Indoor air pollution and respiratory symptoms among fishermen in the Niger delta of Nigeria

Victor A Umoh, University of Uyo; Etete Peters, University of Calabar; Gregory Erhabor, Obafemi Awolowo University, Ile-Ife; Essien Ekpe, Federal Neuro-Psychiatric Hospital, Calabar; and Andrew Ibok, University of Calabar Teaching Hospital, Calabar; all in Nigeria. Correspondence to: Victor A Umoh, Department of Internal Medicine, University of Uyo, Uyo, Akwa Ibom State, Nigeria. Email: [email protected]. Abstract Biomass is heavily depended on for domestic energy use by people in developing countries. Combustion of these materials produces a lot of smoke. Exposure to this indoor air pollution has been linked to a number of respiratory disorders. The aim of our study was an assessment of the long-term respiratory effects of indoor air pollution. A survey was conducted in the riverine areas of the Niger Delta of Nigeria among 521 fishermen exposed to indoor air pollution from burning firewood and 545 matched controls. Exposure was determined by the product of the average daily duration of time spent close to the fire and the number of years (hours–years). A modified British Medical Research Council (BMRC) questionnaire was used to obtain information on respiratory symptoms and spirometry was performed on the participants. The frequency of chronic respiratory symptoms was significantly higher among the exposed fishermen compared with the control subjects. Chronic bronchitis was significantly associated with an obstructive ventilatory pattern. Logistic regression analysis showed an increased risk for chronic bronchitis among exposed fishermen (OR 8.7; 95% CI 4.7–16.3, p<0.001); women were six times more likely than men to develop chronic bronchitis (OR 6.6; 95% CI 2.5-17.8, p< 0.001); and cigarette smokers were five times more likely than non-smokers to develop chronic bronchitis (OR 5.0; 95% CI 1.8–13.8, p<0.05). The results of this survey showed an association between exposure to indoor air pollution and chronic respiratory disorders. Cigarette smoking aggravated this association. Introduction Approximately 50% of the world population, and up to 90% of the population in developing countries rely on burning biomass fuels for everyday household energy needs.1 Often, the stoves have poor combustion capacity and can utilise only a fraction of available fuel energy.2 These stoves produce heavy smoke and release a number of harmful pollutants.3 The use of biomass for cooking and heating usually takes place in poorly ventilated homes.4 The fires are kept going for many hours a day thus exposing the occupants to years of daily smoke.5 Several studies have documented pollution levels in such homes,6,7 and these levels may be up to 200 times higher than recommended levels.8,9 The health effect of indoor air pollution is determined not just by the pollution level but also by the time people spend breathing polluted air.10,11 Thus exposure to indoor air pollution from the combustion of biomass fuels constitutes a significant public health hazard affecting predominantly poor communities in developing countries.12,13 Exposure to indoor air pollution has been linked to a number of respiratory illnesses, including acute respiratory infection,14,15 chronic bronchitis,16,17 asthma,18 chronic obstructive pulmonary disease (COPD),19–21 tuberculosis,22,23 and possibly lung cancer.24,25 In Nigeria, World Health Organization (WHO) estimates put biomass fuel use at 67% for the year 2002 and the total deaths attributed to indoor air pollution from biomass smoke at 79 000.26 Few studies have examined the acute effects of exposure to indoor air pollution and fewer still the longterm consequences. Previous studies by Peters et al27,28 and Akani et al29 have shown that exposure to indoor air pollution from biomass smoke is associated with an increase in the frequency of acute respiratory symptoms. This study was, therefore, undertaken to examine the relationship between long-term exposure to indoor air pollution from firewood smoke and chronic respiratory disorders among fishermen.