Air pollutants generated from traffic andindustrial plants are believed to be one of the major causes of DNA damage inliving species. As a result of rapid urbanization, air pollution andenvironmental quality deterioration have been affecting our daily lives as wellas the nature. Several experimentalstudies have reported that lead has a moderate genotoxic potential.In a study conducted byValverde and colleagues ,(26) a lead inhalation model in mice was used todetect the induction of genotoxic damage as single-strand breaks andalkali-labile sites in several mouse organs (nasal epithelial cells, lung,whole blood, liver, kidney, bone marrow, brain, and testes), assessed by thecomet assay. Following single and subsequent inhalations, differences werefound among the organs studied. A positive induction of DNA damage in the liverand the lung after a single inhalation was observed. The response was positivein all organs, except the testicle, in subsequent inhalations. DNA damageinduction over time varied for each organ.
The brain and bone marrow showed thehighest damage induced. Differences in DNA damage occurred in organs when leadwas administered acutely or sub-chronically. Our study revealed a significant increase in the blood lead level of study group and controls ( p value 0.000). The mean pb inour study was 18.76±8.8 and controlsmean pb was 12±3.
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5 as compared to study in Islamabad that was carried out in2005 in which blood lead levels of wardens were 27.27 ±4.04 and a similar studyon traffic wardens in Karachi indicateda value of lead in wardens of 47.7±15.
8.micrograms/dl.Another study in Alexandrria Eygpt reported that their traffic constables had a higher blood leadlevel than our study (27).
Blood lead levels wereanalyzed in Nigerian traffic wardens, comprising sixty from Lagos , thirteenfrom the sparsely populated university town of Ile-Ife and a control group oftwenty-four subjects . The mean lead level in Lagos wardens was 18.1 ± 6.
4 ?g/dl,which was significantly higher than the level of 10.2 ± 2.7 ?g/dl in Ifewardens and 12.9 ± 7.0 ?g/dl obtained in the controls (P <0.001). However, there was no significant difference between the levels ofblood lead in Ife traffic wardens and normal controls (28)Nigeria wardens had almost similar values as our study but their study was conducted 17 years ago and since that time urbanization andpopulation has increased tremendously. Alexandria and Karachi both arepopulated cities and have more traffic congestion that is why their lead levelswere high as compared to our study.
Also after 2005 when the law of using unleaded petroleum was introduced no study had been conducted since then on this occupationally exposed group. Our study indicatedthat law had actually been implemented that has reduced lead from theatmosphere and from this exposed group.The mean age in cases inour study was from 24-39 years and in controls was 25-35 years. There was nodifference statistically in the mean age of cases and controls in our study (pvalue 0.241). The mean age of wardens in the study of Islamabad and Karachi hada mean value of 21-45 years and 20-52years respectively, not comparable with our study .The various parametersof comet assay that is Mean tail moment ,% DNA in tail and Mean tail length inour study had values of 0.
0583 ±1.960 (pvalve 0.04),4.101 ±5.87 (p value 0.136) and7.156 ±12.
56 (p value 0.003)respectively in cases and 0.045±0.108,2.055 ±2.481 and 1.
50±2.12 respectively in controls. There was a significantcorrelation of lead with TM , but no statistically significant correlation oflead with tail length in cases. The mean % DNA in tail in cases gave a mildpositive correlation with lead.The other parametersgiven in our study were % DNA in head with a difference in the mean value ofcases and controls with a (p value 0.16). The % DNA in head gave a mildnegative correlation with lead in cases (p value 0.03 and rho -0.
380). Cometlength in our study had a difference in the means of two groups having a pvalue 0.005 that was statistically significant but it gave no significant correlationwith lead in cases.A study of DNA damage by comet assay in Traffic wardens in China (29)showed that occupational exposure totraffic exhaust significantly increased tail length 4.20µm , (3.98 – 4.42) µm in outside ones vs.
3.23 µm, (2.82 – 3.7) µm in office work policemen, P < 0.001. The p valueof mean tail length is 0.
003 in our cases and controls that is statisticallysignificant and comparable to their study however our study did not give asignificant correlation of lead withtail length in cases.The results confirm thatinhaling lead induces systemic DNA damage, but certain organs, such as the lungand the liver, are special targets of this metal, partly depending on theduration of exposure.
