Pollution characteristics, long-term variation trend, and health risk assessment of lead in ambient PM2.5 in Jinan

Abstract

BackgroundA number of studies have shown that heavy metals in atmospheric PM2.5 have impacts on human health, while studies on the impact of long-term and low-concentration exposure to lead in PM2.5 on human health are limited. ObjectiveTo investigate the pollution characteristics of lead in ambient PM2.5 and assess its chronic health risks. MethodsDaily PM2.5 concentration data in Jinan from 2014 to 2019 were collected, and the year-by-year trend of PM2.5 concentration was analyzed. Licheng District (an industrial area) and Shizhong District (a residential area) were elected to install an ambient PM2.5 monitoring stationrespectively. The sampling instrument was a 100 L·min−1 high-flow PM2.5 sampler, with a cumulative sampling time of 20-24 h per day, using a quartz fiber filter membrane for lead detection and a glass fiber filter membrane for PM2.5 determination. The sampling frequency was 7 consecutive days per month from the 10th to the 16th (A total of 493 d were sampled and some were missing; 172 d during the heating period and 321 d during the non-heating period). Two PM2.5 samples were collected in one monitoring site each day. A total of 986 samples were collected in one monitoring site. The lead content in PM2.5 samples was detected by inductively coupled plasma mass spectrometry. The concentration of PM2.5 was measured by weighing method. The annual average concentration and enrichment factor of lead in PM2.5, the change trend of lead content per unit mass of PM2.5, and the difference between heating period and non-heating period from 2014 to 2019 were estimated. Technical guide for environment health risk assessment of chemical exposure (WS/T 777-2021) was used to assess the health risks of exposure to lead in PM2.5. ResultsThe average annual concentration of lead in PM2.5 ranged from 23.2 ng·m−3 to 154.7 ng·m−3. The average concentration in heating period from 2015 to 2019 was higher than that in non-heating period, and the differences in 2015, 2017, and 2019 were statistically significant (P < 0.01 or 0.001). The enrichment factors ranged from 200 to 1342 in 2014 to 2019. The average enrichment factors in heating period in 2015, 2017, and 2018 was higher than those in non-heating period, and the difference was statistically significant (P < 0.05 or 0.001). The lead contents per unit mass of PM2.5 ranged from 493 ng·mg−1 to 1944 ng·mg−1, and the differences between heating period and non-heating period in 2014, 2017, and 2018 were statistically significant (P < 0.05 or 0.001). The average annual concentration and enrichment factor of lead in PM2.5 showed a downward trend, and thus the lead content per unit mass of PM2.5 also decreased. From 2014 to 2019, the carcinogenic risk of lead in PM2.5 in Jinan ranged from 1.69×10−8 to 2.45×10−6, showing a significant downward trend year by year, and the 95th percentile decreased by 3%-46% from the previous year. The carcinogenic risk level of lead was reduced to an acceptable level (<1×10−6) after 2017. ConclusionFrom 2015 to 2019, lead concentration and enrichment factor in PM2.5 increase during heating period compared with non-heating period, but it is not completely consistent of lead content in PM2.5 per unit mass. From 2014 to 2016, exposure to lead in PM2.5 may elevate carcinogenic risk to human. After 2017, the carcinogenic risks of exposure to lead in PM2.5 are at an acceptable level.

Keywords

• atmospheric pollution
• pm2.5
• lead
• pollution characteristics
• risk assessment