Radiation and Childhood Cancer

correlation between pyrene collected on filter and pyrene collected on XAD (4. On average, we found 1.6 pg/m3 pyrene on filter and 1.9 pg/m3 on XAD; i.e., 46% on filter and 54% on XAD. This is in good agreement with Ny et al. (3). The correlation between pyrene on filter and the sum of pyrene on filter and pyrene on XAD was 0.69. Since this is less than 1, it is likely that a better correlation between pyrene in air and urinary 1-hydroxypyrene would have been the result of using an XAD backup in our study. The timing of urinary sampling is an important issue. However, it is impossible to select a perfect sampling time for biological monitoring. Even ifyou sample for 8 hr and start at a time point equal to the half-life of 1-hydroxypyrene after the start of work, some of the collected urine will contain 1hydroxypyrene from the previous day's exposure, and day-to-day variation may be significant. Jongeneelen (4) has studied samples collected after and before shift and found a correlation between pyrene in the air and urinary 1-hydroxypyrene both when collected after shift and before the shift the next day. The American Conference of Industrial Hygienists (ACGIH) has established biological exposure indices (BEI) for several organic compounds (but not pyrene) and suggested sampling times. The ACGIH suggested end of shift and prior to next shift as the time when sampling time is critical (5). Compromises have to be made in practical biomonitoring, but for validation of methods, 24-hr sampling of urine may be important. We agree that 1-hydroxypyrene is the main metabolite and that other metabolites are important, but urinary 1-hydroxypyrene is a marker for PAH exposure and does not represent the total exposure. A large proportion of PAHs are excreted in feces. In a recent study of voluntary ingestion and dermal application of pyrene, less than 4.5% (ingestion) and 0.2% (dermal) of the dose was recovered in a 48-hr collection period (6). The study of the influence of genetic factors and lifestyle factors is important in validating biomarkers like urinary 1hydroxypyrene. We are currently conducting such studies. But PAH uptake is also influenced by particle size of the PAH. The new filter cassettes called IOM (7) show that construction of cassette orifice can have a great impact on the fraction samples and may be more important than AD backup,which mostly gives a constant loss that can be corrected for. There is still need for more validation studies of the biomarker 1-hydroxypyrene. To sum up, we would like tO cite from implementation of the BET (5i): "Biological monitoring should be considered complementary to air monitoring. It should be conducted when it offers an advantage over the use of air monitoring alone."