Health risk assessment of arsenic in drinking groundwater: A case study in a central high land area of Vietnam

Arsenic contaminated groundwaters is a global environmental issue which cause serious problems for human health risks. 188 groundwater samples were collected in private wells of Lam Dong Province, a central highland area, Vietnam to investigate the health risks to the local people by using arsenic contaminated groundwater for drinking purpose. The result showed that the arsenic concentration is average of 14 μg/L and maximum of 500 μg/L. About 12% out of the total groundwater samples have arsenic concentration exceeded that value of 10 μg/L recommended for drinking water by World Health Organization (WHO, 2019). The health risk assessment showed that hazard quotient (HQ) value for adults was up to 60.6 with an average of 1.7 and about 14% of total samples show the HQ values greater than 1. The HQ value for children is average of 4.7 (maximum of 166.7) and about 23% of total groundwater samples show HQ > 1 for children. Cancer risk (CR) values were up to 27x10-4 (average of 8x10-4) for adults and 75x10-4 (average of 21x10-4) for children. About 26% and 29% of out of the total samples show CR value for adult and children greater than the CR (1×10-4) proposed by the USEPA. The result also indicated that the consumption of arsenic contaminated groundwater may seriously damage the human health. Therefore, groundwater in the area needs to be treated for arsenic removal before drinking to minimize the adverse effect on local communities’ health.

Azospira inquinata sp. nov., a nitrate-reducing bacterium of the family Rhodocyclaceae isolated from contaminated groundwater

Two novel Gram-stain-negative bacterial strains, Azo-3T and Azo-2, were isolated from a toluene-producing enrichment culture that originated from contaminated groundwater at a site in southeast Louisiana (USA). Cells are non-spore forming straight to curved rods with single polar flagella. Strains Azo-3T and Azo-2 are oxidase-positive, catalase-negative, use nitrate and nitrite as electron acceptors, and are able to fix nitrogen. Poly-β-hydroxybutyrate storage granules are produced. Dominant fatty acids when grown in R2A medium at 37 °C are C16:0, summed feature 3 (C16:1 ω7c and/or C15:0 iso 2OH), C17:0 cyclo and C18:1 ω7c. 16S rRNA gene sequence based phylogenetic analysis indicated that the strains cluster within the family Rhodocyclaceae , class Betaproteobacteria , most closely related to but distinct from type strains of the species Azospira oryzae (96.94% similarity) and Azospira restricta (95.10% similarity). Complete genome sequences determined for strains Azo-3T and Azo-2 revealed DNA G+C content of 62.70 mol%. Genome-wide comparisons based on average nucleotide identity by orthology and estimated DNA–DNA hybridization values combined with phenotypic and chemotaxonomic traits and phylogenetic analysis indicate that strains Azo-3T and Azo-2 represent a novel species within the genus Azospira for which the name Azospira inquinata sp. nov. is proposed. The type strain of Azospira inquinata is Azo-3T (=NRRL B-65590T=DSM 112046T).