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D R Chettle

Publications and source records attributed to D R Chettle.

92 records · Page 6Linked to original sources
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In vivo measurements of lead in bone in long-term exposed lead smelter workers.

In-vivo measurements of lead concentrations in calcaneus (mainly trabecular bone) and tibia (mainly cortical bone) were performed by x-ray fluorescence (XRF) in 70 active and 30 retired lead smelter workers who had long-term exposure to lead. Comparison was made with 31 active and 10 retired truck assembly workers who had no known occupational exposure to lead. After physical examination, all participants provided blood and urine samples and answered a computerized questionnaire. Since 1950, blood lead has been determined repeatedly in lead workers at the smelter, which made it possible to calculate a time-integrated blood lead index for each worker. Lead concentrations in blood, urine, calcaneus, and tibia in active and retired lead workers were significantly higher than in the corresponding control groups (p < .001). The highest bone lead concentrations were found among retired lead workers (p < .001), which was the result of considerably higher lead exposure during 1940 to 1960. Lead concentrations in calcaneus in active lead workers were significantly higher than in tibia when expressed in ug of lead per gram of bone mineral, which suggests a quicker absorption over time in this mainly trabecular bone. The estimated biological half-times were 16 y in calcaneus (95% confidence interval [95% CI] = 11-29 y) and 27 y in tibia (95% CI = 16-98 y). A strong positive correlation was found between lead concentrations in calcaneus and tibia for all lead workers (r = 0.54; p < .001). A strong positive correlation was also found between the bone lead concentrations and the cumulative blood lead index. Blood lead, at the time of study, correlated well with bone lead concentrations in retired--but not in active--workers, reflecting the importance of the endogenous (skeletal) lead exposure. The findings in this study indicate that bone lead measurements by XRF can give a good index of long-term lead exposure. Tibia measurements offer a higher precision than calcaneus measurements. The method is of particular interest in epidemiologic studies of adverse health effects caused by long-term lead exposure.

Adult↗
PubMedDate not supplied

The feasibility of measuring manganese concentrations in human liver using neutron activation analysis.

Manganese is an element which is required by the human body. However, as with most metals, in large amounts manganese can be toxic. People who suffer from severe manganese intoxication have symptoms similar to those of Parkinson's disease. Preclinical symptoms of manganese intoxication have recently been detected in individuals working in industries which have manganese dioxide dust in the air. The concentration of many toxic elements can be measured in vivo using neutron activation. A small dose of neutrons is delivered to the organ of interest, the neutrons are readily captured by the target nuclei, and the gamma rays given off can be detected outside of the body. A neutron activation analysis system is being developed to measure manganese concentrations in humans. The McMaster KN-accelerator supplies the neutron beam and the thermal neutron capture reaction 55Mn(n,gamma)56Mn is used. The half-life of 56Mn is 2.58 hr and thus counting can occur after irradiation. The 847 keV gamma ray given off when 56Mn decays is detected using a Nal detector. Calibration curves are made using phantoms with known concentrations of Mn. This system will be used to monitor manganese levels in individuals who have occupational exposure to the element. Preliminary measurements, using liver phantoms, give a minimum detectable limit for Mn in the liver of less than one part per million, which is well below normal levels.

Animals↗