Atmospheric toxic gases and their probable impacts on public health and crop production

Abstract

Bangladesh ranked fourth among 91 countries with the worst urban air quality in the latest air pollution monitoring report by the World Health Organization. Data from the National Institute of Diseases of the Chest and Hospital shows that nearly seven million Bangladeshis suffer from asthma and more than half of them are children. In Dhaka alone, an estimated 15,000 premature deaths, as well as several million cases of pulmonary, respiratory and neurological illness are attributed to poor air quality. Experiences from other countries of the world suggest that plants exposed to air pollution over an extended period grow at a slower rate, produce fewer blossomless and are more susceptible to disease and insect damage. In addition to physiological damage, ground level ozone may cause reduced resistance in crop plants to fungi bacteria, viruses and insects, reducing growth and inhibiting yield and reproduction. Chlorossis (yellowing) and a gradual bleaching of the surrounding tissues fairly common in crop plants. Bangladesh is lacking systematic ambient air quality measurements and time series data though the reports based on sporadic analysis indicate worsening air pollution in particular, in cities with heavy traffic movement and congestion, industrial and brick-kiln actives and solid waste management practices. The level of air pollution and the effects on human health and crop plants were however, not assessed to that extant. With this background atmospheric toxic gas concentrations namely, O, CO, SO, TVOC, NO, NO, HS, NH in the ambient air were measured in some selected hot spots in Dhaka city between 2009 and 2011. The results were compared with some selected peri-urban, semi-urban, rural areas and St. Martin’s Island at the Bay of Bengal as base-line. Significant level of diurnal and seasonal variations of toxic gases were also observed. A survey on human health and damages on crop plants and/or trees using structured questionnaire reveal that the people in Dhaka city are experiencing health problems like breathing problem, eye-irritation, cough, asthma, vomiting, headache in particular, women and children appears to be the mostly affected. More than 40 percent women and children interviewed in Dhaka city reported to have been suffering from eye-irritation, cough, asthma, vomiting, headache and other respiratory problem. Regarding damages on crop plants and/or trees, 60 percent of the people interviewed reported that they are having damages on crop plants in the form of chlorosis of leaves, crop damages, top dying of tree species, spotted fruits (guava), small size fruits and reduction in yield (20% for rice, 25% for fruits) and loss of leaves on road-side trees. No direct relationship to the damages on crops or effects on human health with any of the particular toxic gases measured could be established.