ABSTRACT
Brain development starts early during pregnancy in a process that occurs in a chain of developmental events. Exposure to chemicals especially during critical and sensitive periods of developmental period can lead to a myriad of health consequences that can manifest across individuals’ lifespan and potentially be transmitted to future generations. Evidence has shown that one out of every six children has developmental disabilities and many of them are neurodevelopmental disorders such as learning disabilities, dyslexia, attention deficits, hyperactivity disorder and autism. It is of public health importance to assess the contributions of crude oil exploration and other environmental pollutants in Delta State, a crude oil producing state. The aim of this study was to evaluate the possible effect of environment toxicants on the levels of thyroid hormones, biomarkers of apoptosis and polycyclic aromatic hydrocarbons and some essential elements among exposed pregnant women and neonates and to assess their impact on cognitive development of prenatally exposed neonates. This is a case-control/longitudinal study of adult pregnant women in their third trimester living permanently in Warri south local Government area where there is crude oil exploration and Asaba town where there is no crude oil exploration. A total of 55 apparently healthy pregnant women residing in crude oil exploration area and 33 apparently healthy pregnant women residing in non-crude oil exploration area (controls) were recruited for the study. Ethical approval was sought and obtained from the Ethics and Research Committee of the Central Hospital, Warri, Delta State and individuals who participated in this study gave informed consent to participate in the study. About 8mL of blood was collected from each woman and 3mL was dispensed into EDTA container and mixed, while 5mL was emptied into a plain container. The specimen in plain container was allowed to clot at room temperature and was centrifuged after clot retraction. The serum was separated into a new plain container and stored at -80oC until analysis was done. Also immediately after delivery, the umblical cord was clamped at both ends and cut and 10mL of cord blood was collected from the umbilical vein and 5ml delivered into EDTA and plain containers each and labeled. The serum was separated and stored at -80oC until analyzed. Blood lead (Pb), cadmium (Cd), copper(Cu), zinc (Zn), magnesium(Mg), and arsenic(As) were assayed using Atomic Absorption Spectrophotometer. Serum triiodothyronine (T3), thyroxine (T4), thyroid stimulating hormone (TSH), human Factor-related Apoptosis (FasL) and Benzo(a)pyrene were determined using Enzyme linked Immunosorbent assay technique while full blood count was done using Haematology analyzer. The cognitive function test was assessed using Fagan test of infant intelligence. The data were analyzed using statistical software SPSS version 20.0. Continuous data was analyzed using chi-square, unpaired Student’s-test and one way analysis of variance (ANOVA), while unadjusted Odd ratio was used to determine the association between measured variables and intelligence quotient. A p-value ≤0.05 was considered statistical significant. Maternal blood concentrations of Pb (0.08±0.01), Cd (0.29±0.03),As (0.88±0.06),FasL ((31.40±1.92) and BPDE (1723.57±51.06) were significantly higher (p<0.05) among exposed mothers than non exposed mothers. Serum TSH was significantly higher (p=0.036) among the exposed pregnant women (2.81±0.12) than non exposed pregnant women (2.45±0.16), while serum T3 was significantly lower (p<0.001) among exposed pregnant women (6.97±0.20) than non exposed pregnant women (9.39±0.31). The T3/T4 ratio was significantly lower (0.60±0.02) among exposed women than non-exposed women (0.78±0.001)(p<0.001). Umbilical cord blood levels of TSH and T3/T4 ratio were lower while T4 was higher among prenatally exposed infants than non exposed neonates. Some 30/55(54.5%) and 35/55(63.6%) of prenatally exposed infants had low Fagan test of infant intelligence and low APGAR score than 12/33(36.4%) and 16/33(48.5%) among non exposed infants and mothers. Alterations in thyroid gland function were associated with Fagan test of infant intelligence, blood concentrations of lead, cadmium and arsenic. The data from this study indicated that pregnant women residing in crude oil bearing communities and their newborn infants may be significantly affected by crude oil and associated environmental pollutants.
