Ecological and human health risk assessments of cyanotoxins and heavy metals in a drinking water supply reservoir.

Human beings are frequently exposed to a mixture of chemical pollutants through the ingestion of contaminated drinking water. The present study aimed to assess the ecological and human health risks associated with the contamination of cyanotoxins and heavy metals in a drinking water supply reservoir, the Tri An Reservoir (TAR), in Vietnam. Results demonstrated that the concentrations of individual heavy metals varied in the following order: iron (Fe) > lead (Pb) > arsenic (As) > zinc (Zn). Although the ecological potential risk of heavy metals was low during the study period, the concentration of Fe sometimes exceeded the Vietnamese standard for drinking water. Toxic cyanobacteria and microcystins (MCs) frequently occurred in the TAR with the highest density of 198.7 × 103 cells/mL and 7.8 µg/L, respectively, indicating a high risk of health impacts to humans. The results of the study indicate that exposure to heavy metals does not pose any non-carcinogenic health risks for both adults and children. However, the contamination of MCs in the surface water posed a serious disease enhancement to both adults and children through direct ingestion and dermal absorption.

Health risk assessment related to cyanotoxins exposure of a community living near Tri An Reservoir, Vietnam.

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.