Objective: In China, significant levels of environmental pollution, substandard worksite quality and high rates of smoking predispose the population to potentially high risks of respiratory illnesses and other diseases. We assessed the prevalence of respiratory symptoms and their risks in relation to personal, occupational and environmental risk factors in a heavy-industry province of northeastern China. Methods: Lifestyle, health, residential and occupational data were obtained in 2002 from 31,704 adults of six cities in Liaoning, China, using self-assessment questionnaires. General linear and multi-level models were used to evaluate prevalence rates and risks of respiratory symptoms, related to both individual and combined exposures to environmental and occupational risk factors. Results: The crude prevalence rates (PRs) for persistent cough, persistent phlegm, wheeze and asthma were 2.3, 3.8, 2.1 and 1.0%, respectively. The odds ratios (ORs) of all four respiratory symptoms examined were increased by: smoking (ORs from 2.06 to 5.02), occupational dust (ORs from 1.35 to 1.72), occupational gas (ORs from 1.48 to 1.72) and presence of irritating smoke during cooking (ORs from 1.54 to 2.22). An index combining proximity of residence to road, factory or chimney, indoor coal use and presence of irritating smoke during cooking was associated with up to 3.9-fold increased risks of all symptoms. Increasing values of each risk factor were generally associated with dose-response trends in prevalence rates and risks (all p for trend <0.01). Conclusion: The crude PRs of symptoms were lower than those reported by European and American studies but closer to those of previous Chinese studies. The risks of respiratory symptoms in this population were increased by smoking, occupational exposures to dust and gas, and combined residence-related exposures such as living close to a main road, factory or chimney, indoor coal use and the presence of irritating smoke during cooking, among other risk factors.
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