The DTSC ordered Exide to cease operation on April 24, 2013 claiming that:
16.1 In a letter dated March 1,2013, the SCAQMD advised Exide that the HRA submitted by Exide in January, 2013 indicates the Facility poses a maximum individual cancer risk (MICR) of 156 in one million for an offsite worker receptor about 300 meters northeast of the Facility (primarily arsenic).In addition to compromised stormwater piping that Exide self-reported, the HRA values for cancer and non-cancer risk were also used by the DTSC to claim the need immediately shut down operations on the grounds that these two situations met the 25186.2 conditions for DTSC action "necessary to prevent or mitigate an imminent and substantial danger to the public health or safety or the environment."
Assuming that fixing the stormwater pipes corrects and mitigates that issue, does Exide pose a "maximum individual cancer risk" now or at the time of the DTSC notice to cease?
Looking at Exide's HRA:
You will notice that arsenic is the primary contributor to the risk number that was quantified. In the RRP, Exide states:
Analysis of the HRA results and concurrent research determined that approximately 90 percent of the above-tabulated risks were due to emissions of arsenic from the Hard Lead Ventilation System stack and that the source of that arsenic was the “leakage” of blast furnace process exhaust from its primary ventilation system into hooding served by the Hard Lead Ventilation System.So if both Exide and the DTSC conclude that arsenic is the chemical of concern for the risk, eliminating or reducing the amount of arsenic put into the air would reduce that risk. Exide made some modifications to their equipment and went back into the original numbers and recalculated the theoretical risk:
Promptly after AQMD approval of the HRA on March 1, 2013, Exide designed an isolation door on the charge chute to the facility’s blast furnace to minimize the potential for blast furnace process exhaust gases to be drawn into the hooding served by the Hard Lead Ventilation System. This door system was permitted on March 28, 2013, and became operational on April 4, 2013. This door remains closed except to open briefly when charge material is actually being added to the furnace, only a small percentage of the time. (1)What if instead of calculating a theoretical risk we could agree on something a little bit more quantitative and easier to understand. Let's makes some assumptions and hold them as true.
- Exide should only be held accountable for the risk they pose over background. That is, if you take Exide out of the equation and there is no difference in the amount of arsenic in the air, then the same risk is still present. Exide is responsible for what they put in over that baseline.
- We will assume that the cancer potency the SCAQMD used for arsenic calculates a risk of 16 in one million for one nanogram per cubic meter of air.
- We will assume that the data collected by SCAQMD and reported in this document accurately reflects the actual amount of arsenic in the air near the Exide Vernon facility.
- We will assume that April 4, 2013 the facility was in operation with the new controls put in place and on April 24, 2013 operations ceased.
- We will assume that "the last week of June" is the 24th of June to indicate when Exide resumed operations.
- April 4 to April 23 (new controls in place)
- April 24 to June 23 (Exide not in operation - background)
- June 24 to September 30th (Exide in operation last date for data provided)
I'll attach at the bottom of this post a gif of the spreadsheet I used to show the numbers that went into calculating these three time frames. Here is what I came up with:
Based on where these monitors are placed...:
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| SCAQMD |
According to SCAQMD's graph:
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| Source |
Based on California's 2003 "Air Toxics Hot Spots Program Risk Assessment Guidelines" the formula for calculating excess cancer risk look like this:
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| Appendix I - 4 |
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| Appendix I - 2 |
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| Appendix I - 3 |
...I replaced 0,0015 micrograms with 0.0001 micrograms (1 nanogram). The inhalation dose, based on 1 ng/m3 equals 3.8 x 10-8 mg/kg-day
To calculate the cancer risk per million, I replaced the Inhalation dose in the following example with the one calculated based on 1 ng/m3:
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| Appendix I-4 |
So what does all this mean?
The DTSC gave an immediate cease operation order to Exide based on "imminent and substantial" harm to the public, claiming that:
Based on the Health Risk Assessment submitted to the SCAOMD, DTSC has determined that the Facility is operating its furnaces and its air pollution devices in a manner that is not sufficiently protective of human health and the environment, impacting as many as 110,000 residents in a large geographical area...The HRA is a theoretical exposure calculated by Exide. The graph SCAQMD put together represents actual concentrations of arsenic in the air. Before the order to cease operations was given by DTSC the SCAQMD had been collecting arsenic concentrations in the air in and around the Exide facility.
The SCAQMD calculated the highest monthly average of 3.33 ng/m3 from the off-site ATSF in May of 2012. Assuming that all of that arsenic came from Exide - less the background I calculated (0.75) - this would give us a concentration of 2.58 ng/m3.
2.58 ng/m3 exposure equals a dose of 9.7 x 10-7. With that dose, using the California HotSpot calculations, the excess cancer risk would be 11.67 in one million.
Would the highest amount calculated - before the modifications were made - be considered "imminent and substantial"? That depends on how those two terms are defined. Here is what the SCAQMD defines as "significant" in their Rule 1402:
Under the rule for air emissions, a cancer risk of 11.67 per one million would equal a risk of 0.11 per one hundred million and would not be considered "significant."
All of this information was available to the DTSC. Heck if I can find it just using Google and a team of me, myself, and I, so could the DTSC.
Next Post: If they only had a RCRA permit...Part 8
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