3.6 Lead:

Leads content (as Pb) in motor Gasoline available in Bangladesh:

Besides posing and immediate health risks through inhalation, vehicular lead emissions also accumulate in soil, enter the food chain, contributing to exposure through ingestion over long period of time. Food sold in the open air along city streets has been found to contain high level of lead.

Currently, the World Health Organization suggests that a level of 20 microgram of metal per deciliter of blood (20 micro gram/dl) is the maximum acceptable concentration. Other studies consider that the detrimental effects of exposure to lead appear at concentration of between 10 and 15 micro gram/ dl. The body tends to accumulate lead over a lifetime and can release it only slowly. Hence even exposure to small concentrations of lead over a long period can produce harm. It is the total body burden of lead that is related to adverse effects.

Bangladesh Atomic Energy Commission recently expresses their alarming study finding that the quantity of lead in air of Dhaka city is 463 nanogram per cubic meter. Available information from similar research work in other parts of the world would have found lead concentrations of 383 nanogram in Mexico city, 360 nanogram in Bombay, 333 nanogram in Sydney, 230 nanogram in Santiago, 70 nanogram in Los Angles whilst in Kyoto the presence of lead in air is at 40 nanogram, the lowest. So the lead pollution of Dhaka city has passed even the Mexico City which is considered to be the most polluted city in the world. According to an estimate made by BAEC, 50 tons of lead is emitted in Dhaka air annually and emission reaches its highest level in the dry season, from November to January.

Department of Environment has also conducted a study for lead level in three different areas of Dhaka city form November '96 to March '97 and found 122.78 to 251.84 nanogram /cu meter at Farmgate area. At the same time it was 61.18 to 75.73 nanogram /cu.m in Tejgaon Industrial Area and 1.26 nanogram /cu.m in Lalmatia Housing Area. Though the accepted level of lead for Bangladesh has not yet been settled but result is very alarming (Ref: Report on Air pollution in Dhaka city by Department of Environment '98).

In a study conducted to determine the level of lead in water, soil and fish of Dhanmondi lake of Dhaka city found average total aqueous lead concentration varies from 151 to 210 m g/l during dry season and 30 to 120 m g /l during wet season. Lead concentration in aqueous media was found to be much higher than that specified by Environmental Quality Standard in Bangladesh (EQS) for fishing and drinking (50 m g /l), industrial (100 m g /l) and irrigation (100 m g /l) purposes. Significant amount of lead was also found in various tissues of fish of Dhanmondi Lake, located at the central part of the Dhaka City.

Recently a descriptive cross sectional study have been conducted by a researcher of Department of Occupational and Environmental Health of NIPSOM on Rickshaw pullers, Baby-taxi drivers, Traffic police, Tempo assistants, Petrol pump operators and motor vehicles serving men of some selected areas of Dhaka city. In this study it was found that, the mean blood lead levels of Rickshaw pullers was 248 m g /dl (range 154-344 m g /dl), of Baby Taxi drivers 287 m g /dl (range 161-372 m g /dl), Traffic polices 272 m g /dl (range 152-32 m g /dl). Tempo assistants 255 m g /dl (mean 177-49.9 m g /dl), petrol pump operators 249 m g /dl (mean 177-314 m g /dl) and Motor vehicles serving men was 264 (mean 207-342 m g /dl). The mean blood lead level on of among all these risk group was found to be higher than the accepted value. The traffic police group was the worst affected. The study also noted that blood lead levels increased with the duration of exposure. It was also observed that there was a relationship between increased blood lead levels with some signs and symptoms of respondents exposed.

Countries around the world are at various stages of tackling the problem of human exposure to traffic related emission. Lead has been totally phased out from gasoline in several countries including Australia, Austria, Brazil, Canada, Japan, Sweden, Thailand and the USA.

Various technological options are available to increase use of octane gasoline without using lead by modifying the petroleum refining process. The use of oxygenates, as well as isomerisation and alkyation are ways of substituting lead. As in Dhaka City two strokes engine vehicles are the major culprits of emission of lead. Government of Bangladesh has already imposed ban on importing two stroke engine. In the road signals posts it is observed that the drivers of the motor vehicles do not stop their vehicles. In the developed countries it is a common practice to stop the vehicle deadly in the signal posts. When the post gives the yellow signals drivers start their engine and getting green signal they run. These should be practiced in our country also. This will reduce environmental pollution and even accident.

People should be motivated to compressed natural gas and lead free fuel. Motor Vehicles Ordinance '83 and Environment Protection Act '93 should properly enforced. Lastly People's awareness should be increased about environment pollution and to move against lead poisoning through motor vehicle emission.
 
 

VOCs contribute to the formation of ground-level ozone, with the deleterious effects noted above. A number of VOC's are also toxic and are described under Hazardous Air Pollutants.

Automobile exhaust fills the air in Dhaka City with Volatile Organic Compounds beyond tolerable limits, with some of the compounds causing cancer.

Recently, Prof. Abul Hussam of George Mason University, Virginia USA, detected 200 organic compounds and identified 35 of those by analyzing four air samples collected from the Shewrapara of the city. It was the first such advance analysis of air quality ever done in Bangladesh. The air samples were analyzed at the time of installing ultramodern equipment at a privately setup research, development and technology center in the area on August 18 and 19, 1998. The test showed that the exhaust of auto rickshaw contain VOCs, four to more than seven times beyond the allowable limit. The ambient air in Shewrapara contains these compounds close to threshold limit, the test revealed.

Prof. Hussam said the analysis of exhausts of auto-rickshaw showed the presence of toluene, a cancer causing agent, up to 200,000 micrograms per cubic meter as against the threshold limit of 2000 micrograms per cubic meter. The 35 volatile organic compounds identified included cancer causing agents: benzene, toluene, octane, ethylbenzene, 1-isocyanato-3-methoxybenzene, p-xylene, propylbenzene, trimethylbenzene and butylbenzene. The test, however, were conducted at a less vehicular traffic congested area in the metropolis. Prof. Alauddin said that a much higher concentration of air pollutants would be found if tests were carried out at heavily automobile congested areas like Hatkhola, Shapla crossing, Sonargaon crossing and Farm Gate. Prof. Hussam, said that apart form automobile exhausts, natural gas (if cookers are on), chemical processing plants, and biogenic sources contribute to the extremely bad VOC pollution of Dhaka’s air.