BLOOD LEAD LEVELS IN A POPULATION EXPOSED TO VEHICLE EMISSIONS

Over 99% of atmospheric lead in urban areas is due to petrol lead emissions. Blood lead levels in traffic policemen, street vendors, drivers of three wheelers, motor cyclists and school children in the Colombo metropolitan area were studied. Some of the general population who are least exposed to vehicle emissions were used as controls. They were selected from a village in Mirigama area after interviewing. Atomic absorption spectrophotometric method with graphite tube atomization was used to analyse venous blood lead levels. The study showed significantly higher levels of lead in blood for the adult population who are exposed to vehicle emissions than controls. Blood lead levels were established as, Control (90 pg dm-3) < Motor cyclists (120 pg dm3) < Street vendors (130 pg dm3) < Drivers of three wheelers (150 pg dm3) < Traffic policemen (530 pg dm3).


INTRODUCTION
Lead is added to petrol in the form of tetraethyl lead (TEL) and tetramethyl lead (TML) in Sri Lanka, while some of the other countries use nonileaded petrol.Diesel does not contiin added lead.During' the combustion of petrol lead is released into the atmosphere, principally as inorganic lead salts in aerosol form1 that remain suspended in air for some time:before settling.Thus people can breathe the lead directly, or through the polluted dust in'the 'air.
It has been reported that there is a close relationship between lead levels in blood and petrol emissi0ns.lTherefore this work was carried out to assess the blood lead levels of the population exposed to vehicle emissions.Unpublished data by Mathes et al. indicates that the average lead concentration in ambient air of Colombo Metropolitan area ranges between 0.20 to 0.55 pg m-3.By considering these values the sampling areas were selected.The objective of this study was to assess for the first time, the blood lead levels of selected groups of population that are exposed to vehicle emissions within the Colombo metropolitan area.

rnTHODS AND MATERIALS
Traffic policemen, street vendors, drivers of three wheelers, motor cydists and school childrenin the Colombo metropolis were studied.The analysis ofthe blood lead levels of the general population who are presumably least exposed to vehicle The main findings of this paper were presented a t the 51st annual session of Sri Lanka Association for the Advancement of Science, November 1995.emissions was performed separately for comparison.This control group was selected from a village in Mirigama area after interviewing them.Eventhough the selection of subject groups was judgmental, random samples were collected within a given group.Since blood collected by venipuncture has a low likelihood of contamination compared to blood collected by fingerprick, venous blood was the preferred specimens for analysis and was used throughout the project.Atomic absorption spectrophotometric method with graphite tube atomjzation was used for measuring p r ~c e d u r e .~ All reagents used in this work were analytical grade or better.All glassware including sample bottles were cleaned thoroughly.High quality lead standard solution was used for instrument calibration (BDH spectrosol grade 1000 mgll).
All venous blood samples were taken by a medical officer with 'precisionglide' sterile disposable syringes with 23 gauge needles.A venous sample of 2-3 ml human blood was taken from the test person.Immediately after sampling the blood was thoroughly mixed in pre-cleaned glass bottles with 4 mg of EDTA (anticoagulant) per 1 ml of whole blood.The samples were swirled for 1 minute and stored in ice and transported to the laboratory.1.0 ml aliquot of blood and 1.0 ml of the matrix modifier Triton -X 100 (an alkyl phenoxy polyethoxy ethanol) were vigorously mixed by means of an electrical mixer for few minute^.^The samples were analysed on the same day or day after using electrothermal atomization.10.0 pL aliquot of these mixtures was directly injected into the instrument.Triplicate measurement of each standard and sample was performed.The volume of the matrix modifier was changed in certain cases due to the high concentration of lead present i n blood samples.Preliminary measurements were made in order to set up the best instrumental conditions.Prior to sampling the consent of all the adult subject groups were obtained.Only the voluntary blood donors were sampled.For school children written consent of their parents was obtained before the sampling.
To set up the best analytical conditions for the drying and ashing steps, some preliminary measurements were made.Temperature and duration of the drying period were found to be crucial factors to avoid splattering.For 10 pL samples the following temperature progrmme was used throughout: Step

Subject Group
No. Age

62-73
Not applicable with the increase in age there appear to be a reduction in the lead uptake.This may be because there is a slightly higher intake of lead into the blood in the younger group4and perhaps the older policemen spent less time on duty.All the subject groups showed significantly higher levels of lead in blood a s compared to controls (Table 3).The traffic policemen showed very high levels oflead in blood.
In the absence of a suitable control group for school childrenit is difficult to make a conclusive statement.However in the broad sense, compared to a recent study4 the lead in blood ( < 90 pg dm-3 ) for school children could be reasonably stated to be on the lower side.Comparison of the lead levels in blood with the WHO value indicated the significantly higher levels of lead in certain subject group as indicated by the Table 3.