These studies provide information about possible risks of medications or other exposures in human pregnancies. Concentration risk can arise from uneven distribution of exposures (or loan) to its borrowers. The NIOSH Manual of Analytical Methods contains methods for measuring occupational exposures to beryllium. Significant uncertainties exist for the health effects of low-dose exposures. Chemical leukoderma is a similar condition due to multiple exposures to chemicals. There is substantial evidence of associations between organophosphate insecticide exposures and neurobehavioral alterations. Nevertheless, mesothelioma may be related to brief, low level or indirect exposures to asbestos. Both routes provide equal drug exposures and generally comparable therapeutic efficacy. HDR+ takes continuous burst shots with short exposures. Little evidence exists to support associations with specific environmental exposures. It is expressed as a percentage of a bank's risk-weighted credit exposures. It is hypothesized that this may be due to environmental exposures or lifestyle choices. Affected individuals may become independent reservoirs leading to further exposures. "Earthquake engineering" involves designing structures to withstand hazardous earthquake exposures. The resulting negative is a composite of all the individual exposures.