No abstract

The levels of some heavy metals in spent engine oils and in the fingernails of auto-mechanics were studied. Engine oils and fingernails were collected from auto-mechanics who had practiced between ≤ 5 years, ≤ 10 years and ≤ 15 years in 3 auto-mechanic workshop clusters. Pb, Ni, V, Cd, and As levels were determined using Atomic Absorption Spectrophotometer. The mean levels of Pb, Ni, V and Cd in spent engine oils were 14.31, 2.25, 0.38 and 2.07 ppm respectively, and these far exceeded their permissible exposure limits. The mean levels of heavy metals in the fingernails of auto-mechanics who had practiced for ≤ 5 years, ≤ 10 years and ≤ 15 years were all considerably below their pathological thresholds. Thus, auto-mechanics in the study area are exposed to unsafe levels of Pb, Ni, V, and Cd, but no immediate threat of their toxicities in the study population exist. However, a progressive bioaccumulation of the heavy metals was observed with increase in years of practice.

Sediment-dwelling biota such as mollusks (clam) and crabs collected from mangrove areas of the Calabar River are important routes of exposure to organochlorine pesticides (OCPs) contamination. Residual levels of OCPs including HCHs, DDTs, heptachlor, heptachlor epoxide, aldrin, endrin ketone, entrin aldehyde, dieldrin, endosulfan, endosulfan sulphate, methoxychlor, were determined in these organisms. The results revealed the OCP loads to be predominated by DDTs and HCHs (much of which was derived from illegal usage of GAMMALIN 20 for fishing) with the overall means of 49.6 and 35.1 ng/g wet weight (ww), respectively, at 100% frequencies of occurrence. Concentrations of other OCP components were generally low and were not detected in all biota samples. This probably reflects low utilization of these OCPs in the region and/or low bioaccumulation potential in the biota species. In general, the OCP concentrations were higher in freshwater mollusks and crabs than in brackish water, indicating that freshwater biota were more easily influenced by OCPs than their brackish water counterparts. One way analysis of variance (ANOVA) indicated no significant relationship between lipid content (LC) or body size of organisms and contaminant load, probably because of the non-equilibrium situation: smaller animals accumulated more OCPs than their larger counterparts, suggesting different uptake and elimination rates for these compounds. Biota-sediment accumulation factors (BSAFs) for DDTs and HCHs varied among the organisms and were in the ranges 1.02-9.78 and 0.74-8.72, respectively, indicating probably that HCHs were less bio-available in the river than DDTs. They were generally lower for highly polluted site (UMA; freshwater area) and higher for areas of low anthropogenic pressure (MR-brackish water area). Risk assessment matched against various standards clearly showed that the biota were highly contaminated with HCHs and DDTs, and may pose serious health threats to local inhabitants of the catchments. Furthermore, other selected OCPs such as heptachlor and dieldrin may in addition pose lifetime cancer risk, especially to residents of the riverine/coastal communities who often consume more of these organisms than those living inland.

The effect in rabbits of the sarinase levels of liver and plasma, and of cholinesterase levels of plasma on survival after repeated intraperitoneal or subcutaneous doses of sarin has been investigated. When the intraperitoneal route was used a significant correlation was found between liver sarinase and survival. Survival after subcutaneous injection was not affected by the liver sarinase. No correlation was found between plasma sarinase or plasma cholinesterase and survival for either the intraperitoneally or subcutaneously injected rabbits.

The cells of the liver and kidneys from three species known to be comparatively susceptible to sarin (rabbit, guinea pig, and monkey) and two species known to be less susceptible (rat and mouse) have been fractionated into their cell constituents (nuclei, mitochondria, microsomes, and non-particulate fraction). Each fraction has been tested for sarinase activity. The non-particulate fraction had the highest activity, the microsomes the second highest, the mitochondria the third highest, and the nuclei the lowest. The significance of the differences found in the distribution of sarinase activity in the cell fractions is discussed.Monkey cell fractions were also tested with ethyl N,N-dimethylphosphoramidocyanidate (tabun) as the substrate. The results were similar to those obtained with sarin, suggesting that the same enzyme was responsible for the hydrolysis of both substrates.