Spatial and Temporal Distribution of Arsenic Concentration in Rural Drinking Water and Health Risk Assessment in Northern China over the past 10 years: A Case Study of Inner Mongolia Autonomous Region

Abstract Background To monitor the arsenic content in drinking water in rural areas of Inner Mongolia Autonomous Region from 2013 to 2022 and assess its carcinogenic and non-carcinogenic risks, in order to provide guidance for optimizing rural water supply projects and to provide a basis for further promoting population health strategies. Methods Water samples from rural areas of Inner Mongolia Autonomous Region were collected during the dry season (May) and the wet season (August-September) each year from 2013 to 2022, with a total of 42,695 samples collected over the 10-year period. The arsenic content in the drinking water was tested following the "Inspection Methods for Drinking Water Standards - Metal Index" (GB/T5750.6-2006). The environmental health risk assessment was conducted using the health risk assessment model recommended by the United States Environmental Protection Agency (USEPA). The Mann-Whitney U test was used to compare the arsenic concentrations in drinking water from different water sources. Results Overall, the arsenic concentrations in drinking water in the western and central regions of Inner Mongolia Autonomous Region were higher than those in the eastern region. The arsenic concentration in rural drinking water showed a significant decreasing trend from 2013 to 2022, with over 98% of water samples qualified for arsenic standards by 2022. From 2013 to 2019, the arsenic concentration in drinking water from groundwater sources was higher than that from surface water sources (P <0.05), while there was no difference between the concentrations from different water sources from 2020 to 2022. The non-carcinogenic oral exposure risk (P95) of arsenic in drinking water for adults was higher than 1 from 2013 to 2018, and for children, it was higher than 1 from 2013 to 2015. The average, median, and P95 of the carcinogenic oral exposure risk of arsenic ingestion in drinking water from 2013 to 2022 were all higher than 1×10 -6 for the entire population. Sensitivity analysis showed that the contribution of drinking water arsenic concentration to the health risk was the largest for both adults and children, and the weight of the entire population had a negative contribution to the risk values. Conclusion Over the 10-year period, the situation of arsenic exceeding the standard in rural drinking water in Inner Mongolia Autonomous Region has improved, with the overall exceeding rate reduced and the health risks to the population decreased. However, there still exists a certain carcinogenic risk, so targeted measures should be further taken to continue promoting the improvement of water quality in rural areas.