Mental retardation and parental occupation: a study on the applicability of job exposure matrices

In a case-referent study on mental retardation and parental occupation, the applicability of job exposure matrices for the identification of risk factors was evaluated. The parents of 306 mentally retarded children (cases) and 322 referents were interviewed about their occupational activities in the pregnancy period. Detailed occupational histories were obtained that were compared with exposures generated by two different job exposure matrices. The agreement between interview and matrices was low: the sensitivity ranged from 17.9% to 32.4% and the percentages of false positive exposures from 66.7% to 96.0%. By means of the interview, significantly increased odds ratios (ORs) were found for exposure of the mother in late pregnancy to radiation (OR = 9.3), mercury (OR = 8.7), organic solvents (OR = 1.7), hair cosmetics and dyes (OR = 3.7), paint (OR = 2.7), hexachlorophene/phenylphenol (OR = 3.1), antibiotics (OR = 2.9), and dust (OR = 2.2) and for working with copying machines (OR = 3.0) or in occupations with poor climatological circumstances and permanent contact with people. The last was confirmed by the British matrix (OR = 1.7). Otherwise, most of the mentioned associations were missed by the job exposure matrices. Therefore, these matrices were not considered to be applicable in this particular study, nor in most other reproductive epidemiological studies in view of their general properties and limitations.