The end phase of any remediation or abatement activity is the clearance process. The clearance process for environmental contaminants verifies if the work area has been returned to pre-loss condition — typically by the process of a visual inspection and sampling. While many of these projects meet the criteria required, many others fail. In this blog we will discuss lead clearance sampling and what to do if your project fails clearance.
Basics of Lead Abatement
Lead based paint was used in residential properties throughout the country until the late 1970s until it was officially banned. Lead abatement is recommended during renovations or removal of material that contains lead based paint. The abatement process can involve a myriad of removal methods, such as the use of solvents or scraping of the lead paint. This is typically done within a contained space with poly sheeting and negative pressure, similar to asbestos containments. Once all of the lead based paint and/or dust is removed, clearance activities will begin. Since lead is heavy metal and it typically settles out of the air faster than other contaminants, air sampling is not done to clear the area. Clearance is achieved by sampling the dust present to see if it meets regulatory compliance.
Basics of Lead Wipe Clearances
Lead clearance is conducted by using a lead wipe, utilizing the NIOSH method 9100. The process begins with donning sterile gloves and using a template or measuring the space that will be sampled and marking the area with masking tape. Standard sizes for templates and sampling range from 100 square centimeters to the more common square foot. The wipe is then removed from its packaging and unfolded. The wipe is then used across the area in specific folded configurations and then placed inside of a vile. The sample is then submitted to an accredited laboratory for analysis. A common method for analysis for lead wipes is flame atomic absorption spectrometry (Flame AAS). This method involves placing the wipes and blanks collected into a solution that includes nitric acid. The solution is then drawn into a flame and its spectra is analyzed by instrument to determine the amount of lead present. The result is calculated based on the lead present and the size of the area wiped. The regulatory limits for lead dust for the Illinois Department of Public Health (IDPH) is 10 micrograms per square foot for floors and 100 micrograms per square foot for any other horizontal surfaces. Fun fact, prior to working at Indoor Science I was a lead analyst at an accredited laboratory.
Why Do Clearances Fail and How Can They Be Fixed?
Lead clearance fails because cleaning was improperly or inadequately conducted. The amount of lead that meets clearance criteria is a very minute quantity and is often not visually seen with the naked eye. In recent years the lead dust limit for floors was 4 times higher than its current standard. This could lead to failures if protocols were not adapted to meet current standards. Once failure has occurred the area must be recleaned until clearance can be met. A method that I often recommend to contractors who fail testing is to perform the HEPA sandwich method which is also used in mold remediation. This method involves sequential cycles of HEPA vacuuming and wet wiping surfaces. Contractors that I have known who have used this process properly have generally passed clearance on the next testing. Any additional costs incurred by failed lead clearances should be handled by the abatement contractor.
Lead clearance testing should be performed by a third party company with no financial ties with the abatement contractor to reduce bias, such as Indoor Science.