Abstract
Cyanotoxins released by cyanobacteria are currently a concern due to potential impacts on plants, animals, and human health. Many instances of cyanotoxin poisoning have been reported around the world, including acute, chronic, and fatal cases. In recent years, the Tri An Reservoir (TAR) in Vietnam has experienced influxes of cyanotoxins from toxic blue-green algae at levels which exceed the World Health Organization's (WHO) permitted level of 1 μg/L. Previous studies have focused on assessing cyanobacterial diversity, the presence of cyanotoxins in water, or the effect on aquatic plants and animals. Therefore, this study aims to assess the health risks associated with cyanobacteria exposure for people living near the TAR in Dong Nai Province, Vietnam, using the Monte Carlo simulation technique. In total, 120 water samples were collected at five points of the reservoir from 2017 to 2019. Seventy-five local people who have been exposed to the water from the reservoir were interviewed. Microcystin (MC) concentration was measured with a high-pressure liquid chromatography (HPLC) system and was used to assess the health risk to local people. The results showed that the MC concentration in raw water ranged from below detection limit (BDL) to 18.67 μg/L in 2017 and from BDL to 8.6 μg/L in 2019, with the predominant variant being MC-RR. The concentration of MCs in the TAR in 2017 and 2019 exceeded the WHO's permitted level of 1 μg/L by 76% and 19%, respectively. The results showed that the rate of MC exposure likely to cause cancer was approximately 1-5%. The oral exposure rate while bathing was less than 2.5%. Direct oral exposure of cyanobacteria with no carcinogenicity was relatively high (40-50%) and the most affected group was adults.