1

A. What are the results and proposed decisions for the

Chromium Electroplating source categories? 

1. Overview of the source categories and MACT Standard.

 National Emission Standards for Chromium Emissions from 

Hard and Decorative Chromium Electroplating and Chromium 

Anodizing Tanks (Chromium Electroplating MACT standards) were 

promulgated on January 25, 1995 (60 FR 4963) and codified at 40 

CFR part 63, subpart N. The Chromium Electroplating MACT 

standards regulate emissions of chromium compounds from three 

related source categories: hard chromium electroplating, 

decorative chromium electroplating, and chromium anodizing. 

Within these source categories, the MACT standards apply to all 

plants, both major and area sources, regardless of size. 

The Hard Chromium Electroplating source category consists 

of facilities that plate base metals with a relatively thick 

layer of chromium using an electrolytic process. Hard chromium 

electroplating provides a finish that is resistant to wear, 

abrasion, heat, and corrosion. These facilities plate large 

cylinders and industrial rolls used in construction equipment 

and printing presses, hydraulic cylinders and rods, zinc die 

castings, plastic molds, engine components, and marine hardware. 

The Decorative Chromium Electroplating source category 

consists of facilities that plate base materials such as brass, 

steel, aluminum, or plastic with layers of copper and nickel, 
2

followed by a relatively thin layer of chromium to provide a 

bright, tarnish- and wear-resistant surface. Decorative 

chromium electroplating is used for items such as automotive 

trim, metal furniture, bicycles, hand tools, and plumbing 

fixtures. 

The Chromium Anodizing source category consists of 

facilities that use chromic acid to form an oxide layer on 

aluminum to provide resistance to corrosion. The chromium 

anodizing process is used to coat aircraft parts (such as wings 

and landing gears) as well as architectural structures that are 

subject to high stress and corrosive conditions. 

The HAP emission sources subject to the Chromium 

Electroplating NESHAP are the tanks in which the chromium 

deposition takes place. For hard chromium and decorative 

chromium electroplating facilities, the emission sources are 

electroplating tanks. For the Chromium Anodizing source 

category, the emission sources are anodizing tanks. 

The primary emission controls used by the facilities in 

these source categories include packed bed scrubbers, mesh pad 

mist eliminators, composite mesh pad (CMP) systems, high 

efficiency particulate air (HEPA) filters, and wetting 

agent/fume suppressants (WAFS). Most decorative chromium 

electroplating plants comply with the MACT standards by using 

WAFS in the tank bath to control surface tension, which in turn 
3

reduces emissions. Some plants use a combination of WAFS and 

add-on control to meet the MACT emission limits. If a facility 

controls emissions using an add-on control device, the tank is 

generally equipped with a hood and duct work to exhaust 

emissions through the control device and out the stack. 

However, when WAFS are used as the only means of emission 

control, the tanks often are not equipped with exhaust hoods. 

In such cases, emissions from the tank are fugitive and are 

exhausted to the outside using wall-mounted exhaust fans. 

We estimate that there are approximately 1,770 plants that 

are currently subject to the Chromium Electroplating MACT 

standards. Of these, we estimate that there are 790 hard 

chromium electroplating plants, 740 decorative chromium 

electroplating plants, and 240 chromium anodizing plants. A 

detailed description of how the number of each type of plant was 

estimated can be found in the “Cr Electroplating Estimated 

Number of Plants" document available in the docket for this 

action. Some facilities perform more than one type of chromium 

electroplating or anodizing. For purposes of our estimates, we 

classified facilities as hard chromium, decorative chromium, or 

chromium anodizing based on the primary type of electroplating 

operation performed at the facility. Some chromium 

electroplating facilities electroplate items that are used 

internally in the manufacturing process at the same facility or 
4

within the same company. For example, some large printing 

facilities electroplate their printing rollers in house, and the 

chromium electroplating processes are located at the same site 

as the printing and publishing processes. 

2. What data were used in our risk analyses? 

For the chromium electroplating source categories, we 

compiled a preliminary data set using data in the 2005 NEI. A 

review of the NEI resulted in the identification of data for 122 

chromium electroplating facilities. These data were reviewed 

and the data for eight hard chromium and six decorative chromium 

electroplating plants were revised based on information in the 

facilities’ permits or permit applications. Additional data 

were available for 44 facilities through responses to a CAA 

section 114 information request that was sent to facilities for 

the Plating and Polishing Area Source rule. The data for these 

facilities were added to the NEI data set and, as with the 

original data, represent actual emission levels for these 

chromium electroplating facilities. Most of these facilities 

have low emissions, which are generally less than 2 pounds per 

year. These 166 facilities now included in the NEI comprise 

approximately 9 percent of the estimated 1,770 facilities 

covered by the MACT standards and include 63 hard chromium 

electroplating, 96 decorative chromium electroplating, and 7 

chromium anodizing facilities. This data set of 166 facilities 
5

were modeled to determine the maximum individual cancer risk, 

the population cancer risk, the cancer incidence, and the 

maximum chronic non-cancer risk for the three source categories 

based on actual emissions. The maximum individual cancer risk 

and the maximum chronic non-cancer risk estimated from this data 

set were also compared to the maximum individual cancer risk and 

the maximum chronic non-cancer risk estimated from MACTallowable emissions for the three source categories. 

To address the possibility that the small number of 

facilities included in the 166-facility data set might not be 

fully representative of the source categories and their risks, 

we developed an additional data set. In the development of this 

data set we used “model plants” developed for the original MACT 

standard to represent the individual facilities. For hard and 

decorative chromium electroplating we used three model plants 

(large, medium, and small) that represent average 

characteristics for each of these groups. For each of these 

plant sizes, there is an annual emissions rate (lbs/yr) that is 

derived from the design and operating parameters and is specific 

to the size and type of model plant. For chromium anodizing we 

have two model plants (large and small). The model plants were 

based on data collected during development of the original MACT 

standards from 1988 to 1993 from more than 100 facilities that 

responded to an information collection request for the chromium 
6

electroplating and anodizing industry. Data from site visits 

and other information also were used in developing the model 

plants. A complete description of the model plants developed 

for the MACT standard is provided in the Background Information 

Document for the original MACT standard (Chromium Electroplating 

BID). 

 The basis for this additional data set is 1,629 chromium 

electroplating facilities with known addresses.1

 For about half 

of these facilities the type of electroplating performed is 

known but the size of the facility is not known. For the 

remaining facilities neither the type of chromium electroplating 

process or processes nor the facility size is known. 

 For use in the risk analysis, the limited available data 

were used to divide these facilities into six groups. 

