Clinical application of in vivo tibial K-XRF for monitoring lead stores.

We used in vivo tibial K-x-ray fluorescence for clinical evaluation of bone lead stores in 31 patients suspected of excessive lead absorption. Four clinical situations were examined: (1) postchelation therapy, (2) renal failure, (3) home exposure, and (4) occupational exposure. K-x-ray fluorescence assisted in determining the magnitude of body lead stores in patients with known excessive lead exposure. Serial measurements revealed a reduction in bone lead that occurred over the years, during which there was an absence of continued exposure; this reduction occurred more rapidly during chelation therapy. Sustained high bone lead levels following chelation therapy in two children were consistent with elevated lead stores from prior pica. In a patient with renal failure, K-x-ray fluorescence demonstrated massive lead stores at a time when chelation testing was not possible. In other cases, bone lead levels indicated the possible contribution of lead nephropathy to renal diseases of other etiologies. In individuals exposed to lead during home renovations, K-x-ray fluorescence provided reassurance that past exposure did not result in elevated body lead stores decades later. In the occupational setting, K-x-ray fluorescence documented cumulative lead stores in workers whose exposures varied in intensity and duration. The examples discussed here show how physicians can use K-x-ray fluorescence to deal with practical questions of patient management. As the test becomes more generally available, its safety, specificity, and simplicity should make it an important alternative to cumbersome chelation tests and potentially misleading blood lead measurements.

Clinical experiences: development of a medical surveillance protocol for hazardous waste workers.

Medical surveillance of hazardous waste workers is essential for the health of these workers, who have unique, complex exposures. In order for this preventive tool to be effective, the supervising and/or examining physician must be educated about the specific health risks of hazardous waste workers and also must perform a comprehensive examination. Results of testing should be evaluated both for remarkable abnormalities as well as longitudinal subtle changes in individuals, and also for trends in workers with similar exposures. Fitness for duty determinations should be then made with appropriate communication of abnormalities and follow-up recommendations to both employers and employees. To date, clinical and research findings from clinical centers performing surveillance examinations on hazardous waste workers have not revealed remarkable abnormalities related to their potential exposures. The possible causes for these results include: (1) the workers have been well protected; (2) the current diagnostic methodologies are not sensitive enough to detect pathophysiologic changes; and (3) disease may not yet be manifest due to latency or cumulative effects of long-term low-dose exposure. In addition, one must keep in mind that previous clinical and research data were collected from test results of workers who were mainly involved in feasibility, as opposed to remediation, activities. With the prospective change of more clean-up involvement of hazardous waste workers, their potential for exposure may increase. Therefore, periodic collaborative evaluation of existing surveillance programs' results (e.g., every 5 years) is advised. This would allow determination of the efficacy of the current diagnostic methods in detecting disease, as well as the possible inclusion of more sensitive and/or specific newer technologies for use on a more routine basis.(ABSTRACT TRUNCATED AT 250 WORDS)

Heat stress in hazardous waste workers: evaluation and prevention.

The risk of heat stress for hazardous waste workers is high due to the unique aspects of their work, particularly the use of vapor-barrier clothing. Such garments interfere with one of the body's principal mechanisms for dissipating heat, that is, evaporative cooling. Under such conditions the body's heat load rapidly increases and heat-related illness may occur. The medical surveillance examination is an important tool for identifying those workers with risk factors for developing heat stress or underlying diseases that may be exacerbated by heat strain. Further testing to determine fitness for duty, e.g., exercise stress testing, needs to be individualized with respect to the patient's specific work situation and/or clinical status. Appropriate medically related recommendations regarding an individual's ability to perform hazardous waste work can then be determined by the examining physician. Finally, preventive strategies, such as training, physiological and environmental monitoring in the field, judicious scheduling of work and rest periods, appropriate hydration, and use of cooling equipment and canopies, are available and should be employed to reduce the occurrence of heat-related illness in hazardous waste workers.

Medical surveillance of hazardous waste workers: conclusions and consensus.

This final article ties together some of the loose ends left behind. It also considers some of the legal requirements and addresses some of the ambiguities that relate to the medical program, as well as re-emphasizes some important issues.

Medical surveillance of hazardous waste workers: ability of laboratory tests to discriminate exposure.

The assessment and cleanup of hazardous waste sites has become a growth industry. Unlike traditional factory employment, chemical exposures on wastes sites are likely to involve uncharacterized mixtures. Medical surveillance of hazardous waste workers has become a major preventive strategy. To evaluate the effectiveness of the traditional laboratory tests employed in most surveillance programs, we compared test results in two groups of hazardous waste workers (409 males, 68 females) with responsibilities for the assessment and management of waste sites. We stratified employees into a group with a high potential for exposure ("exposed") and a group with a low potential for exposure ("unexposed"). Fifty-five clinical chemistry, hematologic, and urinalysis variables were contrasted using an analysis of variance. The only consistently significant difference was a low mean corpuscular volume in the "exposed" group. The lack of other significant findings suggests that either the true exposure status of individuals was not reflected in our classification or that the traditional tests were inappropriate or insensitive. We conclude that it is essential to evaluate surveillance results carefully and to develop protocols that are appropriate to the actual exposures encountered in hazardous waste work.