Various characteristics of occupational exposures were discussed in terms of epidemiological exposure assessments for industrial hygiene research. Composition and intensity of occupational exposures varied by type of job and workplace conditions, thus complicating retrospective assessment of long term exposures. Factors affecting exposure included source, transport, worker components and setting. Two models for estimating past exposures were discussed and illustrated with an ongoing study of hydrocarbon exposures in gasoline transport workers. The source receptor model estimated exposure over time as a function of source output composition and strength, transport processes, worker position relative to source, exposure controls at source or worker and subject's work activities. Historical changes could be analyzed in terms of materials, processes or work site configuration. The task specific time weighted average (TWA) model utilized limited monitoring data with job title and work location. This model provided statistical distributions of overall TWAs for job title exposure assignments and a method for historical estimates of full shift exposures based on changes in job exposures. The TWA model was especially useful for TWA exposure extrapolations from short term task data with potential high exposures. TWA distribution was not necessarily lognormal, even when individual task exposure levels were lognormally distributed. A simple mathematical model was used to identify types of cases where statistical distributions of full shift TWA exposures were lognormal or nonlognormal. Both models were useful for assessing potential errors in exposure estimation. The authors conclude that consideration of various exposure measures is important because less quantitative measures based on nature of operations and job activities can be useful in some cases for epidemiologic assessment of etiologic hypotheses.
We take your privacy seriously. You can review and change the way we collect information below.
These cookies allow us to count visits and traffic sources so we can measure and improve the performance of our site. They help us to know which pages are the most and least popular and see how visitors move around the site. All information these cookies collect is aggregated and therefore anonymous. If you do not allow these cookies we will not know when you have visited our site, and will not be able to monitor its performance.
Cookies used to make website functionality more relevant to you. These cookies perform functions like remembering presentation options or choices and, in some cases, delivery of web content that based on self-identified area of interests.
Cookies used to track the effectiveness of CDC public health campaigns through clickthrough data.
Cookies used to enable you to share pages and content that you find interesting on CDC.gov through third party social networking and other websites. These cookies may also be used for advertising purposes by these third parties.