Facilities in three of the six groups were assigned to be hard 

chromium electroplating facilities. Those groups include: hard 

chromium facilities; facilities with combined hard chromium 

operations and other electroplating or anodizing; and facilities 

with unknown processes. Together, these three groups yielded a 

total of 1,219 plants, all of which we modeled as hard chromium 

electroplating facilities. The 1,219 model plants included in 

this data set is substantially higher than the 790 hard chromium 

 

1

 There is some overlap between the 1,629 facilities with known addresses and 

the 166 facilities for which we have emissions data based on the NEI and the 

data collection request. 
7

facilities that we estimate exist in the United States. 

However, because hard chromium facilities have the highest 

emissions among the three source categories, we made these 

selections as a conservative or health-protective assumption. 

The purpose of the residual risk standards under section 112(f) 

is to ensure protection of public health and the environment. 

Thus, we believe it is important to develop a conservative risk 

analysis and err on the side of potential overestimation of risk 

analyses where we are missing data. 

 To represent the decorative chromium electroplating 

facilities, we combined two of the six groups of facilities; 

decorative chromium facilities and facilities that perform both 

decorative chromium and chromium anodizing. This results in 319 

decorative chromium facilities in this data set, which even when 

combined with the 96 decorative chromium electroplating 

facilities in the NEI data set, is less than the 740 facilities 

that we believe exist in the industry. Because we modeled all 

of the unknown electroplating type facilities as the highestemitting hard chromium electroplating facilities, we consider 

this assessment to be conservative even though it appears to 

under-represent decorative chromium facilities. 

 Similarly, the last of the six groups are all known 

chromium anodizing facilities. This group includes 73 

facilities, and when combined with the 7 chromium anodizing 
8

facilities in the NEI data set, still represents only about a 

third of the 240 facilities chromium anodizing facilities. 

Again, we believe this is conservative because those facilities 

not modeled as chromium anodizing plants were modeled as the 

higher emitting hard chromium facilities in the analysis. 

 To estimate the risks for this assessment, we needed to 

establish estimated emissions for each of the electroplating and 

anodizing types. To ensure that we did not underestimate cancer 

risk to the most exposed individual, we originally planned to 

use the large plant emission factors that we had developed for 

the original MACT standard to represent all model plants for 

each type of chromium electroplating processing. In reviewing 

available emissions data, we found that while the large plant 

emission factors adequately represent the average chromium 

emissions from known large decorative chromium electroplating 

and large chromium anodizing facilities, they are not 

representative of the average chromium emissions from large hard 

chromium electroplating facilities. 

 The emission factor for large hard chromium electroplating 

developed as part of the model plant analysis for the original 

MACT standard was 35.3 pounds per year (lbs/yr). However, in 

comparing this emission factor to available emissions data for 

individual facilities we find that this emissions factor is 

unrealistically high and does not represent the average level of 
9

emissions for large facilities as we would expect to see under 

the current MACT standard. As explained more fully in the 

"Model Plant Data Used to Estimate Risk from Chromium 

Electroplating Sources" document available in the docket for 

this action, based on the large model plant design flow rate and 

operating hours, a large hard chromium model plant operating at 

the MACT emission limit of 0.015 milligrams per dry standard 

cubic meter (mg/dscm) would emit a maximum of only 23.6 lbs/yr 

of chromium compounds. Moreover, the available data on actual 

emissions for hard chromium electroplating plants indicate there 

are only 4 plants with annual emissions greater than 10 lbs/yr. 

As a result, we determined that the large size model plant 

emissions factor, as defined for the original MACT standard, is 

not representative of existing large hard chromium 

electroplating facilities on a nationwide basis. However, the 

emission factor associated with a medium size hard chromium 

electroplating model plant (9.26 lbs/yr) falls between the 90th 

percentile (8.04 lbs/yr) and the 95th percentile (11.6 lbs/yr) 

of the available emissions data for hard chromium electroplating 

facilities. Because this emission factor is representative of 

the emissions from large facilities, the emissions factor of 

9.26 lbs/yr was used to represent current large hard chromium 

electroplating facilities. Thus, for purposes of this residual 
10

risk review, we refer to 9.26 lbs/yr as the emissions factor for 

a "large" hard chromium electroplating facility. 

 We believe the approach of using the “large” facility 

emissions factor to represent all facility sizes is reasonable 

to ensure that we did not underestimate maximum individual 

cancer risk. Although we believe that only a small percentage 

of the facilities are large, we recognize that we do not have 

emissions data for approximately 90% of the sources. Thus, by 

assuming all sources are large, we have ensured that we will not 

underestimate the maximum individual risk. 

 For hard chromium electroplating, the model plant emission 

factors for small, medium, and large facilities range from 0.55 

to 9.26 lbs/yr. While we expect only 10 percent of the 

facilities to be large, based on the distribution of model plant 

sizes developed for the MACT standard, we used the emissions 

factor for a large facility (9.26 lbs/yr) for all of the 1,219 

facilities that we considered as hard chromium electroplating 

facilities. Similarly, for decorative chromium electroplating, 

the emission factors for small, medium, and large facilities are 

0.065, 0.27, and 2.65 lbs/yr, respectively, and the large 

facility emissions factor was used in the risk assessment for 

decorative chromium. For the decorative chromium category, we 

estimate that only five percent of the facilities are large, 

based upon the distribution of decorative chromium plants 
11

nationwide when the original NESHAP was developed. Finally, for 

chromium anodizing, the emission factor for small facilities is 

0.036 lbs/yr and for large facilities is 0.44 lbs/yr. The large 

facility emissions factor (0.44 lbs/yr) was used in the 

conservative analysis for all of the anodizing facilities even 

though we estimate that only 25 percent are large. 

Population risk indicators can be greatly overstated when 

highly conservative emission estimates are applied to every 

facility in the source category. Recognizing this fact, we 

performed a supplemental analysis to assess the sensitivity of 

our population risk estimates. Thus, as described further 

below, the supplemental analysis was performed to understand the 

degree to which the risk might be overstated and thus how much 

weight to attach to the conservative analysis, The conservatism 

of this risk assessment is one factor that we consider in 

determining whether the risk is acceptable within the meaning of 

the benzene NESHAP. 

For the supplemental analysis, we assigned unique emission 

factors to each of the 6 groups of facilities in our 1,629 

facility data set. These emission factors were developed to 

better estimate the average emissions for all of the sources 

within each group. The new emission factors are: 

• 2.24 lbs/yr for known hard chromium electroplating 

facilities, 
12

• 0.225 lbs/yr for known decorative chromium 

electroplating facilities, 

• 0.137 lbs/yr for known chromium anodizing facilities, 

• 1.23 lbs/yr for facilities with combinations of hard 

chromium electroplating and either decorative 

electroplating or anodizing, 

• 0.181 lbs/yr for facilities with combinations of 

decorative electroplating and anodizing, and 

• 1.11 lbs/yr for facilities where the type of process 

(electroplating or anodizing) is unknown. 

