Biomedical subjects

J L Pirkle

Publications and source records attributed to J L Pirkle.

39 records · Page 3Linked to original sources

PubMedDate not supplied

Improving exposure assessment by monitoring human tissues for toxic chemicals.

Typically, the availability of appropriate data to estimate human exposures to toxic chemicals is scarce. Consequently, exposure assessments are often based on indirect surrogates of exposure, such as a combination of questionnaire data on time-activities and concentrations of toxic chemicals measured in environmental media (e.g., air, water, food, soil, dust). Recent advances, however, make it technically feasible and relatively affordable to measure low levels of multiple toxic chemicals in accessible human tissues (e.g., blood, urine). The increasing availability of biological markers for exposure, along with improvements in pharmacokinetic understanding, present new opportunities to estimate exposure from human tissue measurements and from knowledge of intake and uptake parameters. Biological monitoring provides exposure information that is usually complementary to the type of exposure information obtained from environmental monitoring. Biological and environmental monitoring can be used separately or together in order to meet desired objectives. We present here a discussion of the value of biological monitoring for improving exposure assessment. We emphasize the role of biological monitoring in identifying high-priority exposures, evaluating the effectiveness of intervention and prevention efforts, identifying at-risk subpopulations, recognizing time trends in population exposures, establishing reference ranges of tissue concentrations, and providing integrated dose measurements.

Environmental Monitoring↗

PubMedDate not supplied

The reliability of the serum dioxin measurement in veterans of Operation Ranch Hand.

A study was conducted on the reliability of the serum dioxin measurement of enlisted Ranch Hands veterans participating in the Air Force Health Study using paired serum dioxin measurements. The 46 veterans were not randomly selected, but their demographic characteristics, health, and dioxin levels were similar to those of 404 other enlisted Ranch Hand veterans who had a single dioxin measurement made in 1987. The average time between the measurements was 0.61 years, the first measurement made from blood drawn on 10 April 1987 and the second from blood collected at a subsequent physical examination. In original unit, the coefficient of reliability was 0.87 (95% confidence interval: 0.76, 0.94) when the first measurement was at or below 50 parts per trillion. The measurement had no reliability in original units when the first measurement was greater than 50 parts per trillion. After a logarithmic transformation, the coefficient of reliability was 0.96 (95% confidence interval: 0.93 to 0.98). These results suggest that the serum dioxin measurement should not be used in original units for any purpose when the value exceeds 50 parts per trillion. The measurement is, however, highly reliable after a logarithmic transformation over the entire range of concentrations. Other studies using the same analytical method to measure dioxin in serum could similarly benefit if the measurement used is on the natural logarithm scale.

Aerospace Medicine↗

PubMedDate not supplied

Serum dioxin levels in Seveso, Italy, population in 1976.

On July 10, 1976, an explosion at a chemical plant near Seveso, Italy, released a mixture of chemicals, including 2,3,7,8-tetrachlorodibenzo-p-dioxin and 2,4,5-trichlorophenol. As a result, several thousand people in the Seveso area may have been exposed to those chemicals. At that time, human exposure assessment was based primarily on soil levels of 2,3,7,8-tetrachlorodibenzo-p-dioxin. Medical examinations of this potentially exposed population and control subjects were begun in 1976 and in some cases continued until 1985. In 1988, we began assessing human exposure in this population by measuring 2,3,7,8-tetrachlorodibenzo-p-dioxin in small volumes of serum specimens remaining from the medical examinations. As expected, we found that the median serum dioxin levels were highest among people who lived closest to the explosion and were progressively lower among groups living farther away. These measurements have allowed us to assess exposure more accurately among individuals in this population and to relate exposure to various health effects. We found that some individuals in the exposed population had among the highest serum dioxin levels ever reported, yet chloracne was the only unequivocal effect found; cancer risks are still being investigated. We also found that other individuals with as high or higher serum dioxin levels did not develop chloracne. We also found that the serum half-life of dioxin in this population was 7-8 years, which agrees with other findings although we do report some differences in the serum half-life of TCDD for women and children. We also observed an increase in the percentage of female newborns to parents who resided in Zone A at the time of the explosion, and we also report on the 1976 serum dioxin levels in people who later developed cancer.

Accidents↗