Assessment of Children’s Exposure to Surface Methamphetamine Residues in Former Clandestine Methamphetamine Labs, and Identification of a Risk-based Cleanup Standard for Surface Methamphetamine Contamination

Introduction The Natural History of a Clandestine Methamphetamine Lab From its initial establishment through its ultimate re-occupancy, a clandestine methamphetamine lab goes through four phases that vary with the nature of operations, the chemicals present, the exposure pathways, and the potentially exposed populations. The four phases may generally be described as Operational: clandestine methamphetamine synthesis takes place Discovery & Removal: the lab is " busted " (discovered by law enforcement) and bulk chemicals and equipment are removed Remediation & Verification: samples are collected to characterize the distribution of contaminants within the residence, the contaminants are remediated, and samples are collected to verify that residual contaminant levels are below target cleanup standards Re-Occupancy: a new group of residents occupies the residence which housed the former clandestine lab Each phase represents a distinct exposure scenario with different primary contaminants, contaminant sources, exposure pathways and potentially exposed populations. Contaminant classes, sources and potentially exposed populations are summarize in Table 1. During the first two phases, inhalation of airborne contaminants (such as methamphetamine, acidic and corrosive gases, and phosphine) probably represents the greatest hazard. Once the primary sources 1 of airborne contaminants have been physically removed, secondary sources may still remain in the residence. Secondary sources include solvent spills and " soft " media (such as upholstered furniture, drapes, carpet and wallboard) that have absorbed solvent vapors and volatile contaminants during the operational phase of the clandestine laboratory. Re-release (or " off-gassing ") of volatile chemicals that have been absorbed into soft media appears to represent the primary inhalation hazard during cleanup and verification activities. For reasons discussed in the following section (" Timeline for Remediation of a Clandestine Methamphetamine Lab "), we assume that airborne contaminants have largely dissipated by the time the residence is ready for re-occupancy. Thus, as the laboratory progresses through these four phases, the significance of inhalation as a pathway of exposure declines markedly. Non-volatile compounds, such as the hydrochloride salt of methamphetamine, represent another general class of contaminants encountered at clandestine labs. Methamphetamine has been detected on interior surfaces at former labs and appears to be persistent (Martyny et al., 2004). Pathways of exposure to these compounds include dermal absorption following skin contact with contaminated surfaces, and ingestion following skin contact and subsequent hand-to-mouth activities. With few exceptions, remediation efforts at former clandestine labs focus exclusively on methamphetamine 1 Primary sources include reaction vessels, solvents stored in their …