 A detailed explanation for how these emission factors were 

derived can be found in the "Model Plant Data Used to Estimate 

Risk from Chromium Electroplating Sources" available in the 

docket for this action. These weighted average emission factors 

account for the plant type (hard chromium electroplating, 

decorative chromium electroplating, or chromium anodizing) and 

the distribution of plant sizes (large, medium, or small). For 

example, the average emissions factor for hard chromium 

electroplating (2.24 lbs/yr) is the weighted average of the 

model plant emission factors for large plants (10 percent of 

plants at 9.26 lbs/yr per plant); medium plants (20 percent of 

plants at 4.63 lbs/yr per plant, and small plants (70 percent of 

plants at 0.55 lbs/yr per plant). This distribution of plant 
13

sizes is based on actual data collected during development of 

the original MACT rule. We have no reason to believe the 

distribution of facility sizes has changed significantly since 

then. 

 The uncertainties associated with both the conservative 

analysis and the supplemental analysis include the estimated 

distribution of plant types as well as the facility emissions 

factors. An additional uncertainty associated with these 

analyses is the distribution of plant sizes. Although the types 

of plants used in the both analyses are based on a variety of 

reliable sources, including ICR responses for the Plating and 

Polishing NESHAP, trade association data, data from State 

agencies, and information from websites, we were unable to 

identify the plant type for nearly half of the data set. For 

those plants of unknown type, we used the highest emissions 

factor, which corresponds to a large hard chromium plant, in the 

conservative analysis. For the supplemental analysis, we 

developed an emissions factor using a weighted average across 

all plant types and sizes. For all plants that were modeled, we 

are soliciting additional information on actual and MACTallowable emissions, plant type, and plant size. More 

information about the development of the model plants can be 

found in the “Model Plant Data Used to Estimate Risk from 

Chromium Electroplating Sources” document available in the 
14

docket for this action. 

In all the data sets, chromium compounds account for all 

the HAP emissions from the chromium electroplating and chromium 

anodizing source categories. For the Hard Chromium 

Electroplating source category, in the NEI-based data set, 

chromium VI compounds account for 98 percent of the emissions, 

with chromium III and chromium trioxide compounds comprising the 

remaining HAP. Here, we made the conservative assumption that 

100 percent of the emissions are chromium VI compounds. For the 

Decorative Chromium Electroplating source category, in the NEIbased data set, chromium VI compounds account for 94 percent of 

the emissions, with chromium III and chromium trioxide compounds 

comprising the remaining HAP. Again, we made the conservative 

assumption that 100 percent of the emissions are chromium VI 

compounds. For the Chromium Anodizing source category, in the 

NEI-based data set, chromium VI compounds account for 99 percent 

of the emissions with chromium III compounds comprising the 

remaining HAP. In this case, we also made the conservative 

assumption that 100 percent of the emissions are chromium VI 

compounds. 

3. What are the results of the risk assessments and analyses?

 We conducted an inhalation risk assessment for each of the 

three source categories: Hard Chromium Electroplating, 

Decorative Chromium Electroplating, and Chromium Anodizing. 
15

Also, for each source category, we conducted an assessment of 

facility-wide risk, and performed a demographic analysis of 

population risks. As noted above, we developed two data sets 

for these source categories, one based primarily on NEI data for 

166 sources, and one based on model plant data for 1,629 

sources. 

 The following tables present the combined results from the 

data sets. Table A.1 provides an overall summary of the maximum 

individual inhalation risk assessment results and Table A.2 

provides population risk assessment results for the Hard 

Chromium Electroplating, Decorative Chromium Electroplating, and 

Chromium Anodizing source categories. 

Table A.1. Chromium Electroplating and Anodizing Maximum 

Individual Inhalation Risk Assessment Results

Maximum individual 

cancer risk 

(in 1 million)2

Maximum 

chronic non-cancer 

TOSHI3

Source Category 

Number of 

Facilities 

(NEI/Model 

Plant)1

Actual 

Emissions 

Level 

Allowable 

Emissions 

Level 

Actual 

Emissions 

Level 

Allowable 

Emissions 

Level 

Maximum offsite acute 

non-cancer HQ4

Hard Chromium 

Electroplating 63/1,219 70 90 0.06 0.09 Not appliacable5

Decorative 

Chromium 

Electroplating 

96/337 70 70 0.06 0.06 Not 

appliacable5

Chromium 

Anodizing 7/73 5 5 0.004 0.004 Not appliacable5

1

 Number of facilities evaluated in the risk analysis: the first number refers 

to the NEI data set, and the second number applies to the conservative 

emission estimate. 

2

 Maximum individual excess lifetime cancer risk. 

3

 Maximum target organ specific hazard index (TOSHI). The target organ with 

the highest TOSHI for the Hard Chromium Electroplating, Decorative Chromium 

Electroplating, and Chromium Anodizing source categories is the respiratory 

system. 

4

 The maximum estimated acute exposure concentration was divided by available 

short-term threshold values to develop an array of hazard quotient (HQ) 

values. HQ values shown use the lowest available acute threshold value, 

which in most cases is the REL. When HQ values exceed 1, we also show HQ 

values using the next lowest available acute threshold. See section IV.A. of 

this preamble for explanation of acute threshold values. 
16

5

 NA = not applicable. There are no HAP with acute dose-response benchmark 

values, so no acute hazard quotients were calculated for these source 

categories. See section IV.A of this preamble for an explanation of acute 

threshold values. 

Table A.2. Chromium Electroplating and Anodizing Population Risk 

Inhalation Risk Assessment Results

Conservative 

Assessment 

Population 

at risk 

Supplemental 

Assessment 

Population 

at risk Source 

Category 

Number of 

Facilities 

(NEI/Model 

Plant) ≥ 1-in-1 

million 

≥ 10-in1 

million 

Conservative 

Annual 

cancer 

incidence ≥ 1-in-1 

million 

≥ 10-in1 

million 

Supplemental 

Annual 

cancer 

incidence 

Hard Chromium 

Electroplating 63/1,219 14,200,000 71,000 0.8 360,000 5,100 0.1 

Decorative 

Chromium 

Electroplating 

96/337 390,000 4,000 0.08 30,000 1,300 0.01 

Chromium 

Anodizing 7/73 2,700 0 0.003 540 0 0.001 

 As shown in Table A.1, the results of the inhalation risk 

assessment for the Hard Chromium Electroplating source category 

indicate the maximum lifetime individual cancer risk could be as 

high as 70-in-1 million, based on actual emissions, and as high 

as 90-in-1 million based on allowable emissions. This maximum 

individual cancer risk is based on the highest risk facility out 

of the 63 actual facilities and the 1219 model plants. The 

highest risk facility is one for which we have design and 

operating data, and we believe it is also both the largest and 

highest emitting hard chromium electroplating facility in the 

United States. Thus, we believe this level accurately reflects 

the maximum individual exposure. The maximum chronic non-cancer 

TOSHI value could be 0.06, based on the actual emissions level, 

and up to 0.09 based on allowables. This value is also based on 

known emission levels from the largest facility in the nation. 
17

A non-cancer TOSHI of one or less is not of human health 

concern. 

