OAR Box 1875 

Prepped by Ollie Stewart 

Document Number: 

35) ll-E-53 

Docket Number: 

A-90-19 

Printed 12/1/2008 11:12:46 AM Sheet 35 of 86 

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A-90-19 

ll-E-53 

DATE: August 19, 1992 

SUBJECT: Hazardous Organic NESHAP (HON) Meeting with State 

Representatives 

The following EPA personnel participated in a teleconference with 

the National Governors Association's Air Implementation Task 

Force: Bruce Jordan, Director of the Emissions Standards 

Division; Jane Caldwell-Kinkel and Karen Blanchard, Pollutant 

Assessment Branch; and Jan Meyer and Daphne McMurrer, Standards 

Development Branch. Attached are an agenda for the 

teleconference, a list of NGA invitees, and an issue paper on 

interpollutant trading provided by EPA to those participating in 

the teleconference. 

Attachments: 3 

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.N^ONAL 

GOVERNORS' 

ASSCEI/OION 

Roy Romer 

Governor of Colorado 

Chairman 

Raymond. C. Scheppicb 

Executive Director 

Hall of the States 

444 North Capitol Street 

Washington. D.C. 20001-1572 

Telephone (202) 624-5300 

P.3 

••** * 

**** * 

EPA BRIEFING ON THE HON 

CONFERENCE CALL AGENDA 

State Environmental Commissioners' 

Air Implementation Task Force 

Wednesday, August 19, 1992, 2:00 p.m. EST 

Conference Line: 202/296-3132 

Introduction and Update on HON Schedule 

Update on EPA/OMB Discussions and Strategy for Promulgation 

EPA Comments on States' Proposed Discount Factor System 

Overview of the 112(g) Interpollutant Trading System 

Conclusion 
P.4 

The following state officials have been invited to participate in the August 

19 HON Conference Call: 

State Commissioners on the Air Implementation Task Force 

Ken Alkema, Executive Director, Utah Department of Environmental Quality 

James Boyd (for Jan Sharpless), Executive Director, California Air Resources 

Board 

Mark Coleman, Deputy Commissioner, Oklahoma State Department of Health 

Dan Greenbaum, Commissioner Massachusetts Department of Environmental 

Protection 

Tom Looby, Director, Office of Environment, Colorado Department of Health 

Bharat Mathur (for Mary Gade), Manager, Air Pollution Control Division, 

Illinois Environmental Protection, Agency 

Bob Perciasepe, Secretary, Maryland Department of the Environment 

Lewis Shaw, Deputy Commissioner, Environmental Quality Control, South Carolina 

Department of Health and Environmental Control 

Scott Weiner, Commissioner, New Jersey Department of Environment and Energy 

STAPPA Participant on Air Implementation Task Force's HOB Work Group 

Tad Aburn, Program Administrator, Air Management Administration, Maryland 

Department of the Environment 

Karen Olson, Section Chief, FTATS, Texas Air Control Board 

Bill 0'Sullivan, Administrator, Office of Energy, New Jersey Department of 

Environmental Protection and Energy 

Donald Theiler, Director, . Air Management Bureau, Wisconsin Department of 

Natural Resource 
P.5 

BACKGROUND 

One interpretation of the language of section 112(g) allows increased emissions 

of a HAP due to a modification to be offset by an equal or greater amount of "a 

more hazardous pollutant". Under the more "hazardous pollutant" approach, 

EPA's task is to determine the relative hazard of one pollutant to another. 

The alternative interpretation of the language in 112(g) allows offsets of 

increased emissions of a HAP to be offset by "a more hazardous quantity of 

another pollutant". Under this interpretation, a more hazardous quantity may 

be used as an offset regardless of the whether the offsetting pollutant is itself 

"more hazardous". Under this approach not only must the relative hazard of the 

pollutants be established but also the magnitude of the difference in hazard 

between pollutants. 

Staff are currently working to develop "dual proposals" for the hazard ranking 

guidance. The proposed guidance will direct public comment on these two 

interpretations of the language in 112(g) specifically but Will also mention as an 

alternative a "limited indexing" approach. Under this approach an equal or 

greater quantity of a "more hazardous pollutant" or a more hazardous amount 

of an "equally hazardous" pollutant will be allowed as offsets. 

THE HAZARD RANKING 

I. How the pollutants are categorized. 

n. What the relative hazard of each category is. 

