The additivity of multiple doses of a liver carcinogen in rats

The temporal pattern and dose-rate dependence of liver cancer in rats fed 2-fluorenylacetamide (2-FAA) was compared to analytical formulas derived from a specific model. The model was based on the idea that carcinogens have two distinct actions on cells: (1) transformation and (2) acceleration of progression. Transformed cells are by definition progressing toward cancer, but their rate of progression may depend on several factors, specifically, the amount of carcinogen. In the experiments the carcinogen was removed from the diet after various times and the rate of tumor progression was estimated from the time of tumor occurrence. The results were consistent with the idea that 2-FAA accelerated the progression of the cancers. The model provides a simple explanation of Druckrey's law in that the temporal occurrence of tumors induced by a carcinogen represents the acceleration of a naturally occurring disease progression.     

Arsenic contamination in the Kanker district of central-east India: geology and health effects

This paper identifies newer areas of arsenic contamination in the District Kanker, which adjoins the District Rajnandgaon where high contamination has been reported earlier. A correlation with the mobile phase episodes of arsenic contamination has been identified, which further hinges on the complex geology of the area. Arsenic concentrations in both surface and groundwater, aquatic organisms (snail and water weeds) soil and vegetation of Kanker district and its adjoining area have been reported here. The region has been found to contain an elevated level of arsenic. All segments of the ecoysystem are contaminated with arsenic at varying degrees. The levels of arsenic vary constantly depending on the season and location. An analysis of groundwater from 89 locations in the Kanker district has shown high values of arsenic, iron and manganese (mean: 144, 914 and 371 μg L⁻¹, respectively). The surface water of the region shows elevated levels of arsenic, which is influenced by the geological mineralised zonation. The most prevalent species in the groundwater is As(III), whereas the surface water of the rivers shows a significant contamination with the As(V) species. The analysis shows a bio-concentration of the toxic metals arsenic, nickel, copper and chromium. Higher arsenic concentrations (groundwater concentrations greater than 50 μg L⁻¹) are associated with sedimentary deposits derived from volcanic rocks, hence mineral leaching appears to be the source of arsenic contamination. Higher levels of arsenic and manganese in the Kanker district have been found to cause impacts on the flora and fauna. A case study of episodic arsenical diarrhoea is presented.     

Butachlor degradation in tropical soils: effect of application rate, biotic-abiotic interactions and soil conditions

The degradative characteristics of butachlor (N-Butoxymethyl-2-chloro-2',6'-diethyla- cetanilide) were studied under controlled laboratory conditions in clay loam alluvial (AL) soil (Typic udifluvent) and coastal saline (CS) soil (Typic endoaquept) from rice cultivated fields. The application rates included field rate (FR), 2-times FR (2FR) and 10-times FR (10FR). The incubation study was carried out at 30 degrees C with and without decomposed cow manure (DCM) at 60% of maximum water holding capacity (WHC) and waterlogged soil condition. The half-life values depended on the soil types and initial concentrations of butachlor. Butachlor degraded faster in AL soil and in soil amended with DCM under waterlogged condition. Microbial degradation is the major avenue of butachlor degradation from soils.     

Effect of pencycuron on microbial parameters of waterlogged soil

A laboratory study was conducted to monitor the effect of pencycuron [1-(4-chlorobenzyl)-1-cyclopentyl-3-phenylurea] on microbial parameters of alluvial (AL) soil (Typic udifluvent) and coastal saline (CS) soil (Typic endoaquept) under waterlogged condition. Pencycuron at field rate (FR), 2FR and 10FR affected the microbial biomass C (MBC), soil ergosterol content and fluorescein diacetate hydrolyzing activity (FDHA) differentially. The DCM amendment did not seem to have any counteractive effect on the toxicity of pencycuron on the microbial variables. The change in microbial metabolic quotient (qCO2) and microbial respiration quotient (QR), indicated pencycuron induced disturbance at 10FR. Present study revealed that the metabolically activated microbial population was more suppressed compared to the dormant population.     

Fluoride contamination in and around selected geothermal sites in Odisha,Eastern India: assessment of ionic relations,fluoride exposure and remediation

Environmental Science and Pollution Research - Fluoride contamination in groundwater is a major problem throughout the world as well as in India. High-fluoride content was reported in the hot...