California Human Health Screening Levels
The California Department of Toxic Control has developed guidelines for the intrusion of fifteen compounds into human breathing spaces. Depending upon where the sample is collected and the “dilution/diffusion” model being employed, the levels of concern can vary greatly. If the measurement point is inside a structure, the levels of concern are the lowest as compared with samples taken beneath a slab or at greater depths below the surface (i.e., soil gas).
The Problems with CHHSLs Analysis
Difficulties analyzing ambient indoor air samples or soil gas for the 15 CHHSL compounds primarily result from the vast range of concentrations that are of concern and are listed as guidelines. This range literally extends from a concentration of 2.79 X 106 ug/m3 for 1,1,1- Trichloroethane at 5 feet below ground to 0.031 ug/m3 for vinyl chloride in residential indoor air. This is a range of nearly eight orders of magnitude. Even within a single category (e.g., indoor air), the range is five orders of magnitude. Laboratories that wish to make money analyzing at both soil gas and ambient indoor levels have a nearly impossible job of making certain that their analytical systems, sampling apparatus and even the laboratory air is clean enough for the low level work. This usually requires a completely separate facility.
Air One Labs Solution
At Air One Labs we have solved the problems associated with the huge range in concentrations in two ways.
- We are a Dedicated Lab for Low Level Analysis. As noted above, sample analysis at the low levels required to meet the CHHSLs is not compatible with soil gas analysis. As a result we have decided to specialize in just the Low Level projects. Our procedures have been developed to handle indoor air and low level soil gas. Expected higher levels (almost assuredly coming from soil gas) will be referred to another excellent lab which can handle the higher sample concentrations.
- Simultaneous Selected Ion Monitoring/ Full GC/MS scan (SIM/SCAN) Even while we are a dedicated low level laboratory, we must treat a large range of concentrations to accurately analyze the CHHSLs. In order to do so we use the latest analytical hardware and software from Agilent Technologies in the SIM/SCAN mode. This allow us to report the very low level concentrations required for seven of the CHHSLs compounds as well as the slightly higher levels of the remaining eight compounds. It also makes certain that any of the fifty other target compounds in our standard analysis AND any possible unexpected tentatively identified compounds (TICs) will not be overlooked.
We at Air One Labs were fortunate and happy to make the decision to begin a new lab with all new and clean state of the art equipment. We chose to purchase the best available equipment to solve the problems of low level air analysis. In a nutshell, we have solved the above issues through the use of the latest technology.
