Many Department of Defense (DoD) facilities require rapid, on-site measurements of airborne lead levels to insure worker safety and verify that the Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) of 50 micrograms per cubic meter has not been exceeded. The U.S. Environmental Protection Agency has mandated (40 CFR 50) monitoring at lead-based paint facilities and firing ranges. Current OSHA protocols require Personal Breathing Zone (PBZ) samples to be sent to an off-site laboratory for analysis, resulting in delayed reporting times and high compliance costs. Field demonstrations of the portable AeroLeadTM PBZ Analyzer were conducted at shooting ranges at the Naval Amphibious Base in Little Creek, Virginia and at the Marine Corps Air Ground Combat Center facility in Twentynine Palms, California. The AeroLeadTM analyzer was also tested on aerosol lead samples generated under controlled conditions at the Oak Ridge National Laboratory in Tennessee.
The AeroLeadTM portable lead analyzer automatically samples and measures metal concentrations in ambient air. Air samples are drawn through a sample filter/detector assembly. The airborne lead is then extracted and concentrated into a specially designed aqueous phase consisting of dilute hydrochloric acid and extractants and analyzed voltammetrically. An integrated airflow meter is used to determine air-sample volume, which is combined with the voltammetric data to yield an accurate airborne lead concentration. The instrument then automatically resets for the next sample. The analyzer has the capability to automatically measure airborne lead concentrations to below 10 micrograms per cubic meter within a total sampling and analysis time of 15 minutes.
The AeroLeadTM did not meet all of the performance criteria during this program and therefore was not validated. A high degree of variability was observed in performance between the analyzer units at the three standard lead concentrations tested (126-356 micrograms per cubic meter). Inter-instrument variability contributed to an overall precision for all instruments of between 65 and 82 percent. Inter-instrument variability in accuracy (bias) ranged from 29 to 74 percent. Capture efficiency (100 percent) and extraction efficiency (91 percent) were validated under this program.
The AeroLeadTM Analyzer has several advantages including (1) rapid, cost-effective turnaround of analytical results and (2) enhanced health and safety for on-site workers. These features will enable workers to adapt to changes in the ambient lead concentrations during training, cleanup or lead abatement activities, and rapid reoccupancy of a recently abated building. Estimates indicated that costs would have been reduced from $25 to less than $3 per sample, which means that potential DoD-wide savings could exceed $100 million.
The primary source of the inter-instrument variability was traced to response differences between working electrodes. The manufacturer is currently improving working electrode design and manufacturing techniques so that sensitivity/response issues may be resolved. (Project Completed - 2002)