Reporting bias related to an environmental hazard.
During spring 1984, second and fifth grade schoolchildren living in three Haifa Bay areas on the eastern Mediterranean coast, with different levels of air pollution, were studied. The parents of these children filled out ATS-NHLI (American Thoracic Society and the National Heart and Lung Institute) health questionnaires and the children performed PFT (Pulmonary Function Tests). A trend of higher prevalence of most reported respiratory symptoms was found for schoolchildren growing up in the medium and high polluted areas as compared with the low pollution area. Logistic models fitted for the respiratory conditions that differed significantly among the three residential areas also included background variables that could be responsible for these differences. Relative risks for respiratory conditions calculated from these models were in the range of 1.38 and 1.81 for children from the polluted area as compared to 1.00 for the low polluted area. All the measured values of PFT were within the normal range, with no consistent reduction in PFT for any residential area. During spring 1989, seventh graders (second graders in 1984) were reexamined and a new cohort of fifth grade children was studied, using the same techniques as in 1984. A very significant rise in the prevalence of most reported respiratory symptoms and diseases was observed among both fifth and seventh grade schoolchildren in 1989 compared to 1984, especially in the low and medium polluted areas and less in the polluted area. Changes over time in PFT in the older cohort were similar in the three areas. PFT of fifth graders in 1984 and in 1989 were very similar. The most significant factor in logistic models fitted for the prevalence of respiratory conditions among the studied schoolchildren in 1989, was the subjective attitude of their parents towards the deleterious effects of air pollution on their children's health, and the subjective estimate of their children's exposure to pollution rather than measured exposure. A huge campaign carried out during the survey against the main polluters in the Haifa Bay area caused both public concern and apparently reporting bias.