Transition of cord blood lead level, 1985-2002, in the Taipei area and its determinants after the cease of leaded gasoline use

Lead has long been of concern for its toxicity, impairment of neurobehavioral and cognitive development, and electrophysiological deficits in children, even at levels less than 10μg/dL. The present study was conducted to elucidate the extent of cord blood lead level decline in the Taipei area from 1985 to 2002 and to explore the factors affecting the cord blood lead level after the cease of leaded gasoline use. In the current study period of 2001-2002, 184 of 1310 newborns delivered in the Taipei Municipal Women and Children Hospital between September 2001 and August 2002 were eligible and randomly selected to participate in this study. Neither of their parents had an occupational lead exposure history. At each delivery, a sample of 5-10mL umbilical cord blood was collected for lead determination by graphite furnace atomic absorption spectrometry. The cord blood lead level of the newborns in the current study period averaged 2.35±1.12μg/dL. Together with the cord blood lead averages of 7.48±2.25 and 3.28±1.52μg/dL obtained from two previous surveys conducted in 1985-1987 and 1990-1992, respectively, the cord blood lead level was significantly decreased (P<0.005). It is estimated that such a reduction in cord blood lead from 7.48 to 2.35μg/dL for each year's cohort of 260,000 newborns in Taiwan might benefit the economics, ranging from US$8.9 billion to US$12.1 billion by improving the worker productivity. For the time period from 1985 to 2002, there were consistent transition patterns among the yearly fluctuations of air lead level, leaded gasoline consumption, lead content in gasoline, estimated lead amount emitted from the consumed leaded gasoline, and average cord blood lead levels of the three respective study periods. Additionally, every 0.1-g/L reduction in lead content in gasoline might lead to a lowering of cord blood lead level by 1.78μg/dL. Furthermore, at low level of around 2μg/dL, a multiple regression analysis demonstrated that economic status was the most influential factor for cord blood lead variation (P=0.0061) while the maternal working month during her pregnancy was retained in the model with borderline effect (P=0.0625). After accounting for the effect of leaded gasoline on the cord blood lead level, future study to differentiate the primary contributors for the low-level cord blood lead variation around 1-2μg/dL is warranted.