 The total estimated cancer incidence from hard chromium 

electroplating facilities based on actual emission levels is 0.8 

excess cancer cases per year, or one case in every 1.25 years 

for the conservative assessment. Our risk assessment shows 14.2 

million people exposed to a cancer risk greater than 1-in-1 

million and 71,000 people exposed to a cancer risk of at least 

10-in-1 million. 

 As noted above, we conducted a supplemental analysis to 

determine the weight to give to the conservative risk analysis. 

That supplemental analysis estimates 0.1 excess cancer cases per 

year, or one case in every 10 years. Additionally, it estimates 

a population exposure of 360,000 people at 1-in-1 million cancer 

risk. For a cancer risk of at least 10-in-1 million, the 

population exposed decreases to 5,100. 

 Based on the NEI data set for the decorative chromium 

electroplating source category, the maximum lifetime individual 

cancer risk could be as high as 70-in-1 million, and the maximum 

chronic non-cancer TOSHI value could be up to 0.06, based on the 

actual emissions level.2

 We do not believe the maximum lifetime 

individual cancer risk and the maximum chronic non-cancer TOSHI 

 

2

 There is uncertainty regarding the operating status of the facility 

associated with the maximum lifetime individual cancer risk. Prior to any 

final rulemaking action, we will investigate this situation and revise the 

risk analysis and results accordingly. 
18

value would be any higher than this based on allowable 

emissions. The total estimated population risks from the 

conservative risk assessment of the decorative chromium 

electroplating facilities based on actual emission levels is 

390,000 people exposed to a cancer risk greater than 1-in-1 

million and 0.08 excess cancer cases per year, or one case in 

every 12 years.3

 

 Based on the NEI data set for the chromium anodizing source 

category, the maximum lifetime individual cancer risk could be 

as high as 5-in-1 million and the maximum chronic non-cancer 

TOSHI value could be up to 0.004, based on the actual emissions 

level. The total estimated population risks from the 

conservative assessment of the chromium anodizing facilities 

based on actual emission levels is 2,700 people exposed to a 

cancer risk greater than 1-in-1 million and 0.003 excess cancer 

cases per year, or one case in every 333 years.4

 

 

3

 Based on our conservative risk assessment, we believe the risks are low and 

as explained further below are proposing that the risks are acceptable for 

the decorative chromium source category. Although we did not need to 

consider the supplemental analysis that we conducted for decorative chromium 

to help guide our conclusion about the uncertainty of the risk assessment 

results, we note that the supplemental assessment shows 30,000 people exposed 

to a cancer risk greater than 1-in-1 million and 0.01 excess cancer cases per 

year, or one case in every 100 years. 

4 Based on our conservative risk assessment, we believe the risks are low and 

as explained further below are proposing that the risks are acceptable for 

the chromium anodizing source category. Although we did not need to consider 

the supplemental analysis that we conducted for chromium anodizing to help 

guide our conclusion about the uncertainty of the risk assessment results, we 

note that the supplemental assessment shows 540 people exposed to a cancer 

risk greater than 1-in-1 million and 0.001 excess cancer cases per year, or 

one case in every 1000 years. 
19

 Also, as there were no reported emissions of PB–HAP for 

these three source categories, we do not expect potential for 

human health multipathway risks or adverse environmental 

impacts. 

 Our analyses of potential differences between actual 

emission levels and emissions allowable under the MACT standards 

are based on emissions test data from specific facilities. A 

comparison of these test results to allowable emissions at these 

facilities indicates that the ratio of MACT-allowable to actual 

emissions varies considerably from facility to facility. As a 

result, a uniform factor was not available to apply to all 

facilities. However, for the Hard Chromium Electroplating 

source category, we did evaluate the facility that was modeled 

as having the highest maximum individual lifetime cancer risk 

(70-in-1 million) based on actual emissions. Our analysis 

indicates that this facility, if operated at the allowable 

emissions limit, could have a maximum individual lifetime cancer 

risk as high as 90-in-1 million. Furthermore, the available 

data indicate that no other hard chromium electroplating 

facility would have a cancer risk that high if operated at the 

allowable emissions limit. 

 For the Decorative Chromium Electroplating source category, 

we performed a similar analysis of the available data and 

concluded that the maximum individual lifetime cancer risk would 
20

not exceed 70-in-1 million for any facility that operated at the 

allowable emissions limit. As stated earlier, because most 

chromium anodizing facilities use WAFS, we believe actual 

emissions are essentially the same as allowable emissions. 

Thus, we believe that the MIR based on allowable emissions would 

be the same as that based on actual emissions, i.e., 5-in-a 

million. 

 Table A.3 displays the results of the facility-wide risk 

assessment for actual emissions of all sources at the facility 

as reported in the NEI. We did not perform a facility-wide risk 

assessment based on allowable emissions, as explained in the 

documentation referenced in section IV.A of this preamble, which 

is available in the docket for this action. 

Table A.3. Chromium Electroplating and Anodizing Facility-Wide 

Risk Assessment Results

Source 

Category 

Maximum 

Facility-Wide 

Individual 

Cancer Risk 

(in 1 million)

Source 

category 

contribution 

to this 

maximum 

facility-wide 

individual 

cancer risk1

Maximum 

Facility-Wide 

Chronic Noncancer TOSHI 

Source 

category 

contribution 

to this 

maximum 

facility-wide 

chronic noncancer TOSHI1

Hard Chromium 

Electroplating 90 <1% 2 <1% 

Decorative 

Chromium 

Electroplating 

90 7% 0.8 <1% 

Chromium 

Anodizing 20 75% 0.2 <1% 

1

 Percentage shown reflects source category contribution to the maximum 

facility-wide risks at the facility with the maximum risk value shown. 

