Comment submitted by W. L. Townsend

Disclaimer: My comments do not in any way represent the position of the Southern Nevada Health District (SNHD). The official position of the SNHD, if any, will be made by the Chief Health Officer, SNHD. My comments are submitted as a concerned citizen focusing on the health and well-being of our children. I am the Project Director, however, of the SNHD Childhood Lead Poisoning Prevention Program (CLPPP). In addition, I am a Certified Industrial Hygienist (CIH) with over 20 years of experience developing and implementing programs to ensure the protection of the health of the workforce from exposure to a vast number of "airborne contaminants," including airborne lead. As you may be aware, the airborne standards that govern the workforce/occupational exposures, are based on an 8-hour day, 40-hour week for a "healthy adult." Public exposures are typically an "order-of-magnitude" or more less than the occupational exposure standard. The current NAAQS for lead, as you know, is 1.5 mcg/m3 averaged, arithmetically, over a 90-day period. Assuming evenly distributed daily (24-hour) exposures, the equivalent value to maintain compliance with the NAAQS is approximately 0.017 mcg/m3. Faced with the problem of trying to identify the plausible sources and routes of childhood lead exposure, I conducted a study to see if "inhalation of airborne lead" was a plausible route and contributed significantly to the blood-lead level (BLL) of lead poisoned or lead exposed children. From a review of the scientific literature, I was able to find a mathematical model relating "air lead level/concentrations" (i.e., ALL) to "blood-lead levels/concentrations" in children less than 6 years of age. The model was described by Hayes, et.al. as follows: ln(BLL) = 0.24*ln(ALL) + 3.17. In my study, I conducted air monitoring in pre-1978 homes of children diagnosed with elevated blood-lead levels. The children's "actual" BLL results as determined by Quest Diagnostic Laboratories compared quite favorably with the "predicted" BLL results obtained using the Hayes, et.al. model. The differences seen between "actual" and "predicted" BLL results were not significant (p = 0.78). Using the Hayes et.al. model, ln(BLL) = 0.24*ln(ALL) + 3.17, and assuming an evenly distributed daily (24-hour) exposure value of 0.017 mcg/m3 to achieve compliance, the predicted BLL is 9 mcg/dL. This predicted BLL is lower than the current CDC "level of concern" (i.e., 10 mcg/dL), but it is still higher than what we would like. Clearance testing: I feel air sampling for airborne lead levels should be part of the clearance testing procedure. The proposed regulation (study used) sites 2 mcg as the limit-of-detection (LOD). I feel this value is too high, unless a huge volume of air is drawn through the filter. Using the Hayes, et.al., model, the LOD should be less than 10-E6 mcg/m3 or even as low as 10-E9 as shown below: ALL BLL mcg (mcg/m3) (mcg/dL) 2 0.154320988 15.20321742 0.01 0.000771605 4.262734729 0.004 0.000308642 3.421233416 0.0004 3.08642E-05 1.968714342 0.0001 7.71605E-06 1.411524131 0.00001 7.71605E-07 0.812247358 0.0000001 7.71605E-09 0.268960378 Finally, I feel it would be prudent to lower the NAAQS from the current level of 1.5 mcg/m3 and establish clearance standards that include monitoring for "airborne lead." This is important when protecting children's health since there is no threshold for lead exposure as it relates to children. Thank you for the opportunity to comment. Should you desire to contact me, I may be reached at 702-759-1295.