Daily Archives: March 16, 2014

Factors affecting aflatoxin production in water

Al-Gabr HM, Ye C, Zhang Y, Khan S, Lin H, Zheng T. Effects of carbon, nitrogen and pH on the growth of Aspergillus parasiticus and aflatoxins production in water. J Environ Biol. 2013 Apr;34(2 Spec No):353-8.

Mycotoxins are considered as the most hazardous fungal metabolites for human, animals and plant health. Recently, more attention has been paid on the occurrence of this group of fungi in different water sources throughout the globe. In this study, Aspergillus parasiticus ATCC strain was used as representative strain producing aflatoxins in drinking water. This study aimed to investigate the activation of fungi in drinking water and their ability to produce aflatoxins (B1, B2, G1, and G2) in water under different ratios of C:N using different concentrations of total organic carbon (TOC) and total nitrogen (TN). Glucose and ammonium sulphate were used for changing the levels of TOC and TN in the selected water media. Similarly, the effects of different water pH levels from 4.5 to 8.2 on the growth of this group of fungi and aflatoxins production were also investigated. The results indicate that the growth of fungi was highest, at C:N ratio of 1:1 as compared to other selected ratios. Furthermore, the findings indicate that the pH levels 5.5-6.5 showed best growth of fungi as compared to other pH levels. Aflatoxin concentrations were measured in the water samples using HPLC technique, but selected fungi were not able to produce aflatoxins in water at applied concentrations of TOC and TN mimicking the ratios and concentrations present in the natural aquatic environment.

Water treatment with alum potash, bleaching powder and lime

Islam MS, Ansaruzzaman M, Mahmud ZH, Matin MA, Islam MS, Mallik AK, Neogi SB, Jahid IK, Endtz HP, Cravioto A, Sack DA.  A novel and simple mixture as point-of-use water treatment agent to produce safe drinking water. Trans R Soc Trop Med Hyg. 2014 Mar 11.

BACKGROUND: People in rural Bangladesh have a poor understanding of the link between use of contaminated surface water and disease. An inexpensive point-of-use water treatment agent was developed to purify surface water.

METHODS: Surface water was collected from various sources in Bangladesh from February 2007 to January 2008. Microbiological and physicochemical parameters of raw and treated surface water were analysed. Water was treated with a mixture of alum potash, bleaching powder and lime, or with each agent individually.

RESULTS: Raw water was contaminated with bacteria, the counts for total coliforms, faecal coliforms and faecal streptococci being 26 431, 14 548 and 240 colony-forming units (cfu) 100 ml-1, respectively. These counts fell to 0 cfu 100 ml-1 after treatment with the mixture. The count of artificially introduced Vibrio cholerae was also reduced to 0 cfu 100 ml-1 after treatment. Treatment of raw water altered the pH from 6.90 to 6.87, turbidity from 21.61 to 3.55 nephelometric turbidity units (NTU), residual chlorine from 0 to 0.09 mg litre-1, conductivity from 124.03 to 229.96 µS cm-1, and total dissolved solids from 59.40 to 199.25 mg litre-1. All these results of treatment were within the range recommended by the WHO as acceptable for drinking water.

CONCLUSION: The mixture of alum potash, bleaching powder and lime described can be safely used to disinfect contaminated surface water to make it suitable for drinking and other household purposes in Bangladesh.

Click here for full paper (fee).

How the global warming scare began – John Coleman

Except for the silly comments at the beginning about the earth being 4 billion years old, it is an insightful review of the history of the global warming scare.

Safety threshold of drinking water fluoride estimated at 0.8 mg/L for China

Pan S, An W, Li H, Yang M. [Using fractional polynomials to estimate the safety threshold of fluoride in drinking water]. Wei Sheng Yan Jiu. 2014 Jan;43(1):27-31. [Article in Chinese]

OBJECTIVE: To study the dose-response relationship between fluoride content in drinking water and prevalence of dental fluorosis on the national scale, then to determine the safety threshold of fluoride in drinking water.

METHODS: Meta-regression analysis was applied to the 2001-2002 national endemic fluorosis survey data of key wards. First, fractional polynomial (FP) was adopted to establish fixed effect model, determining the best FP structure, after that restricted maximum likelihood (REML) was adopted to estimate between-study variance, then the best random effect model was established.

RESULTS: The best FP structure was first-order logarithmic transformation. Based on the best random effect model, the benchmark dose (BMD) of fluoride in drinking water and its lower limit (BMDL) was calculated as 0.98 mg/L and 0.78 mg/L. Fluoride in drinking water can only explain 35.8% of the variability of the prevalence, among other influencing factors, ward type was a significant factor, while temperature condition and altitude were not.

CONCLUSION: Fractional polynomial-based meta-regression method is simple, practical and can provide good fitting effect, based on it, the safety threshold of fluoride in drinking water of our country is determined as 0.8 mg/L.