A Systematic Review on Arsenic Bio-Availability in Human and Animals: Special Focus on the Rice-Human System

An evaluation of arsenic contamination status and its potential health risk assessment in villages of Nadia and North 24 Parganas, West Bengal, India

The present study was conducted to evaluate the arsenic (As) contamination and possible associated health hazards to exposed population in four villages of two districts (Nadia and North 24 Parganas) of West Bengal, India. The study included two villages each from Nadia (Jaguli and Kugacchi) and North 24 Parganas (Chamta and Byaspur) districts. Groundwater, surface water, soil, rice grains and rice-based food samples were collected from these villages. The results revealed the presence of As in high concentrations in groundwater (35.00 to 186.00 µg L-1), surface water (30.00 to 61.00 µg L-1), soil (46.17 to 66.00 mg kg-1), rice grains (0.017 to 1.27 µg g-1) and rice-based food products (0.012 to 0.40 µg g-1). The maximum As levels were recorded in all types of samples collected from Kugacchi village. The rice grain samples included high-yielding and local varieties, and the level of As in high-yielding varieties was found to be higher (0.72 to 1.27 µg g-1) than in local varieties (0.25 to 1.06 µg g-1). The data of As concentrations was used for understanding the hazard quotient (HQ) and incremental lifetime cancer risk (ILCR) to the As-exposed population, and significant non-carcinogenic and carcinogenic risks were revealed considering consumption of rice grains at 400 g per day. The study demonstrates the severity of As contamination in the surveyed villages, which may pose a hindrance to attainment of sustainable development goals (SDGs) by 2030 and proposes the implementation of requisite safety measures.

Sub-chronic low-dose arsenic in rice exposure induces gut microbiome perturbations in mice

Long-term consumption of arsenic-contaminated rice has become a public health issue that urgently needs to be addressed. In this study, mice were exposed to arsenic in rice (low dose, 0.91 mg/kg; medium dose, 9.1 mg/kg) for 30 days and 60 days, respectively, and the effects on pathological structures of spleen and skin, as well as the structure of the fecal microbiome were examined. The findings revealed dose/time cumulative effects on pathological changes, with even a low dose exposure for 30 days causing destruction of splenic follicular structure and thickening of dermal keratinized and epidermal layers. The Firmicutes/Bacteroidetes ratio in the community and the positive/negative ratio in network links were higher in arsenic groups, suggesting that arsenic resulted in a less healthy and unstable microbiome for the host. Thus lifetime consumption of arsenic in rice may have potential health effects on humans and must be carefully assessed to safeguard human health. Furthermore, in arsenic groups, arsenic-resistant bacteria or arsenic hazards remediation bacteria changed to be the dominant bacteria and acted as the core bacteria in the network modules. Some microbial arsenic transforming genes (arsC, arsR, arsA, ACR3, and aoxB) differed, indicating that the gut microbiome changed to withstand arsenic stress. Furthermore, Faecalibaculum, Lachnospiraceae_NK4A136_group, Angelakisella, Ruminiclostridium, and Desulfovibrionaceae are positively associated with arsenic dosage and may be useful in the early detection of arsenicals.

Interactions with Arsenic: Mechanisms of Toxicity and Cellular Resistance in Eukaryotic Microorganisms

Arsenic (As) is quite an abundant metalloid, with ancient origin and ubiquitous distribution, which represents a severe environmental risk and a global problem for public health. Microbial exposure to As compounds in the environment has happened since the beginning of time. Selective pressure has induced the evolution of various genetic systems conferring useful capacities in many microorganisms to detoxify and even use arsenic, as an energy source. This review summarizes the microbial impact of the As biogeochemical cycle. Moreover, the poorly known adverse effects of this element on eukaryotic microbes, as well as the As uptake and detoxification mechanisms developed by yeast and protists, are discussed. Finally, an outlook of As microbial remediation makes evident the knowledge gaps and the necessity of new approaches to mitigate this environmental challenge.