Indian Pediatrics 1999; 36:303-306 

Blood Lead Levels in Urban and Rural Indian Children

Lead was one of the first metals known to man and Lead tetraethyl was introduced in 1923 as an 'antiknock' agent in petrol. Soon it was recognized as a "poison". Chronic lead exposure is linked to irreversible adverse neuro-developmental effects in children(l-6). Most developed countries introduced un­leaded petrol to control the impact of atmo­spheric pollution on the lead levels in children and adults in the last decade. Many automobiles are manufactured to run only on unleaded petrol. Fortunately the prevalence of chronic lead toxicity has decreased since the introduction of laws restricting use of leaded petrol in these countries(1). The Indian government, (along with other countries like China), have been slow in implementing these measures. Hence we undertook this study to determine the prevailing lead levels in chil­dren in southern India and also to see if there were any differences between urban and rural children.

Subjects and Methods

The study was carried out in children aged between 5 and 15 years in the city of Davanagere (served by three major teaching hospitals - children attending the hospitals comprising both rural and semi-urban) and Bangalore (IT! Hospital - mainly urban children) in South India. A total of 150 children attending the Out Patient Department for vari­ous ailments were selected randomly and ver­bal consent was obtained both from the child and the parent/parents. A detailed history was elicited with particular emphasis on the personal details, complaints, dietary habits, history of pica, symptoms suggestive of altered behavior, blood transfusions, history of pain abdomen, constipation, delirium and convulsions. The history also included questions on the place of dwelling, proximity to factories or battery works; vehicle ownership and a family history of diseases. Each child underwent a detailed medical examination to detect any occult signs of lead poisoning like anemia, anorexia, alopecia, Burtonian line (lead line) on gums. A heparinised blood specimen was collected for blood lead level estimation. Precautions were taken to Clean the skin and not to squeeze the arm while taking blood which could affect the results.

The blood samples were analyzed by dithizone method for blood lead level and the result was expressed in terms of micrograms/ dl. Dithizone method is a calorimetric method of estimating lead level and these days estimation of lead level is done by atomic absorption method for its accuracy. Since our study was a screening study, we used dithizone method which is more economical and less tedious.

Results

One hundred and fifty children were recruited into the study. There were 25. urban children (Bangalore), 75 semi-urban subjects (Davanagere) and 50 rural children (Rural Davanagere). Eighty eight (58.7%) children were boys and 62 (41.3%) were girls. The blood lead levels ranged from 13 to 43 μg/dl with the average being 24.1 μg/dl (N = 10 to 40 μg/dl) (Table I).

The differences in the mean (average) blood lead concentrations were statistically significant. (p <0.001), with urban, semi-urban and rural population showing significant differences. Lead levels were higher in the age groups 8 to 11 years (mean 32.0 μg/dl) and 12 to 15 years (mean 29.6 μg/dl) as compared to those under 7 years (mean 19.2 μg/dl). The age related differences in blood lead levels were also significant for urban, semi-urban and rural children with most children aged 8 years or over having significantly higher values compared to children under 7 years. The mean blood lead levels did not differ statistically by gender (boys - 24.2 and girls - 23.9 μg/dl), even after taking account of region and age. No clinically overt cases of lead poison­ing or lead encephalopathy were documented.

Discussion

Lead has been known to mankind for more than 3000 years and its harmful effects are now known for nearly 300 years. Early writings describe lead colic and its association with lead mining and refining. Hippocrates (460 to 357 BC) described plumbism as a result of working in the smelting of lead ores and other metal ores. We have come a long way since then in recognizing the harmful effects of lead(7). Over the recent years, blood lead levels once considered to be safe have now shown to be of public health concern. National campaigns promoting the use of un­leaded petrol and other steps to reduce the use of lead in the community and to heighten public awareness of sources of exposure are in place in many countries(8).

TABLE I

Blood Lead Levels

The lead levels in our setting, especially in urban children, seem to be approaching the upper limit of the normal range. This may be related to excess of lead in the atmosphere, arising from automobile gasoline exhaust Though most children had no symptoms, they could suddenly go into acute lead poisoning in the future or else their scholastic performance may come down with increased industrialization and increase in the number of automobiles in the future( 1,4,5).

We also noticed that significant number of children from urban areas had family history of hypertension, especially the ones with higher level of lead levels in the blood. Could lead be one of the precipitating factors of essential hypertension' in the affluent and urban population(9)?

There is abundant evidence that higher lead levels are associated with behavioral problems, cognitive defects and mental handicap in children( 1-5, I 0, 1 I). Our study was carried out to see any difference in blood lead levels in urban children associated with increased automobile exhaust and air pollution and hence psychological assessment of these children was not part of our study. In addition, there are reports of lead being a content in many Ayurvedic medicines which could also be contributing to this epidemic(12). With so much industrialization, India still is slow to adopt unleaded petrol throughout the country though it has been made available in the metropolitan cities in the recent past Japan and Brazil are the only two countries so far who have achieved 0% levels in elimination of the use of leaded petrol and many other countries are expected to follow suit International organizations like WHO, UNICEF and professional bodies like International Pediatric Association, should put pressure on the responsible governments to take necessary steps to control this silent epidemic.

Acknowledgement

The authors would like to acknowledge Mr. Leigh Blizzard, Medical Statistician for his help in statistical calculations.

 References