Systematic review and quantification of respiratory cancer risk for occupational exposure to hexavalent chromium.

AIM: To investigate the exposure-risk relationship for occupational chromium (VI) exposure and lung cancer in order to establish exposure limits. METHODS: We systematically searched for studies reporting on occupational Cr(VI) exposure and cancers of the respiratory tract. To be included, studies needed to provide data for more than one level of occupational Cr(VI) exposure, adequately consider the confounder smoking and be of adequate methodological quality. Because direct genotoxicity was considered the predominant mechanism of carcinogenesis of Cr(VI), linear models were applied in order to fit risk data. Relative risks were calculated based on these linear regression models and then used to estimate excess absolute risks. RESULTS: Five studies of two cohorts of chromium production workers in Baltimore, Maryland, and Painesville, Ohio, were included. Based on different estimates for the exposure effect, the absolute excess risk was found to be "acceptable" (less than 4 per 10,000 according to the German Committee on Hazardous Substances, "AGS") at a Cr(VI) concentration of 0.1 µg/m(3), and became "intolerable" (more than 4 per 1,000) beyond a Cr(VI) concentration of 1 µg/m(3). CONCLUSION: Occupational exposure limits for Cr(VI) based on excess absolute risks can be derived from published data identified by a systematic literature review.

Intracranial oscillations of cerebrospinal fluid and blood flows: analysis with magnetic resonance imaging.

PURPOSE: To detect oscillations of the cerebrospinal fluid (CSF) flow related to the heartbeat and frequencies lower than 0.6 Hz and to compare these oscillations of CSF and blood flow in cerebral vessels by using echo planar imaging in real time mode. The existence of such waves has been well known but has not yet been shown by MRI. MATERIALS AND METHODS: In a slice perpendicular to the aqueduct, CSF flow as well as CBF, could be determined in sagittal sinus, basilar artery, and capillary vessels. After Fourier analysis, four frequency bands were assigned. RESULTS: In the very high-frequency (heart rate) range, the integrals under the CSF curves were more closely related to arterial CBF than to changes in the sinus. Also, in the high-frequency (respiration rate), low-frequency (0.05-0.15 Hz), and very-low-frequency (0.008-0.05 Hz) ranges, the integrals under the CSF curves corresponded with arterial and capillary CBF. CONCLUSION: Slow and fast oscillations in CSF flow are detectable in healthy persons with a proportional allotment to arterial and capillary CBF.