Information Sharing Services; KISS, Korea Information Sharing Service.

The data of the annual average atmospheric lead concentration from 1991 to 2013 were collected from the Annual Report of Air Quality in Korea, published by the National Institute of Environmental Research (NIER). The atmospheric lead concentration was measured 5 times a month in the National Ambient Air Monitoring System (NAMIS) which started in 1991. The results were first verified by the managing institute, then sent to the NAMIS, and finally forwarded to NIER to be saved in database format.

Among preliminary studies, prior to 1991, the studies which monitored and measured atmospheric pollution over a period of at least 10 months annually were used for data prior to 1991. Any study that did not clearly state the location, method, and number of measurements was excluded. Finally, data from 1985, 1986, 1988, and 1990 were chosen for the analysis. Data from 1987 was excluded due to changes in the measurement method of atmospheric lead that caused the data to lose relevance. Because pre-1991 data were limited to Seoul, Busan, Daegu, and Gwangju, the data from 1991 to 2013 were also limited to results from these four cities, as well.