News from the Texas Commission on Environmental Quality (TCEQ)

The Toxicology Division of the TCEQ recently (September 2015) updated their publication, “TCEQ Guidelines to Develop Toxicity Factors” (TCEQ Publication RG-442).  This document outlines the procedures used to set Effects Screening Levels (ESLs) and Air Monitoring Comparison Values (AMCVs) in Texas.  This approach supercedes the former default method of setting ESLs, which lacked a true scientific basis.  In the past (for example, when I was with the agency from 1984 to 1991), health-based ESLs were set equal to 1% of the most applicable occupational exposure limit.

ESLs now exist for approximately 5,000 chemicals.  Of those, only 50 or so have been set using the RG-442 methodology.  That leaves a lot of work for the agency to do.  One aspect of the process that might be of interest to you is that the agency will accept data from concerned parties.  Such data is considered in the setting of new ESLs and AMCVs.  Comments are now being requested for two chemicals: diisopropylamine and dibutylamine.  If your company uses either of these two chemicals, it would behoove you to submit any data you think might be to your advantage to the agency for consideration.  Comments on these two chemicals are due March 25, 2016.

Effects Screening Levels are used in TCEQ’s air quality permitting process to evaluate air dispersion modeling’s predicted impacts for air contaminants.  ESLs are based on data concerning health effects, the potential for odors to be a nuisance, and effects on vegetation.  ESLs are not ambient air standards. If predicted airborne levels of a constituent do not exceed the screening level, adverse health or welfare effects are not expected. If predicted ambient levels of constituents in air exceed the screening levels, it does not necessarily indicate a problem but rather triggers a more thorough review.

AMCVs are concentration levels of air contaminants used to evaluate air monitoring data and are set to protect human health and welfare.  Short-term AMCVs are based on data concerning acute health effects, odor potential, and acute vegetation effects, while long-term AMCVs are based on data concerning chronic health or vegetation effects. Similar to the ESL concept, if measured levels of an air contaminant do not exceed its AMCV, no adverse effects are expected.  If the AMCV is exceeded, more study is initiated.

A copy of the new RG-442 document can be downloaded at the agency’s web site.