Pollution characteristics and health risks assessment of nitrates in rural drinking water in Hainan,2012-2021
Objective To understand the nitrate pollution status in rural drinking water in Hainan Province,evaluate the health risks to the population,and provide a reference for drinking water hygiene management and intervention measures.Methods Monitoring of nitrates was conducted on 14 037 samples of rural drinking water in Hainan Province from 2012 to 2021,using the environmental health risk model from the"Technical Guidelines for Environmental Health Risk Assessment of Chemical Substances"(WS/T 777-2021)to analyze nitrate content and assess population health risks.Results A total of 14 037 water samples were tested from 2012 to 2021,with a mean nitrate concentration of 0.70 mg/L,and the nitrate compliance rate was 97.08%,and the difference between the annual compliance rates was statistically significant(χ2=97.982,P<0.001).The compliance rates during dry and wet seasons were 97.18%and 96.97%respectively,and the difference was no statistically significant(χ2=0.543,P>0.05).The compliance rates for surface water and groundwater sources were 98.95%and 95.24%respectively,and the difference was statistically significant(χ2=170.898,P<0.001).The compliance rates for finished and tap water were 96.81%and 97.26%respectively,and the difference was no statistically significant(χ2=2.319,P>0.05).The water compliance rates across various cities and counties ranged from 90.41%to 100.00%,and the difference was statistically significant(χ2=332.779,P<0.001).Over the ten years,the average non-carcinogenic risks for different age groups were all less than 1,but the maximum non-carcinogenic risks for some age groups were greater than 1.The average and maximum non-carcinogenic risks for the 1 to less than 2-year-old group were 0.052 and 4.022,respectively.Non-carcinogenic risk increased with age,peaking in the 1 to less than 2-year-old group,and then decreased with further aging.The highest values of nitrate content and maximum non-carcinogenic risks were mainly concentrated in some towns of Haikou,Baisha,Ledong,Danzhou,Lingshui,Dingan,and Changjiang.Specifically,the maximum non-carcinogenic risks of Changhua Town in Changjiang,Xincun Town in Lingshui,Zhongping Town in Qiongzhong,Haiwei Town in Changjiang were 4.022,3.656,3.148,2.998,respectively,indicating long-term exposure non-carcinogenic risk to the population.Conclusions The non-carcinogenic risk of nitrates in rural drinking water in Hainan from 2012 to 2021 is low relatively.However,regions with higher nitrate levels should undertake corresponding intervention measures,such as scaling up pipe network construction,modifying the water treatment process,and controlling pollution sources.
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