Daily Archives: January 18, 2015

Salinity, Palatability, and Cholera in Coastal Bengladesh

Grant SL, Tamason CC, Hoque BA, Jensen PK. Drinking Cholera: Salinity Levels and Palatability of Drinking Water in Coastal Bangladesh. Tropical Medicine and International Health 2015 Jan 8. doi: 10.1111/tmi.12455.

OBJECTIVES: To measure the salinity levels of common water sources in coastal Bangladesh and explore perceptions of water palatability among the local population in order to investigate the plausibility of linking cholera outbreaks in Bangladesh with ingestion of saline-rich cholera infected river water.

METHODS: 100 participants took part in a taste-testing experiment of water with varying levels of salinity. Salinity measurements were taken of both drinking and non-drinking water sources. Informal group discussions were conducted to gain an in-depth understanding of water sources and water uses.

RESULTS: Salinity levels of non-drinking water sources suggest that the conditions for V. cholerae survival exist 7-8 days within the local aquatic environment. However, 96% of participants in the taste testing experiment reported that they would never drink water with salinity levels that would be conducive to V. cholerae survival. Furthermore, salinity levels of participant’s drinking water sources were all well below the levels required for optimal survival of V. cholerae. Respondents explained that they preferred less salty and more aesthetically pleasing drinking water.

CONCLUSION: Theoretically, V. cholerae can survive in the river systems in Bangladesh; however, water sources which have been contaminated with river water are avoided as potential drinking water sources. Furthermore, there are no physical connecting points between the river system and drinking water sources among the study population, indicating that the primary driver for cholera cases in Bangladesh is likely not through the contamination of saline-rich river water into drinking water sources.

Click here for paper (fee).

Ocean Calamities Oversold

Alarming claims and the push for legislation/regulation and government funding go hand-in-hand.

Carlos M. Duarte, Robinson W. Fulweiler, Catherine E. Lovelock, Paulina Martinetto, Megan I. Saunders, John M. Pandolfi, Stefan Gelcich, Scott W. Nixon. Reconsidering Ocean Calamities BioScience (2014) doi: 10.1093/biosci/biu198

The proliferation of a number of pressures affecting the ocean is leading to a growing concern that the state of the ocean is compromised, which is driving society into pessimism. Ocean calamities are disruptive changes to ocean ecosystems that have profound impacts and that are widespread or global in scope. However, scrutiny of ocean calamities to ensure that they can be confidently attributed to human drivers, operate at widespread or global scales, and cause severe disruptions of marine social-ecosystems shows that some of the problems fail to meet these requirements or that the evidence is equivocal. A number of biases internal and external to the scientific community contribute to perpetuating the perception of ocean calamities in the absence of robust evidence. An organized auditing of ocean calamities may deliver a more precise diagnosis of the status of the oceans, which may help to identify the most pressing problems that need be addressed to conserve a healthy ocean.

Click here for paper (Open Access).

Drinking Water Arsenic Exposure in the Mekong Delta

Merola RB, Hien TT, Quyen DT, Vengosh A. Arsenic exposure to drinking water in the Mekong Delta. The Science of the Total Environment. 2015 Jan 9;511C:544-552. doi: 10.1016/j.scitotenv.2014.12.091.

Arsenic (As) contamination of groundwater drinking sources was investigated in the Mekong Delta, Vietnam in order to assess the occurrence of As in the groundwater, and the magnitude of As exposure of local residents through measurements of As in toenails of residents consuming groundwater as their major drinking water source. Groundwater (n=68) and toenail (n=62) samples were collected in Dong Thap Province, adjacent to the Mekong River, in southern Vietnam. Fifty-three percent (n=36) of the wells tested had As content above the World Health Organization’s (WHO) recommended limit of 10ppb. Samples were divided into Northern (mean As=4.0ppb) and Southern (329.0ppb) groups; wells from the Southern group were located closer to the Mekong River. Elevated As contents were associated with depth (<200m), salinity (low salinity), and redox state (reducing conditions) of the study groundwater. In 79% of the wells, As was primarily composed of the reduced As(III) species. Arsenic content in nails collected from local residents was significantly correlated to As in drinking water (r=0.49, p<0.001), and the relationship improved for pairs in which As in drinking water was higher than 1ppb (r=0.56, p<0.001). Survey data show that the ratio of As in nail to As in water varied among residents, reflecting differential As bioaccumulation in specific exposed sub-populations. The data show that water filtration and diet, particularly increased consumption of animal protein and dairy, and reduced consumption of seafood, were associated with lower ratios of As in nail to As in water and thus could play important roles in mitigating As exposure in areas where As-rich groundwater is the primary drinking water source.

Click here for paper (fee).