Published in October 2019 Focus on the Environment Newsletter
Revision to standards are sometimes necessary as understanding of risks associated with chemicals changes. As has happened before, lead standards are presently in a state of flux. Blood level targets and model inputs used to develop standards for lead have changed over the past few years. These changes already resulted in a change to standards for lead in dust and will likely lead to new soil standards in the future.
Back in 2000, U.S. EPA announced lead dust standards of 40 micrograms per square foot (ug/ft2) on floors and 250 ug/ft2 on interior windowsills. At the same time, they established soil standards of 400 mg/kg in children’s play areas or 1200 mg/kg for bare soil in the rest of a yard. Soil standards for residential scenarios have remained at 400 mg/kg since then, while commercial/industrial are now generally 800 mg/kg rather than 1200 mg/kg. Construction/excavation scenarios often use the 400 mg/kg standard, rather than 1200 mg/kg. The more stringent construction worker standard surprises many people but does have a basis. My legs have received many hugs from small children over the years when I arrive home at the end of a day. Following days on project sites with dirt and dust collecting on my pants, I have often changed at the office before returning home to prevent my kids from running face first into contaminated soil I’ve been investigating or remediating. There may be as much, or more, risk from youth exposure to construction workers’ clothing as there is to the workers themselves.
In recent years, the CDC has revised their blood lead reference value to 5 micrograms per deciliter (ug/dL) from the previous level of 10 ug/dL. Additionally, U.S. EPA updated model parameters for calculating blood standards. In June 2019, U.S. EPA announced the first standard revisions resulting from these changes. The lead dust standard for floors lowered from 40 ug/ft2 to 10 ug/ft2, and the lead dust standard for windowsills lowered from 250 ug/ft2 to 100 ug/ft2.
Interestingly, the June 2019 revisions to lead dust standards were not accompanied by revisions to soil standards. Because the calculations used to develop the standards use many of the same inputs as are used for lead dust standards, and both sets of standards were announced together in 2000, it was anticipated that new soil standards would be announced at the same time as dust standards. Ohio EPA, with this in mind during their recent VAP rule revisions, initially proposed a soil standard of 220 mg/kg in residential/unrestricted use scenarios (down from 400 mg/kg), 1200 mg/kg in commercial/industrial scenarios (up from 800 mg/kg), and 640 mg/kg in construction/excavation scenarios (up from 400 mg/kg). However, in the absence of a correlating change in soil lead standards from U.S. EPA, Ohio EPA decided not to revise the VAP lead standards at this time.
It is not clear when, or if, U.S. EPA will revisit the lead soil standards. It appears that lead remains on the mind of U.S. EPA, and future changes to the lead soil standards are likely. On October 10, 2019, they announced proposed updates to the groundwater lead and copper rule that would keep the same 15 ug/L MCL but require certain actions and responses by public drinking water systems. It may be that U.S. EPA is taking time to consider possible ramifications on projects and industries before proposing new soil standards. Once that happens, residential/unrestricted standards are likely to be lower, while commercial/industrial standards will likely be higher.
Nate Wanner is a Cox-Colvin Senior Scientist with over 15 years of experience leading and completing environmental projects, in addition to six years as an educator and IT director. He holds a BS in Geology: Water Resources from Ohio University and a Masters in Geographic Information Systems from Penn State University. His areas of expertise include brownfields, underground storage tanks, due diligence and database services. Nate is an Ohio EPA VAP Certified Professional (CP), a Certified Professional Geologist (CPG) with the American Institute of Professional Geologists (AIPG) and is a registered Professional Geologist (PG) in Kentucky.