 As shown in Table A.3, the maximum individual cancer risks 

from all HAP emissions at facilities that perform hard chromium 
21

electroplating, decorative chromium electroplating, and chromium 

anodizing are estimated to be 90-in-1 million, 90-in-1 million, 

and 20-in-1 million, respectively. For the facilities where 

these maximum risk values occur, the estimated proportion of the 

cancer risk attributable to the hard chromium electroplating, 

decorative chromium electroplating, and chromium anodizing 

processes is less than 1 percent, 7 percent, and 75 percent, 

respectively. The highest facility-wide cancer risk for a 

facility that includes a hard chromium electroplating source is 

primarily driven by chemical production processes. We are 

currently developing a chemical manufacturing sector project5

 and 

plan to address risk from these chemical production processes as 

part of that action. The highest facility-wide cancer risk for 

a facility that includes a decorative chromium electroplating 

source is primarily driven by aerospace processes that will be 

addressed in a future residual risk review for the Aerospace 

Manufacturing and Rework Facilities source category. The 

highest facility-wide cancer risk for a facility that includes a 

chromium anodizing source is primarily driven by the chromium 

anodizing processes. The facility-wide maximum chronic noncancer TOSHI values for facilities that include Hard Chromium 

 

5

 This is one of several projects EPA is undertaking to establish and 

implement national emission-control measures for specific sectors of the 

economy by taking an integrated multipollutant approach to assessing and 

implementing additional emission controls using our existing regulatory 

frameworks. 
22

Electroplating, Decorative Chromium Electroplating, and Chromium 

Anodizing source category processes are estimated to be 2, 0.8, 

and 0.2, respectively. At the facilities where these maximum 

risk values occur, the estimated proportion of the non-cancer 

risk attributable to the Hard Chromium Electroplating, 

Decorative Chromium Electroplating, and Chromium Anodizing 

source category processes is less than 1 percent for each source 

category. 

 The results of the demographic analyses performed to 

investigate the distribution of risks above 1-in-1 million, 

based on actual emissions levels for the population living 

within 5 km of the facilities, among various demographic groups 

are provided in a report available in the docket for this action 

and summarized in Tables A.4, A.5, and A.6 below. These 

estimates of total population with risk exceeding 1-in-1 million 

differ from the risk estimates presented above because the 

demographic analysis uses a 5 km radius and the risk assessment 

results provided above reflect use of a 50 km radius around all 

chromium electroplating facilities. 

Table A.4. Hard Chrome Electroplating Demographic Risk Analysis 

Results 

Emissions 

Basis 

Maximum 

Risk Population With Risk Greater Than 1-in-1 million 
23

(in 1 

million

) 

Total 

(mill

ions) 

Ethnic 

Minorit

y 

% 

African 

America

n 

% 

Other 

and 

Multirac

ial 

% 

Hispani

c 

or 

Latino

% 

Native 

America

n 

% 

Below 

the 

Poverty 

Level 

% 

Over 

25 

W/O

a HS 

Diplo

ma 

% 

Nationwid

e n/a 285 25 12 12 14 0.9 13 13 

Source 

Category 70 13.1 52 23 29 34 0.6 22 20 

Facilitywide 90 13.1 52 23 29 34 0.6 22 20 

Table A.5. Decorative Chromium Electroplating Demographic Risk 

Analysis Results 

Population With Risk Greater Than 1-in-1 million 

Emissions 

Basis 

Maximum 

Risk 

(in 1 

million) 

Total 

(millio

ns) 

Ethnic 

Minorit

y 

% 

African 

America

n 

% 

Other 

and 

Multira

cial 

% 

Hispani

c 

or 

Latino

% 

Native 

America

n 

% 

Below 

the 

Pover

ty 

Level 

% 

Over 25 

W/O 

a HS 

Diploma

% 

Nationwid

e n/a 285 25 12 12 14 0.9 13 13 

Source 

Category 70 0.35 50 18 32 47 0.8 24 23 

Facilitywide 90 0.43 54 21 32 48 0.7 24 25 

Table A.6. Chromium Anodizing Demographic Risk Analysis Results 

Population With Risk Greater Than 1-in-1 million 

Emissions 

Basis 

Maximum 

Risk 

(in 1 

million) 

Total 

(millio

ns) 

Ethni

c 

Minor

ity 

% 

African 

America

n 

% 

Other 

and 

Multirac

ial 

% 

Hispani

c 

or 

Latino

% 

Native 

America

n 

% 

Below 

the 

Pover

ty 

Level 

% 

Over 25 

W/O 

a HS 

Diploma

% 

Nationwid

e 

n/a 285 25 12 12 14 0.9 13 13 

Source 

Category 

5 0.0027 36 16 0 0 0.4 25 19 

Facilitywide 

20 0.0079 22 10 12 13 0.8 19 16 
24

 The results of the demographic analysis show that, for the 

population located within 5 km of hard chromium electroplating 

source category, there are about 13.1 million people with cancer 

risks greater than 1-in-1 million for both the source category 

and facility-wide. Of this population at risk, 52 percent could 

be classified as an “Ethnic Minority,” 34 percent are included 

in the “Hispanic or Latino” demographic group, 29 percent are 

included in the “Other and Multiracial” demographic group, 23 

percent are included in the “African-American” demographic 

group, 22 percent are included in the “Below Poverty Level” 

demographic group, and 20 percent are included in the “Over 25 

Without a High School Diploma” demographic group. The 

percentage of the population within 5 km of a hard chromium 

electroplating facility and with a cancer risk greater than 1-

in-1 million is higher than the typical distribution of risks to 

these demographic groups across the United States. These 

demographic analyses are based on the conservative assessment 

results. 

 For the Decorative Chromium Electroplating source category, 

there are about 350,000 people with cancer risks greater than 1-

in-1 million for the source category and 430,000 people with 

cancer risks greater than 1-in-1 million facility-wide. Of this 

population at risk, 50 percent could be classified as an “Ethnic 

Minority” 47 percent are included in the “Hispanic or Latino” 
25

demographic group, 32 percent are included in the “Other and 

Multiracial,” demographic group, 18 percent are included in the 

“African-American” demographic group, 24 percent are included in 

the “Below Poverty Level” demographic group, and 23 percent are 

included in the “Over 25 Without a High School Diploma” 

demographic group. The percentage of the population within 5 km 

of a decorative chromium electroplating facility and with a 

cancer risks greater than 1-in-1 million is higher than the 

typical distribution of risks to these demographic groups across 

the United States. The results of the demographic analysis for 

facility-wide emissions are similar to the results for the 

source category. 

 For the Chromium Anodizing source category, there are about 

2,700 people with cancer risks greater than 1-in-1 million and 

7,900 people with cancer risks greater than 1-in-1 million 

facility-wide. Of the population with cancer risks greater than 

1-in-1 million, 36 percent could be classified as an “Ethnic 

Minority,” 16 percent are included in the “African-American” 

demographic group, 25 percent are included in the “Below Poverty 

Level” demographic group, and 19 percent are included in the 

“Over 25 Without a High School Diploma” demographic group. The 

percentage of the population within 5 km of a chromium anodizing 

facility and with a cancer risk greater than 1-in-1 million is 

higher than the typical distribution of risks to these 
26

demographic groups across the United States. The results of the 

facility-wide demographic analysis are higher than the typical 

distribution of risks to the demographic groups across the 

United States, for the “Below Poverty Level” and the “Over 25 

Without a High School Diploma” demographic groups, but are lower 

than these levels for the other demographic groups. 

 Details of these assessments and analyses can be found in 

the residual risk documentation as referenced in section IV.A of 

this preamble, which is available in the docket for this action. 

