Introduction

Lead in drinking water is probably absorbed more than lead in food. Adults absorb 35% of the lead they drink and the absorption rate for children is greater than 50%.( 2 , 3 , 6 , 16 , 12 ). The permissible limit of lead in drinking water is 0.01 mg/l according to WHO (17) and 0.05 mg/l according to EMH (5).

Breast milk is the ideal nutrient for the newborn, but unfortunately also a route of excretion for some toxic substances including lead . Lead reach into breast milk through passive transfer, this depending on three major characteristics; polarization of the chemical at body pH, lipid solubility and molecular weight ( 13 , 4 ). The daily permissible intake estimated by WHO, 1972 for infant is 5 µg/kg/day of breast milk (11).

The aim of present study was to confirm a correlation between the lead levels in drinking water (surface and groundwater) of Dakahlyia governorate and that of breast milk of lactating mothers living in that area.

Subjects And Methods

Drinking water samples

Fifty-two drinking tap water samples (surface and groundwater) were collected in Sept.2007 from different districts of Dakahlyia governorate, Table (1), Fig. (1).

Figure 1

Table 1: Localities of drinking tap water samples in Dakahlyia governorate

Figure 2

Breast milk samples

Fifty-two Breast milk samples were collected from lactating mothers joining their babies in governorate hospital of previously mentioned districts, Table (2). A history was taken from the mothers through answering a questionnaire, which included; age, source of drinking water, nature of occupation, and smoking (active or passive exposure).

Figure 3

Table 2: Localities of lactating mothers

Procedure of breast milk sampling

Statistical analysis

Results

Table (3) showed that Lead levels of drinking groundwater samples were ranged from 0.016 to 0.023 mg/l with mean of 0.019 ±0.003 mg/l. Also, lead levels of drinking surface water samples were ranged from 0.011-0.017 mg/l with mean of 0.014 ± 0.002 mg/l.

Figure 4

Table 3: Lead levels (mg/l) in drinking tap water samples

Table (4) showed that there was statistically significant increase in lead levels in drinking ground water compared to surface water (p< 0.001).

Figure 5

Table 4: Mean lead levels in drinking tap water samples

The mean age of mothers drinking surface water was 29.4±5.7 years, while the mean age of mothers drinking groundwater was 26.1±6.2 years, with statistically non significant difference (p = 0.052) as shown in (Table 5).

Figure 6

Table 5: Age of the studied groups

Table (6) showed that there was statistically significant increase in lead levels in breast milk of mothers drinking ground water compared to mothers drinking surface water (p< 0.001).

Figure 7

Table 6: Mean lead levels of mothers' breast milk (mg/l) as regard the type of drinking water

Table (7) showed a positive correlation between lead levels in drinking water and mothers' breast milk , however there was statistically significant increase in the lead levels in breast milk compared to its levels in drinking water in both group (p< 0.001).

Figure 8

Table 7: Comparison between mean lead levels (mg /l) in drinking water and mothers' breast milk as regard the type of drinking water

Table (8) showed a significant increase of lead levels in breast milk of women passively exposed to smoking compared to non exposed one (p< 0.001).

Figure 9

Table 8: Mean lead levels of mothers' breast milk (mg/ l) as regard passive exposure to smoking

Discussion

It is a known fact that intoxication of newborn may be caused by breast feeding with milk containing heavy metals ( 7 , 9 ). In the present work, all investigated water samples were considered suitable for drinking according to EMH (5) where these samples showed lower levels of lead than the permissible limit (0.05) mg/ l but, according to WHO (17) they showed higher levels of lead than the permissible limit (0.01) mg/ l, Table (3).

Overall mean lead level in drinking groundwater showed higher levels than in drinking surface water (Table 4). Levels of lead in drinking water sampled at the source are usually below 0.05 mg/l. However, water taken from taps in homes where lead is present in the plumbing can contain levels up to 1 mg/l (14).

An elevation of lead concentrations in breast milk of mothers drinking groundwater was noticed when compared with that of mothers drinking surface water (Table 6). The higher levels of lead in drinking water and mothers' breast milk of groundwater origin observed in the present work could be attributed to more industrialization, living near high-traffic roads and the potential exposure to automobile exhaust, in addition to the use of lead water pipes lines. Pipe system may still be joined by lead solder and lead lined storage tanks are common in houses (10). The comparison between mean lead levels (mg/l) in drinking water and mothers' breast milk samples showed positive relationship (Table 7).

In this study, all women were non-occupationally exposed to lead. They had no special habits but, twenty five women (48.1%) were exposed passively to smoking i.e. passive smokers. These women showed higher lead contents in their breast milk compared to non exposed women (Table 8). Similar finding was encountered in a study by Kwapulinski et al., (8).

The permissible lead limit established by WHO is 5 µg/kg/day based on 840 ml breast milk for a 5.5 kg infant per day (15). In the present study, calculated daily lead intake in breast milk according to its values was presented, Infant of mothers drinking surface water would ingest (3.81 µ g/kg/day), however infant of mothers drinking groundwater would ingest (5.34 µg/kg/day) which was higher than the permissible value established by WHO. In the study done by Abdel-Latif and El-Kolaly (1), they found that an infant 5.5 kg for woman from Cairo would ingest 6.6 µg/kg/day, while an infant for a woman from other governorates would ingest 4.3 µg/kg/day which are lower than the daily permissible limit.

Conclusion

Lead excretion via breast milk reached high levels among women living in polluted areas and those exposed to passive smoking compared to non exposed women hence suckling infants were getting more lead. Prolonged contact with lead plumbing also increased the lead content in tap water with subsequent increase of lead burden in infant fed formula and infant blood.

Recommendations

1. Specialized multiple stages filters must be used mainly in water stations and also in houses

2. Chemical analyses must be carried-out periodically for the surface and groundwater to ensure the water suitability for drinking purposes (water must be free from lead or within the permissible limit of WHO).

3. Drawing water for drinking after flushed from the tap water by 1-2 minutes.

4. Programmes should be developed to facilitate identification the pollution of lead on the basis of monitoring data.

5. The use of PVC (poly vinyl chloride) pipes and engineering practices to minimize plumb solvency in water treatment and water distribution systems.

6. The abstinence from smoking, improved diet and vitamins supplementation shall play an important role in lowering lead levels and thus preventing lead toxicity in pregnant women and their fetuses.

Acknowledgement