Pacific Steel air quality Manganese Formaldehyde Benzene health risks exposures

BAAQMD Monitoring Data Summary

Health Risks in Dispute!

   

ALSO SEE: BAAQMD Monitoring Data Summary

Mark Chernaik, Science For Citizens (responds to data analysis by BAAQMD)

Subject: Summary and Analysis of West Berkeley Air Monitoring Results (BAAQMD report of 4/19/2009)

With respect to the report "Summary and Analysis of West Berkeley Air Monitoring Results," released by the Bay Area Air Quality Management District on April 14th, 2009:

I collected all of the data for manganese, nickel, formaldehyde, benzene and iron from the U.S. EPA AQS Data Mart.  Please see the attached spreadsheet.  I can confirm that the annual averages reported by Bay Area Air Quality Management District in Table 2 on page 5 of the report are accurate.

My biggest criticism of the report is how it interprets the data with respect to the Hazard Quotient from exposures to manganese.   Table 4 of the report uses a Chronic REL for manganese of 0.09 ug/m3 to derive a Hazard Quotient of 0.411 for the exposure to an annual average concentration of manganese of 0.037 ug/m3.  

However, according to the U.S. EPA: "The Reference Concentration (RfC) for manganese is 0.00005 mg/m3 based on impairment of neurobehavioral function in humans."  http://www.epa.gov/ttn/atw/hlthef/manganes.html   This is equivalent to a concentration of 0.050 micrograms per cubic meter, or 50 nanograms per cubic meter.

If the Bay Area Air Quality Management District had used the U.S. EPA RfC for manganese of 0.050 ug/m3, then it would have derived a Hazard Quotient of 0.74 for the exposure to an annual average concentration of manganese of 0.037 ug/m3, based on the nervous system as the target organ system.  

Two other substances found in ambient air at the Berkeley monitoring station also impact the nervous system: benzene and carbon tetrachloride.  The Hazard Quotient for exposure to these two substances is 0.30 (0.15 for benzene and carbon tetrachloride, respectively).  If you add up all the individual Hazard Quotients for
substances (manganese, benzene and carbon tetrachloride) impacting the nervous system (the same target organ system), then the overall Hazard Index in Berkeley for the nervous system is 1.04.

According to page 3 of the report: "The hazard index is taken as the sum of the hazard quotients for each compound that affects the same target organ system (e.g., respiratory system, nervous system, etc.). A hazard index at or below one indicates that no adverse effects would be anticipated to occur." 

In my view, the Bay Area Air Quality Management District should have derived a Hazard Index of greater than one (1.04) based on annual average exposures to substances in Berkeley that target the nervous system.

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Pacific Steel Casting's West Berkeley toxic air emissions profile 2008 Former US EPA employee and West Berkeley resident Peter Guerrero addressing Pacific Steel Casting's airborne emissions at a community meeting.

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Robert J. Blaisdell, Ph.D., Chief
Exposure Modeling Section
Office of Environmental Health Hazard Assessment

Dear Mr   Chernaik,

Ms. Tracy Barreau from the California Department of Public Health forwarded your email of April 22, 2009 with the subject; “Summary and Analysis of West Berkeley Air Monitoring Results” to me.    Ms. Barreau asked me to address the issues that you raise in your analysis of the Bay Air Quality Management District (BAAQMD) monitoring data conducted over a yearlong period near Pacific Steel.  

It isdifficult to address the public health significance of the 1.04 Hazard Index without discussing the methods my agency uses to come up with Reference Exposure Level (REL) values for chemicals and what the REL values represent.    I also discuss below the reasons why the USEPA RfC value is different from the Office of Environmental Health Hazard (OEHHA) REL.  

My agency, the OEHHA is the lead agency for risk assessment in the state of California.   We develop the chronic Reference Exposure Levels (RELs) that you refer to in your email. The chronic REL values are chemical air concentrations that even sensitive members of the general public can be exposed to for at least a large fraction of a lifetime without adverse health effects. Sensitive members of the
general population include, but are not limited to, pregnant women, children, the elderly and those who are sick.    

It is impossible to determine a concentration or threshold in a general population where health effects would begin to occur from prolonged exposure to a particular chemical because the scientific data are not available.   The REL instead attempts to set a public health protective air concentration at or below which the general population would not experience health effects. It is the intent of our Agency to be as certain as the scientific data allow that the REL number is set at a level that is public health protective.   It is thus likely that in most cases that the REL value is substantially below a level where general population adverse health effects would be expected.          

The OEHHA REL is based on a study where workers inhaled manganese over a number of years
(http://www.oehha.ca.gov/air/hot_spots/2008/AppendixD1_final.pdf#page=170 ). The workers experienced neurological symptoms as a result of manganese exposure that could be measured in tests.    OEHHA used a method employing all of the data from this study to estimate an air concentration where a small percentage of the workers would theoretically be impacted.   We then lowered that air concentration by a factor of 300 to account for human variability (including greater sensitivity of children) and the fact that worker study was less than a lifetime study. The REL value is 0.09 µg/m 3 .The OEHHA REL was approved by an independent scientific peer review panel, Scientific Review Panel on Toxic Air Contaminants, composed of University of California professors from various disciplines in 2008.       

The USEPA RfC was last reviewed in 1993 and is based on the same worker study that OEHHA used for our REL. However, the USEPA applied older methods to the data to come up with an RfC value of 0.05 µg/m 3. The lowest dose where an adverse effect was detected in the worker study was lowered by a factor of 1,000 to account for the variability in the human population, the fact that the air concentration where no adverse effects would have been seen workers was not available, and general insufficiency of data. The OEHHA REL and USEPA are remarkably close given the different methodologies. OEHHA’s methods will sometimes give a lower number than the older methods and sometimes somewhat higher. The federal Agency for Toxic Substances and Disease Registry proposed inhalation Minimal Risk Level (MRL) is 0.30
µg/m 3( http://www.atsdr.cdc.gov/mrls/index.html ). The MRL is a health value with a purpose similar to the RfC and REL.  

You have calculated a hazard quotient for several chemicals based on the measured air concentration at the Bay Area Air Quality Management District (BAAQMD) monitoring site near Pacific Steel, divided by the chronic REL or RfC to obtain a Hazard Quotient (HQ). You then calculated, the HQs for the nervous system and added to give a Hazard Index. Exceeding the HQ or HI indicates that the margin of safety is eroded and that the situation should be examined more carefully. As the annual average air concentration increases above the HI or HQ, the likelihood of health effects in the exposed population also increases. The HI that you
calculated using the USEPA RfC for manganese is 1.04.

Exceeding a HI by a small amount such as 0.04 would not typically be cause for public health alarm because of the magnitude of the safety factors. In this case, as mentioned above, the OEHHA REL for manganese has a total safety factor of 300 and the USEPA RfC has a total safety factor of 1000. As also mentioned above, the Hazard Quotient or Hazard Index of 1.0 is not the air concentration where general population health effects are expected. Exceeding a REL during a 24-hour period monitoring period (within reason) is also not a cause for concern because the chronic REL is designed to be protective against long-term average exposure.       

I hope that my response has addressed the public health significance of the 1.04 Hazard Index that you have calculated using the USEPA RfC for manganese and some of the reasons why a USEPA RfC and an OEHHA REL can differ. The science of risk assessment does have its uncertainties, and limitations and risk assessment also changes as new scientific data become available.  

Robert J. Blaisdell, Ph.D., Chief
Exposure Modeling Section
Office of Environmental Health Hazard Assessment
1515 Clay St, 16th Floor
Oakland, CA 94612

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