4. What are our proposed decisions on risk acceptability and 

ample margin of safety?

a. Risk Acceptability.

 The risk analysis we performed for this proposal indicates 

that for the hard chromium electroplating source category, the 

cancer risks to the individual most exposed is 70-in-1 million 

based on actual emissions and 90-in-1 million based on MACTallowable emissions. The maximum noncancer risk level, which is 

low, is a TOSHI of 0.06 based on actual emissions and 0.09 based 

on allowable emissions. These risks are due to estimated 

emissions of hexavalent chromium, which EPA describes as a known 

human carcinogen by the inhalation route of exposure. As 

explained above, both the MIR and the maximum noncancer risk 

levels are based on emissions from what we believe is the 
27

highest risk hard chromium facility operating in the United 

States. 

 We further estimate that the excess cancer incidence could 

be as high as 0.8 cases per year and that over 14 million people 

could be exposed to a cancer risk of 1-in-1 million or greater. 

These risk levels are based on a highly conservative risk 

assessment as described above. In summary, in this assessment 

we used (1) actual emissions data for 63 facilities and (2) 

emissions estimates that are reflective of average emissions for 

the highest emitting facilities for each one of an additional 

1,219 facilities. Because there are only 790 hard chromium 

facilities and because only ten percent of the facilities would 

have this high of an emissions rate, we believe that these 

conservative risk assessment results overstate cancer incidence 

and population exposure. 

 As noted above, we performed a supplemental analysis to 

assess the degree to which the conservative risk assessment may 

overstate risks, and thus to determine how heavily to weigh 

those risks in determining whether to find the risks acceptable. 

In this supplemental analysis we assessed these risks based on 

(1) the emission data used in the conservative assessment for 

the 63 facilities for which we have actual facility emission 

information, and (2) revised emission data that better represent 

nationwide average emission levels for the 1,219 facilities. 
28

The supplemental assessment indicates that the excess cancer 

risks from hard chromium electroplating facilities is 0.1 cancer 

cases per year and 360,000 people exposed to a cancer risk of 1-

in-1 million or more, which is substantially less than we found 

with the conservative assessment. These results indicate that 

the estimated risks are uncertain and are highly sensitive to 

input assumptions and that the conservative assessment may 

substantially overstate risks. 

 The results of our demographic analysis indicate that 

minorities face disproportionate risk from exposure to emissions 

from this category (Tables A.3 – A.5). Although the demographic 

analysis was based on our conservative risk assessment modeling, 

we have no reason to believe that the results would be 

substantially different were we to re-run that analysis using 

the assumptions underlying the supplemental assessment. This is 

because the disparate impacts identified through our demographic 

analysis are reflective of the fact that many chrome facilities 

are located in inner city urban areas, and in or near 

residential neighborhoods more likely to be inhabited by 

minority and low income persons. We are concerned about the 

potential disproportionate health risks from these urban 

facilities on minorities and those below the poverty level. We 

solicit comment on whether there may be pollution prevention 

efforts or other HAP emission reduction approaches that could 
29

mitigate the impacts that these facilities have on their 

immediate surroundings. We also recognize that in addition to 

whatever controls are required in the final rulemaking for the 

hard chromium electroplating category, there may be other 

approaches, such as facility-specific compliance assistance, 

that could mitigate the impacts that these facilities have on 

their immediate surroundings. We solicit comment and supporting 

information to assist EPA in identifying measures to mitigate 

these disproportionate risks. 

 In accordance with the approach established in the Benzene 

NESHAP, EPA weighed all health risk measures and information, 

including the maximum individual cancer risk, the cancer 

incidence, the number of people exposed to a risk greater than 

1-in-1 million, the distribution of risks in the exposed 

population, and the uncertainty of our risk calculations, in 

determining whether the risk posed by emissions from hard 

chromium facilities is acceptable. 

 As an initial matter, we note that the 90-in-1 million risk 

based on allowable emissions is approaching the “presumptive 

limit on maximum individual lifetime risk of approximately 1 in 

10 thousand [100-in-1 million]” recognized in the benzene NESHAP 

(54 FR 38045). We also note that, based on our conservative 

analysis, there is a high level of cancer incidence of 0.8 and a 

very large number (14.2 million) of people potentially exposed 
30

to a cancer risk greater than 1-in-1 million. However, we also 

recognize that our supplemental assessment based on alternative 

input assumptions concerning emissions (that better represent 

nationwide average emissions) indicate that the results of the 

conservative assessments are substantially overstated. Thus, 

there is great uncertainty about both the cancer incidence and 

the number of people exposed. 

 On the one hand, we acknowledge that the cancer incidence 

and number of people exposed to cancer risks of 1-in-1 million 

or greater are high based on our conservative analysis. On the 

other hand, we recognize the significant uncertainty of these 

risk estimates and the likelihood that they are overstated, 

based on the conservative nature of the assessment. The 

supplemental analysis highlights the sensitivity of our risk 

analysis to highly uncertain input assumptions and supports a 

determination that the population exposure and cancer incidence 

risk numbers are overstated. It shows substantially lower 

cancer incidence (0.1 cases per year as opposed to 0.8) and 

number of people potentially exposed to a cancer risk of 1-in-1 

million or more (360 thousand as opposed to 14.2 million). In 

addition, the distribution of risks in the exposed population 

shows the number of people exposed to a cancer risk greater than 

10-in-1 million is 71,000 for the conservative assessment and 

5,100 for the supplemental analysis. 
31

In determining whether risk is acceptable, we focus on the 

results of all aspects of the risk assessment. Because the MIR 

is less than 100-in-1 million and because of the significant 

uncertainty of the cancer incidence and number of people 

exposed, which, as explained above, we believe are overstated 

based on the fact that our risk analysis was highly 

conservative, at this time, we are proposing that the risks from 

the hard chromium electroplating source category are acceptable. 

We are proposing that the risks are acceptable, in large part, 

because we believe that the assumptions underlying the 

supplemental analysis may present a more realistic estimate of 

the emissions from hard chromium facilities. 

However, we are very concerned by the results of our 

conservative risk analysis, especially the large number of 

people (including disproportionately affected populations) 

estimated to be exposed at a cancer risk above 1-in-1 million. 

We are also concerned about the level of uncertainty with our 

analysis given that we have very limited information as to the 

number (and size) of the facilities. While our current proposal 

is supported by recognizing the uncertainty associated with the 

high risk levels from our conservative assessment and, as 

explained above, that uncertainty (as demonstrated by the 

supplemental analysis) points in the direction of an 

overstatement of risk, we would prefer to base a final rule on 
32

more complete and reliable information. In this case, we 

recognize that the assessment may be overly conservative and we 

are considering additional methods for performing a conservative 

analysis. However, we believe additional information and data 

regarding the location, type and size of facilities will be 

important to performing any additional analysis that would err 

on the side of protectiveness without being overly conservative. 

