Letter re: EPA/DEP WTC dust cleanup at 114 Liberty Street,

NYC 9/11 Public Portal Document

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EPA was obligated to address any analytical problems when it could not detect silica at the levels of concern by additional abatement, just as it does when the filters are overloaded after asbestos tests.

NIOSH silica standards also exceeded after EPA cleanings EPA has never addressed silica benchmarks prior to 9/11. After the WTC, EPA evaluated the supporting documents for the recommended occupational exposure limit for silica developed by the National Institute for Occupational Safety and Health (NIOSH). EPA concluded there should be an added a margin of safety over the NIOSH standard to protect against the longer exposure periods and the exposures of more vulnerable populations such as children:’® Developing Benchmark Levels Based on Occupational Health Standards For contaminants that lacked environmental toxicity criteria from sources listed in Section 3.2, occupational standards served as the starting point for benchmark development. Additional safety factors were added to account for higher exposure and greater sensitivity within the general population. The health-based benchmarks for fibrous glass and crystalline silica in indoor air were developed in this manner.

Silica. No threshold has been established and it is possible health effects occur below the NlOSHRELof50pg/m\

This NIOSH Recommended Exposure Limit (REL) of 50 pg/m^ assumes a limited workplace exposure time of only 40 hours per week, with no significant exposures during non-working hours. It also assumes workers do not remain employed in silica-contaminated industries for the whole of their lifetime. If the same NIOSH standard of 50 pg/m^ were averaged out for the entire week, the standard would be 12 pg/m^.

At 114 Liberty, the detection limit was 11 pg/m^. This level is essentially the same as the NIOSH standard of 12 pg/m’ for a whole-week exposure. Thus, even when EPA could not detect silica at 114 Liberty, it could not say that the level was below the NIOSH standard designed for healthy adults, much less EPA’s desired health benchmark of 1 pg/m^.

This EPA standard of 1 pg/m’ does not take into account the carcinogenicity of silica. As discussed later, the old 1974 NIOSH standard of 50 pg/m^ was developed long before it was established that silica was a known human carcinogen, causing lung cancer. NIOSH itself is now saying that its old standard of 50 pg/m^ may not even protect against silicosis, not even addressing the carcinogenicity issue.

Most importantly, for 4 of the 11 tests at 114 Liberty, silica levels were found to be 17.2, 19.6, 22.1, and 22.1 pg/m’. These levels are nearly two times the NIOSH week-long standard of 12 pg/m". Levels this high at 114 Liberty are clearly dangerous.

NYC-VVTC_000154987