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Higher blood lead levels in rural than urban pregnant women in Eastern Nigeria
  1. Chinwendu Onyekachi Njoku1,
  2. Orish Ebere Orisakwe2
  1. 1Department of Medical Lab Science, Faculty of Science, Rivers State University of Science and Technology Port Harcourt Rivers State Nigeria, Port Harcourt, Nigeria
  2. 2Toxicology Unit, Faculty of Pharmacy University of Port Harcourt Rivers State Nigeria, Port Harcourt, Nigeria
  1. Correspondence to Professor Orish Ebere Orisakwe, Toxicology Unit, Faculty of Pharmacy University of Port Harcourt Rivers State Nigeria, Port Harcourt, Nigeria; eorish{at}

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While blood lead levels (BLLs) in many western countries have progressively declined over the years, in Nigeria, high BLLs continue to be documented not only in exposed workers but also in ‘unexposed’ subjects.1 Lead is an environmental toxin that is capable of causing numerous acute and chronic illnesses. Pregnant women with elevated BLLs transfer lead to the fetus since blood-borne lead crosses the placenta. Through a consideration of the joint associations of maternal BLLs, demographics, obstetrics variables and plasma enzymes levels, this study has attempted to provide data required for crafting effective public health information with respect to prenatal lead exposure in Eastern Nigeria. This work has examined the maternal BLL and evaluated the differences across socio-demographic subgroups/obstetrics variables and plasma enzymes levels. About 90 pregnant women attending Federal Medical Center, Owerri, Imo State, Nigeria participated in this study after informed consent. BLL was investigated using Atomic Absorption Spectrophotometer.

The mean BLL of subjects in rural and suburban settlements (135±160 and 128±135 µg/dl respectively) were higher than those in urban settlements (77±100 µg/dl) table 1. Lead was detected in 86.7% women in this study. The BLL ranged from 0.5–448 μg/dl and 78.9% had BLL greater than 10 μg/dl. The total mean BLL was 99±123 μg/dl. We report here higher BLLs in rural than urban pregnant women in Eastern Nigeria. Major adult exposure includes food, which is believed to account for over 60% of blood levels; air inhalation accounts for nearly 30% while water is of 10%.2 Approximately 5–10% of ingested inorganic lead is absorbed but majority is excreted in the urine. Lead absorption increases with diets rich in fat and low in calcium, magnesium, iron, zinc and copper.3 Since diet of most Nigerian families of low socioeconomic status has the above characteristics, it can partly explain high mean BLL in our cohort. In an unpublished study by Orisakwe and coworkers, the estimated lead intake for rice and cassava based meals (staple foods) in Nigeria were 4.31 and 19.53 g/kg respectively. Food may contribute to the body burden of lead in Nigeria. Among adults, the potential implications of low-level lead exposure are most relevant to women of child-bearing age, as lead is harmful to developing nervous systems of fetuses and children and passes through the placenta and breast milk.4

Table 1

Blood lead levels in pregnant women

Given the high BLL of mothers in this study, it is therefore possible that the pregnant women living in Imo State, Nigeria could be suffering from subclinical lead poisoning. Although levels between 10 µg/dl and 30 µg/dl may produce no clinical symptoms in the mother, they pose significant risk to the fetus.5 Given the high BLL of mothers in this study, pregnant women living in the Niger Delta may be suffering from subclinical lead poisoning. This suggests that the Nigerian infants nursed by the mothers with high body burden of lead may be at risk of neurological damage and impaired growth and development.