At this time, we are not certain that we would take final action 

finding the risk to be acceptable based on the limited 

information currently available to the Agency. 

The comments and information that we receive on this 

proposal will be critical in making a final decision on 

acceptability. We are soliciting comment and data to help the 

Agency make an informed decision as it moves forward with this 

rulemaking. Specifically, with regard to each of the facilities 

listed in Appendix A to this preamble, we are seeking to 

identify (1) the actual annual emissions, if known; (2) which of 

the three source categories it falls within; and (3) whether, 

for hard chromium, it is a “large” or “small” facility within 

the definitions in 40 CFR 63.341(a). In particular, we are 

encouraging the States to provide EPA with better inventory data 

for sources within their states. Moreover, we are encouraging 

States to help identify sources that may be located near 

sensitive populations, such as located near schools or that may 
33

be located in communities with a significant minority 

population. To feel comfortable with a final decision finding 

the risk acceptable, we believe it is important to reduce the 

level of uncertainty associated with our current analyses. 

Thus, in light of the comments and any additional data (or lack 

thereof) that we receive during the comment period, we may 

determine that it is appropriate to issue a supplemental 

proposal in which we propose to find the risk unacceptable. If 

we issue a supplemental proposal in which we propose to find the 

risk unacceptable, we would be required to propose emissions 

standards or work practices that reduce risk to a level that is 

acceptable and provides an ample margin of safety. 

We note that we have a proposed draft Consent Decree, 

Sierra Club v. EPA (N.D. Cal., No. 09-cv-00152SBA) (Consent 

Decree lodged with Court on July 6, 2010), which would require 

us to take final action under CAA 112(f)(2) for the Chromium 

Electroplating source category by June 30, 2011. If, after the 

close of the comment period, we conclude that it is necessary to 

issue a supplemental proposal, we would plan to seek an 

extension of that Consent Decree deadline to provide sufficient 

time for that process. 

 For the decorative chromium electroplating source category, 

the cancer risks to the individual most exposed is 70-in-1 

million based both actual and MACT-allowable emissions. Based 
34

on this cancer risk level and in consideration of other health 

measures and factors, including the cancer incidence (one case 

in every 12.5 years) and the low maximum noncancer risk level 

(TOSHI of 0.06 based on both actual and MACT-allowable 

emissions), we propose that the risks from the decorative 

chromium electroplating source category are acceptable. 

 For the chromium anodizing source category, the cancer 

risks to the individual most exposed is 5-in-1 million based on 

both actual and allowable emissions. Based on this low cancer 

risk level and in consideration of other health measures and 

factors, including the cancer incidence (one case in every 250 

years) and the low maximum noncancer risk level (TOSHI of 0.004 

based on actual emissions), we propose that the risks from the 

chromium anodizing source category are acceptable. 

b. Ample Margin of Safety.

 Although we are proposing that the risks from these source 

categories are acceptable, risk estimates for individuals in the 

exposed population are above 1-in-1 million. Consequently, we 

considered whether the MACT standard provides an ample margin of 

safety. As part of this analysis, we investigated available 

emissions control options that might reduce the risk associated 

with chromium compound emissions from hard chromium 

electroplating, decorative chromium electroplating, and chromium 
35

anodizing operations. Table A.6 summarizes the nationwide costs 

and cost effectiveness of these regulatory control options. 

Table A.6. Costs of Control Options for Chromium Electroplating 

Type of 

facility 

Control 

Option 

Number of 

Affected 

Facilities 

Emission 

reduction 

(TPY) 

Capital 

costs 

($million) 

Annualiz

ed costs 

($millio

n/yr) 

Costeffectiven

ess 

($million/

ton) 

MIR After 

Control 

(in-amillion)

Large hard 

chromium 

electroplating 

HEPA 

filter 

retrofit 

132 1.0 35.1 18.4 17.7 

6 

HEPA 

filter 

retrofit 

658 0.4 66.0 33.9 84.9 

6 

Small hard 

chromium 

electroplating CMP 

retrofit 392 0.2 36.6 11.1 59.7 10 

HEPA 

filter 

retrofit 

740 0.1 109.0 50.6 513.9 

4 

Decorative 

chromium 

electroplating CMP 

retrofit 644 0.051

 41.3 22.2 886.1 10 

HEPA 

filter 

retrofit 

240 0.02 43.9 18.9 945.0 

< 1 

Chromium 

anodizing CMP 

retrofit 198 0.0091

 16.1 7.4 1860 2 

1 Based on an estimated control efficiency of 99.9 percent.

 For large hard chromium electroplating facilities, we 

evaluated the costs and emissions reductions associated with 

retrofitting existing tanks with HEPA filters. For small hard 

chromium electroplating facilities, we evaluated the same HEPA 

filter retrofit option and also the option of retrofitting CMP 

systems on all tanks currently controlled with packed bed 

scrubbers. Retrofitting HEPA filters on existing tanks at large 

hard chromium electroplating plants would reduce nationwide 

emissions of chromium compounds by an estimated 1.04 TPY from 

the estimated baseline level of 1.10 TPY. The estimated capital 

and annualized costs for this option would be $35,100,000 and 

$18,430,000, respectively. The cost effectiveness would be 

$17,700,000 per ton of HAP emissions reduced. Retrofitting HEPA 
36

filters on existing tanks at small hard chromium electroplating 

plants would reduce nationwide emissions of chromium compounds 

by an estimated 0.40 TPY from the estimated baseline level of 

0.42 TPY. The estimated capital and annualized costs for this 

option would be $65,980,000 and $33,860,000, respectively. The 

cost effectiveness would be $84,900,000 per ton of HAP emissions 

reduced. Retrofitting CMP systems on all tanks currently 

controlled with packed bed scrubbers at small hard chromium 

electroplating plants would reduce nationwide emissions of 

chromium compounds by an estimated 0.19 TPY from the estimated 

baseline level of 0.37 TPY. The estimated capital and 

annualized costs for this option would be $36,640,000 and 

$11,050,000, respectively. The cost effectiveness would be 

$59,700,000 per ton of HAP emissions reduced. The Benzene 

NESHAP emphasizes the need to consider “costs and the economic 

impacts of control” which implies some knowledge of 

affordability (54 Fed. Reg. 38046). The cost of the control 

options for hard chromium electroplating would impact over half 

of these facilities with estimated cost to sales ratios ranging 

from 8% to 22%. A cost to sales ratio greater than 3% may have 

a significant impact, including plant closure for many of these 

facilities. 

 These additional control requirements would reduce the 

maximum lifetime individual cancer risk from the Hard Chromium 
37

Electroplating source category to approximately 4-in-1 million, 

based on actual emissions. We estimate that considering MACTallowable emissions levels, the maximum lifetime individual 

cancer risk from the Hard Chromium Electroplating source 

category would be reduced to approximately 6-in-1 million. The 

cancer incidence would be reduced to approximately 0.05 and the 

estimated number of people exposed higher than 1-in-1 million 

would be about 1 million. 

