1 

# Ferroalloys Production NESHAP: 

# URE for Nickel Compounds

Points for Discussion


# March 9, 20122



# Overview

• NiPERA is the human and environmental health scientific research arm of the Nickel Institute, an association of worldwide nickel producing companies representing ~90 percent of global nickel production.

• Our concern is that the URE value EPA used for nickel compounds in this rulemaking is not well

- founded. It should be corrected, so that a more accurate and scientifically sound value is used.

• Cancer risk from nickel emissions was not the basis for finding the residual risk in Ferroalloys Production (FP) to be unacceptable; the HI for manganese was the driver. So correcting the URE for nickel would not change the finding of unacceptable residual risk. But it would provide a more appropriate basis for estimating nickel

- related cancer risks here and in future proceedings.3 

# Assumptions for Deriving URE

• For purposes of deriving a URE to apply to the mix of nickel compounds present in FP emissions, we are prepared to make the following assumptions, even though we question several of these points:

– All nickel compounds are potentially carcinogenic to some extent, and a single URE can be applied to all of them as a group (total nickel) for purposes of estimating cancer risk.

– URE values derived from occupational studies of nickel refineries processing sulfidic ores (where nickel subsulfide is a major component of emissions) can be used to assess cancer risks associated with environmental exposures from sources (like Ferroalloys Production) where nickel subsulfide is a minor component of nickel emissions (if it present at all). But the focus should be on refinery studies where Ni 3 S 2 was relatively less prominent.

– A linearized, non

- threshold exposure

- response model can be used to assess cancer risk from low

- level environmental exposures to nickel.4



# EPA’s Approach

• In its residual risk assessment, EPA used the IRIS URE value for nickel subsulfide ( i.e., 4.8 x 10

- 4 

# per μg/m 3 

# ) and applied it to 

# the maximum estimated exposure concentration of total nickel ( i.e , all nickel species combined) from emissions at 

# Ferroalloys Production facilities.

• There are logical problems with this 

# approach.5



# Logic Problems

• While it was a major component of total nickel in the 4 nickel refinery studies on which the IRIS URE value for nickel subsulfide is based, Ni 3 S 2 is at most a minor component of total nickel in emissions from Ferroalloys Production.

• Even in the 4 nickel refinery studies from which the IRIS URE value was derived, EPA did not find an increased cancer risk of 4.8 x 10

- 4 per μg/m 3 . Nor has any other regulatory body.

• What EPA found was an upper bound estimate URE of 2.4 x 10

- 4 per μg/m 3 for workers exposed to the mix of nickel compounds present in the 4 nickel refineries. It then arbitrarily doubled that value to derive a presumptive URE for Ni 3 S 2 of 4.8 x 10

- 4 per μg/m 3 based on the assumption that Ni 3 S 2 constituted 50% of the nickel species to which the refinery workers were exposed but was responsible for 100% of the cancer risk

– with the other nickel compounds having no carcinogenic effect.6 

# Logic Problems (continued)

• If EPA now chooses to assume that all nickel compounds are carcinogenic

– so that they all presumably contributed to the increased cancer risk seen in the refinery studies

– it would not be logical to apply to total nickel emissions from FP facilities the artificially doubled URE that EPA constructed for Ni 3 S 2 at a time when it assumed that Ni 3 S 2 alone was responsible for the cancers seen in the refinery cohorts.

• Surely, the mix of nickel compounds present in emissions from Ferroalloys Production (where Ni 3 S 2 is a minor component at best) does not have a higher carcinogenic potency than the mix of nickel compounds present at refineries processing sulfide nickel matte (where Ni 3 S 2 was a major component of total nickel).

– Yet, in its residual risk assessment, EPA assumes that total nickel in FP emissions has twice the carcinogenic potency as total nickel in the refinery studies (4.8 x 10

- 2 versus 2.4 x 10

- 2 ). That cannot be the case.

– Rather, the opposite clearly is the case

– i.e. , the mix of nickel compounds present at sulfide nickel matte refineries is more carcinogenic than the mix of nickel compounds in FP emissions. So a URE greater than 2.4 x 10

- 2 cannot logically be justified even if EPA is determined to stick with outdated IRIS values.7 

# EPA Should Use the TCEQ’s URE for Nickel Compounds

• The IRIS value for exposure to a mix of nickel compounds

– 2.4 x 10

- 4

– is more than a quarter century old. A more updated URE is now available and should be used instead.