HI. What offsets are allowed within and between categories. 
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I. Categorization. 

The language in section 112(g) prohibits emissions of pollutants with no safety 

threshold of exposure to be offset by those with a safety threshold of exposure. 

Consequently the EPA must separate the pollutants accordingly. 

Currently, the proposed hazard ranking guidance places carcinogens (those 

pollutants which are known, probable, or possible human carcinogens) into the 

"non-threshold" category of pollutants. All other pollutants are assumed to have 

a safety threshold of exposure unless there is evidence to the contrary. 

There are two more categories of pollutants in the proposed hazard ranking 

guidance to which pollutants may be assigned. One is for "high-concern" 

pollutants which exhibit either severe acute or chronic toxicity from relatively 

low concentrations. The other is for pollutants with insufficient data to rank. 

n. Relative hazard between categories. 

As a policy decision the relative hazard of each category is as follows: 

1. "Non-threshold" pollutants are considered as a category to be more 

hazardous than "threshold" pollutants. 

2. "High-concern" pollutants are also considered to be more hazardous than 

"threshold" pollutants. 

3. However the relative hazard between "non-threshold pollutants and "highconcern" pollutants cannot be established. 

4. The relative hazard of "unrankable" pollutants to the other categories of 

pollutants cannot be established. 
P.7 

UI. Allowable offsets between and within categories. 

1. Proposed approach for a "more hazardous pollutant" interpretation of the 

language in 112(g) 

"Non-threshold" pollutants 

The relative hazard of carcinogens is determined by their carcinogenic 

potency (1/ED10) and weight of evidence. Potency is described by the 

dose in which there is carcinogenic response of 10%. 

Known and probable human carcinogens may be used to offset each other 

using only potency as the basis for relative hazard. Possible human 

carcinogens are never considered to be more hazardous than known or 

probable human carcinogens. 

Carcinogens are not assigned to "fixed bins" of hazard. The potencies of 

two carcinogens are compared and if the difference in potency between 

them exceeds a half an order of magnitude then one may be considered to 

be more hazardous than another (policy decision). If the potency 

estimates of two carcinogens are within a half an order of magnitude of 

each other then they are considered to be equally hazardous. 

Carcinogens with a weight of evidence determination but no potency 

estimate are not allowed to be offset or as offsets for other carcinogens. 

They are however as a category considered to be more hazardous than 

threshold pollutants and are therefore available as offsets for increased 

emissions of threshold pollutants. 
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"Threshold" pollutants 

The relative hazard of non-carcinogens is determined by their chronic 

toxicity. The relative hazard is expressed as a composite score which 

takes into account both the potency of each pollutant and the severity of 

the effect a minimal equivalent human dose elicits. The composite score 

methodology was derived for section 102 of CERCLA or "Superfund" to 

relatively rank hazardous pollutants by their chronic toxicity. 

"Threshold" pollutants may be used to offset each other using the 

composite score as a basis for relative hazard. 

"Threshold pollutants are also not assigned to "fixed bins" of hazard. The 

composite scores of two pollutants are compared and if the difference in 

potency exceeds 4 composite score units then one may be considered to 

be more hazardous than another. If the composite score of two pollutants 

are within 4 composite score units then they are considered to be equally 

hazardous (policy decision). 

"High-concern" pollutants 

Pollutants which are of high concern for acute toxicity are identified by 

a low "Level of Concern" value from the SARA Title HI - Extremely 

Hazardous Substances List (section 302). These pollutants are placed in 

the "high-concern" category for the hazard ranking and are not available 

as offsets or to offset any other pollutant within "high-concern" category. 

Pollutants which are of high concern for severe chronic toxicity at 

relatively low doses are identified by a relatively high composite score. 

Such pollutants may offset each other according to the rules established for 

other "threshold" pollutants. 

"Unrankable" pollutants 

Pollutants which do not have adequate data to rank in the other categories 

are assigned to this category and not available as an offset or to be offset 

by any other pollutants. 
P.9 

2. Proposed approach for a "more hazardous quantity" interpretation 

of the language in section 112(g) 

Under this paradigm not only must the EPA determine the relative hazard 

but also the magnitude of difference in hazard between pollutants. 

The proposed guidance for this interpretation of 112(g) is still under 

internal agency review. 