For decorative chromium electroplating, we evaluated the 

options of retrofitting HEPA filters on all existing tanks and 

the option of retrofitting CMP systems on the existing tanks 

that currently are not equipped with add-on control devices. 

Retrofitting HEPA filters on all existing decorative chromium 

electroplating tanks would reduce nationwide emissions of 

chromium compounds by an estimated 0.098 TPY from the estimated 

baseline level of 0.10 TPY. The estimated capital and 

annualized costs for this option would be $108,970,000 and 

$50,600,000, respectively. The cost effectiveness would be 

$513,900,000 per ton of HAP emissions reduced. Retrofitting CMP 

systems on all decorative chromium electroplating tanks that 

currently do not have add-on controls would reduce nationwide 

emissions of chromium compounds by an estimated 0.05 TPY from 

the estimated baseline level of 0.10 TPY. The estimated capital 

and annualized costs for this option would be $41,300,000 and 
38

$22,190,000, respectively. The cost effectiveness for this 

option would be $886 million per ton of HAP emissions reduced. 

The additional control requirements for HEPA filters would 

reduce the maximum lifetime individual cancer risk from the 

Decorative Chromium Electroplating source category to 

approximately 4-in-1 million, based on actual emissions. 

Because we believe the actual emissions are essentially the same 

as the MACT-allowable emissions for the Decorative Chromium 

Electroplating source category, we estimate no difference 

between the risk from the allowable emission level and the 

actual emission level. 

 For chromium anodizing, we evaluated the options of 

retrofitting HEPA filters on all existing tanks and the option 

of retrofitting CMP systems on the existing tanks that currently 

are not equipped with add-on control devices. Retrofitting HEPA 

filters on all existing chromium anodizing tanks would reduce 

nationwide emissions of chromium compounds by an estimated 0.020 

TPY from the estimated baseline level of 0.021 TPY. The 

estimated capital and annualized costs for this option would be 

$43,860,000 and $18,860,000, respectively. The costeffectiveness would be $944,800,000 per ton of HAP emissions 

reduced. Retrofitting CMP systems on all chromium anodizing 

tanks that currently do not have add-on controls would not 

significantly reduce emissions. The estimated capital and 
39

annualized costs for this option would be $16,130,000 and 

$7,430,000, respectively. The cost effectiveness for this 

option would be $1,860 million per ton of HAP emissions reduced. 

The additional control requirements for HEPA filters would 

reduce the maximum lifetime individual cancer risk from the 

Chromium Anodizing source category to less than 1-in-1 million, 

based on actual emissions. Because we believe the actual 

emissions are essentially the same as the MACT-allowable 

emissions for the Chromium Anodizing category, we estimate the 

risk reduction based on allowable emissions to be the same as 

that for the actual emissions. 

Our risk analysis results show cancer risks to the 

individual most exposed of 70-in-1 million and 5-in-1 million 

based on actual and MACT-allowable emissions, respectively, for 

the Decorative Chromium Electroplating and Chromium Anodizing 

source categories. For both of these categories, the cancer 

incidence is less than 0.01 cases/year. For decorative chromium 

electroplating, the number of people exposed to a cancer risk of 

1-in-1 million or more is approximately 390,000. For chromium 

anodizing, the number of people exposed to a cancer risk of 1-

in-1 million or more is approximately 2,700. 

For the Hard Chromium Electroplating source category, our 

risk analysis shows cancer risks to the individual most exposed 

are 70-in-1 million based on actual emissions levels and 90-in-1 
40

million based on MACT-allowable emissions. The cancer incidence 

for this source category could be as high as 0.8 cases/year, and 

could be over 14 million people exposed to cancer risks of 1-in1 million or greater due to emissions from hard chromium 

electroplating sources using highly conservative assumptions. 

As we stated previously, we believe we overestimated hard 

chromium electroplating emissions, the number of plants that 

perform hard chromium electroplating, and therefore that the 

risks from the resulting analyses are also overstated. Our 

supplemental risk analysis for this source category indicates a 

cancer incidence of 0.1 cases/year and 360,000 people exposed to 

cancer risks of greater than 1-in-1-million. This analysis 

indicates that the risk levels in the assessment are highly 

uncertain and err on the side of being conservative. 

Our analyses also show that, for these source categories, 

there is no potential for an adverse environmental effect or 

human health multipathway effects, and that acute and chronic 

non-cancer health impacts are unlikely. Our additional analysis 

of facility-wide risks showed that the maximum facility-wide 

cancer risk is 90-in-1 million and that the maximum chronic noncancer risks are unlikely to cause health impacts. Our 

additional analysis of the demographics of the exposed 

population shows that minorities face disproportionate risk from 

exposure to emissions from this category 
41

We do not believe there is a significant risk reduction 

from the housekeeping measures we are proposing under 112 

(d)(6). However, we are requesting information on any risk 

reductions from these housekeeping practices and whether we 

should consider adopting these practices under 112 (f)(2). 

We considered all these factors in our ample margin of 

safety decision, and concluded that the costs of the options 

analyzed are not reasonable considering the emissions reductions 

and cancer health benefits potentially achievable with the 

controls. As a result, we propose that the existing MACT 

standard provides an ample margin of safety (considering cost, 

technical feasibility, and other factors) to protect public 

health for all three of these source categories. Thus, we are 

proposing to re-adopt the existing MACT standard to satisfy 

section 112(f) of the CAA. 

 While we propose that the existing MACT standard for the 

hard chromium electroplating source category is acceptable and 

provides an ample margin of safety, we are proposing additional 

requirements under CAA section (d)(6), as discussed below. 

Notwithstanding our proposal that the risks are acceptable, we 

remain concerned that up to 14.2 million people may be exposed 

to cancer risks of 1-in-1 million or greater and that there are 

disparities in risks for some demographic groups. While we are 

rejecting the option of adding HEPA filters or composite mesh 
42

pads as not cost-effective, we are specifically requesting 

comment on whether there are any cost-effective controls that 

may be able to reduce these risks. In particular, we are 

requesting States to identify any controls they have already 

required for these facilities, any controls they are currently 

considering, or any other controls of which they may be aware. 

We are also soliciting comment on whether our cost estimates for 

these options are accurate and whether these controls may be 

more cost-effective. 

 In summary, we propose that the risks posed by these source 

categories are acceptable. We are also proposing that the 

current MACT standard provides an ample margin of safety to 

protect public health based on our conclusion that the controls 

available are not cost-effective in light of the additional 

health protection the controls would provide. Thus, we are 

proposing to re-adopt the existing MACT standard to satisfy 

section 112(f) of the CAA.