Limited seasonality effects on blood lead for a small cohort of female adults and childrenq

Many blood lead surveys, especially during the 1970s and 1980s have shown variations of up to 35% in blood lead concentration, with higher values in summer over winter. We have monitored 13 adult females and seven children for periods from 348 to 1337 days as non-pregnant controls in a longitudinal study of mobilization of lead from the maternal skeletal during pregnancy and lactation. Samples of blood, 6-day duplicate diet and environmental samples were analyzed by high-precision thermal ionization mass spectrometry for lead isotope ratios and lead concentrations. There was no statistically significant difference between seasons for blood lead concentrations and dietary intake although there were small differences in the isotopic composition for blood. One explanation for the lack of a seasonal effect in blood lead of our cohort may be the absence of climatic extremes in Sydney. The minimal effects from seasonality observed in this cohort make this an especially useful cohort within which to study effects that could be obscured by seasonal factors.