Under this approach the categorization and relative hazard of each 

category of pollutant would be consistent with the "more hazardous 

pollutant" interpretation. 
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EXAMPLES OF IMPLEMENTATION OF THE PROPOSED 112(g) 

GUIDANCE 

"A MORE HAZARDOUS POLLUTANT" APPROACH 

1. Joe Blow comes to a State Agency and asks for approval of an offset. Joe 

wants to modify his plant and increase the amount of an Hazardous Air 

Pollutant (HAP) that has no safety threshold of exposure (i.e. for 

discussion purposes a carcinogen). He is proposing the following offset 

to comply with Section 112(g) of the CAA. 

Joe wants to increase his emissions of trichloroethylene by 10 tons. Joe 

proposes to offset his trichloroethylene emissions increase with a decrease 

of 10 tons of benzene. 

As the reviewing authority you must determine whether this offset will 

satisfy the requirements of 112(g). The following criteria must be met: 

a. Is benzene a "more hazardous pollutant" than trichloroethylene? 

i. Is the potency of benzene at least 3 times that of 

trichloroethylene? 

yes, 1/ED10 of benzene is 0.27 vs 0.035 for 

trichloroethylene 

ii. Is the weight of evidence of benzene comparable to 

trichloroethylene? 

yes, benzene has a weight of evidence classification of 

A (known human carcinogen) whereas trichloroethylene 

has a B/C (considered as a probable human carcinogen 

for purposes of this guidance) classification. 

* according to the guidance, a carcinogen with a weight 

of evidence classification of A or B may be offset by 

another with a weight of evidence or A or B, however 

a C carcinogen is never considered to be more 
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hazardous than an A or B carcinogen regardless of 

potency. Carcinogens with a weight of evidence of C 

can be offset by other Cs. 

b. Is Joe reducing an equal or greater quantity of Benzene for his 10 

ton increase in trichloroethylene? 

yes, 10 tons is being offset with 10 tons. 

Therefore Joe's offset would be allowed according to the guidance set forth 

under Section 112(g). 

2. Could Joe use any of the following pollutants to offset his 10 ton increase 

in trichloroethylene? 

a. "Threshold" pollutant? (e.g. toluene) 

no, as a category "threshold" pollutants are considered to be 

less hazardous than "non-threshold" pollutants. 

b. "High-concern" pollutants (e.g. acrolein) 

no, as a category the relative hazard between "high-concern" 

and "non-threshold" pollutants can not be determined. 

c. "Unrankable" pollutants (e.g. radionuclides) 

no, as a category the relative hazard between "unrankable" 

pollutants and all other categories of pollutants can not be 

determined. 

3. What if Joe wants to increase emissions of a "threshold" pollutant? Joe 

wants to increase his emissions of methyl tert-butyl ether by 10 tons and 

use a decrease in emissions of 10 tons of hydrochloric acid as an offset. 

Again as the reviewing authority you must determine whether this offset 

will satisfy the requirements of 112(g). The following criteria must be 

met: 
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a. Is hydrochloric acid a more hazardous pollutant? 

i. Is the composite score for hydrochloric acid at least 4 

composite score units greater than that for methyl tert-butyl 

ether? 

yes, the composite score for methyl tert-butyl ether is 6 and 

that of hydrochloric acid is 11. 

b. Is joe reducing an equal or greater quantity of hydrochloric acid for 

his 10 ton increase in methyl tert-butyl ether? 

yes, 10 tons is being used as an offset for 10 tons 

Would Joe be able to offset his 10 ton increase in methyl tert-butyl ether 

with a reduction of 10 tons of xylene? 

a. Is xylene more hazardous than methyl tert-butyl ether? 

no, xylene would be considered equally hazardous in 

comparison to methyl tert-butyl ether. 

Under a strict "more hazardous pollutant" interpretation of 112(g) an equally 

hazardous pollutant would not be allowed to offset increased emissions due to 

a modification. 

The preamble of the proposed guidance will mention a derivation of the "more 

hazardous pollutant" approach discussed above as a "limited indexing approach". 

Under this alternative, a 125% decrease in an equally hazardous pollutant would 

be an allowable offset. 
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Ranking of pollutants with "CAS #s" 

by Hazard to Human Health 

Are offsets allowed? 

"High-concern" 

Pollutants 

10 acute nc 

10 acute c 

10 chronic nc 

Yes 

"Non-threshold" 

pollutants 

with WOE and w/wo 

potency (ED10) 

110 

Yes 

"Threshold" 

pollutants 

40 

Not enough 

data to rank 

10