A recent scientific panel that evaluated the utility of hair sampling for assessing exposure to chemicals routinely found in the ambient environment concluded that the method is too inconsistent to be relied upon, with the possible exceptions of methylmercury and arsenic (Harkins and Susten 2003).
These studies lend support to the use of a single sample for exposure assessment.
Michigan PBB cohort enrollment data, along with blood samples for exposure biomonitoring that included PBB and PCB, were collected from 1976 1987 by the MDCH.
All of the above studies failed to account for the high variability in BPA exposure across pregnancy, using a single spot urine sample for exposure assessment, and the heterogeneous etiologies of preterm birth (IOM 2006; McElrath et al. 2008).
A major strength is that a population-based birth cohort was followed for > 7 years, and samples for exposure assessment and vaccine antibody assessments were collected at several time points.
Although it is still uncertain if Pb is truly a cause of end-stage renal disease, this first low-level study using prospectively collected samples for exposure assessment shows associations that give reasons for concern.
Knowledge of the variability of HAP concentrations over days, months, and seasons can inform the design of an ideal sampling plan for exposure assessment.
Although third-trimester O3 exposure was positively associated with LBW, we did not observe any significant association between any of the measured pollutants and LBW in our sample for exposures averaged over the entire pregnancy or for exposures during the first and second trimesters.
Several investigations have shown that counter-matching on a correlate of exposure is more efficient than simple random sampling for assessing exposure dose response and gene exposure interactions over a wide range of situations [ 37, 41- 43].
Thus, if blood is to be sampled for determination of arsenic for exposure analysis, careful planning and a consistent sampling strategy should be employed.