• Just recently, the Texas CEQ calculated a URE value for nickel compounds in a manner consistent with EPA guidelines and utilizing a five

- person peer review process (overseen by TERA) that is even more elaborate than the one used by EPA. A second peer review took place just recently when the authors of the TCEQ Nickel Documentation published a journal article based on their work in developing the URE.

• The URE values developed by the TCEQ are 1.6 x 10

- 4 per μg/m 3 based on a comparison to overall U.S. mortality and survival rates and 1.7 x 10

- 4 per μg/m 3 based on a comparison to Texas

- specific mortality and survival rates.8 

# TCEQ URE (continued)

• The TCEQ’s URE value has a sounder scientific grounding than EPA’s IRIS value for a number of

reasons:

– In developing URE values, the TCEQ corrected certain methodology/calculation errors that EPA had made.

– The TCEQ performed more refined and sophisticated modeling than EPA did in 1985.

– The TCEQ used additional and updated data from the last 25 years that were not available to EPA in 1985.

– The TCEQ emphasized refinery studies where the mix of nickel compounds more closely matches the mix of nickel compounds in FP emissions and in ambient air generally.

– The TCEQ’s work has undergone two rounds of peer review that, in combination, must certainly have been as searching and careful as the peer review to which EPA’s risk assessment was subjected in 1985.9 

# TCEQ URE (continued)

• In recognition of the foregoing points, peer reviewers selected by EPA recently endorsed use of the TCEQ URE values to assess cancer risks associated with emissions of nickel compounds to the ambient air.

• As EPA pointed out, “two reviewers suggested using the URE derived by the TCEQ for all Ni compounds as a group, rather than the one derived by the Integrated Risk 

### Information System (IRIS, 1991) specifically for Ni subsulfide. The third reviewer did not comment on an alternative approach.” 77 Fed. Reg. at 9318 (Feb. 16, 2012).10 

# The TCEQ URE Value Is Conservative

• The TCEQ’s URE value was derived using a linear, non

- threshold multiplicative relative risk model as a conservative default assumption.

– But both mechanistic data and results of epidemiological and animal studies indicate that nickel

- related carcinogenicity has an actual or practical threshold, a point recently accepted by the EU’s Scientific Committee on Occupational Exposure Limits.

• The TCEQ’s URE value assumes all nickel compounds are carcinogenic and that a single URE (derived from studies of workers whose nickel exposures contained a significant Ni 3 S 2 component) can be applied to total nickel compounds as a group.

– But it is widely accepted that different nickel compounds have different carcinogenic potential and potencies

– with nickel subsulfide being the most potent.

– A recent paper by B. Conard & S. Seilkop calculates that the carcinogenic potency of nickel subsulfide is at least 5.6 times as great as that of nickel oxide.11 

# TCEQ Conservatism (continued)

• The TCEQ’s URE value is based on studies of sulfide nickel matte refinery workers for whom nickel subsulfide constituted a high percentage of total nickel exposure (50% by EPA’s somewhat arbitrary estimate; 82% by a more careful analysis cited in a recent paper by B. Conard & S. Seilkop).

– By contrast, nickel subsulfide is no more than a minor component of total nickel emissions from FP facilities, if it is present at all. For example, a 2009 paper by D. Sivulka & S. Seilkop calculated that occupational nickel exposures at a high nickel alloy manufacturing facility in the U.S. were 85% oxidic nickel and 7% metallic nickel, with essentially no sulfidic nickel being present.

– And the TCEQ itself cautioned that there is a significant difference in nickel subsulfide exposure between the cohort workers used to derive the URE and environmental exposures of the general population, thus driving its URE to overestimate risks.12



# Conclusion

• The URE value derived by the TCEQ based on overall U.S. mortality and survival rates (1.6 x 10

- 4 

### per μg/m 3 

### ) should be used in the residual risk assessment for the Ferroalloys Production NESHAP and in other instances where EPA assesses respiratory cancer risk associated with exposure to nickel compounds in the ambient air.

• This change would not alter EPA’s tentative finding that 

### residual risk under the Ferroalloys Production MACT scenario is unacceptable. But it would correct the problem in EPA’s current approach and would ensure that EPA’s nickel risk assessment is based on the latest 

### available sound science.