A ["prospective", OR "retrospective"] cohortstudy is carried out to investigate the association betweenoccupational arsenic inhalation and neurological exposure andneurological effects among workers in a copper smelter. For thesake of simplicity, let’s assume there are two possible exposurecategories: high and low (for example, those working in thesmelting process and those working in administration). The exposurewas carefully assessed by review of company records which reflectedvery good exposure monitoring (both air sampling and urinetesting). The outcome was based on self-reported information froman interview that asked: “Have you had tingling in your fingers inthe last month that lasted more than 30 minutes?” Those that said“yes” were classified as “diseased”, and those that said “no” werethe “non-diseased” group. In order to avoid ["informationbias", OR "selection bias"]   bias, the companyencouraged everyone to participate by telling their workers thatthey were a concerned employer and wanted to know if there wereadverse neurological effects from the potential arsenic exposure insome of the work areas.

The following is the resulting 2 x 2 table:

	Diseased	Not Diseased	Total
High Exposure	60	100	160
Low Exposure	40	350	390
Total	100	450	550