# Risk and Technology Review **-**

**Analysis of Socio -**  **Economic Factors for Populations Living Near**  **N atural Gas**  **Transmission & Storage**

**Facilities**

Prepared b y: EC/R Incorporated 501 Eastowne Drive, Suite 250 Chapel Hill, NC 27514

EPA Contract No. EP
- D
- 06
- 1 19 Work Assignment No. 4
- 02
Prepared for: Terri Hollingsworth, Work Assignment Manager Sector Based Assessment Group Office of Air Quality

Planning and Standards U.S. Environmental Protection Agency Research Triangle Park, North Carolina 27 711

July 2011

### ii 

## Disclaimer Although the anal ys is described in this document has been funded wholly or in part by

the United States Environmental Protection Agency contract EP
- D
- 06
- 119 to EC/R Incorporated, it has not been subject to the Agency 's review and theref ore does not necessarily

reflect the views of the Agency , and no official endorsement should be inferred.

# Contents

1. Introduction 1 2. Census Data 2 3. Calculation Methods 3 3.1 Racial and Ethnic Categories and the Total Population 4 3.2 Age Categories 5 3.3 Level of Education 5 3.4 Household Income 6 3.5 Poverty

L evel 7 4. Results 7 5. Uncertaint y Discussion 8

### iv

### 1



# 1. **Intr oduction** 
This document describes the approach used to evaluate the potential cancer risks associated with inhalation and air
- related exposures to hazardous air pollutants (HAP) in different social, demographic , and economic groups withi n the populations living near natural gas transmiss i on and storage facilities in the United States
. This work was carried out in support of the U.S. Environmental Protection Agency ’s Residual Risk and Technology Review (RTR) for natural gas transmiss i on and storage operations emissions subject to Maximum Available Control Technology

(MACT) requirements under 40 CFR 63 Subpart HH H
. In the RTR anal ys is, the Human Exposure Model, Version 3 (HEM3) 1 , 2 

### was used to estimate cancer and noncancer risks due to the inhalation of HAP for the populations residing within 50 kilometers of each natural gas transmiss i on and storage facility in the country
. HEM3 estimates cancer and noncancer risks at the level of census blocks using the AERMOD state
- of
the
- art air disp ersion model developed under the direction of the American Meteorological Society (AMS) / EPA Regulatory Model Improvement Committee (AERMIC). Each census block ty pically includes about 50 people. Additional information on the risk anal ys is is available in the docket for the proposed **National Emission Standards for Hazardous Air Pollutant Emissions:**  **Natural G**  **as T**  **ransmiss i**  **on and S**  **torage Operations**  rulemaking wh ere a report is provided , covering the inputs and specific assumptions, and addressing uncertaint ies. In the current anal ys is, cancer risk estimates from the natural gas transmiss i on and storage HEM3 modeling effort were linked to detailed census data in order to evaluate the distribution of risks for different social, demographic and economic group s. (The RTR anal ys is estimated all noncancer hazard indices to be less than one for the natural gas transmiss i on and storage source category ; therefore a demographic anal ys is of potential noncancer impacts is not presented.) The following population cate gories were included in this analy sis :

 Total population  White  Minority  African American (or Black)  Native Americans  Other races and multiracial  Hispanic or Latino  Children 18 y ears of age and under
1
. EC/R. 2006. Modeling for the Residual Risk and Technology Review Using the Human Exposure Model 3

– AERMOD Version. Prepared by EC/R Incorporated for the U.S. Environmental Protection Agency, Research Triangle Park, NC. 2
. EC/R. 2008. HEM
- 3 User’s Guide. Prepared by EC/R Incorporated for the U.S. Environmental Protection Agency, Research Triangle Park, NC. http://www.epa.gov/ttn/fera/human_hem.html#guide

### 2

 Adults 19 to 64 y ears of age  Adults 65 y ears of age and o ver  Adults without a high school diploma  Households earning under the national median income  People living below the poverty line The HEM3 results for a particular census block reflect the level of risk that would be experienced b y an individual residing in the block for 70 y ears. The distributions of source category risks across the various demographic groups were compared to those associated with HAP sources at the facilities containing the source category (i.e., “facility
- wide”) , and to nationwide dis tributions of each of the demographics groups. The census data used in this analy sis is described in Section 2. The algorithms used to compute the distributions of risk and exposure are presented in Section 3. The results of this anal ys is are present ed in Section 4. 

# 2. **Census Data** Table 1 summarizes the census data used in this analy sis, showing the source of each dataset and the level of geographic resolution. All of the data are from the 2000 Decennial census. Race and ethnicity data were obtain ed at the census block level. Age distributions, data on educational status, and economic data were obtained at the block group level. A census block contains about 50 people on average; and a block group contains about 26 blocks on average, or about 1,3 50 people. (For comparison, a census tract is larger than a block group, with each tract containing an average of 3 block groups, or about 4,300 people.) Table 1. Summary

of Census Data used to Anal yz e Risks for Different Socio
economic Groups Ty pe of population category Source of data Level of geographic resolution Racial and ethnic categories Landview ® Census block Age groups SF3 Table P8 Block group Level of education
- a dults without a high school diploma SF3 Table 37 Block group Households ear

ning below the national median income SF3 Table 52 Block group People living below the poverty line SF3 Table P87 Block group

### 3

Data on race and ethnicity were obtained primarily

from the Landview ® database compiled by

the Census Department. 3 

### Landview ® gives a breakdown for the population of each census block among different racial classifications, including: White, African American or Black, American Indian or Native Alaskan, Asian, Native Hawaiian or other South Pacific Islander, other race, and two o r more races. In the current anal ys is, the Asian, Native Hawaiian or other South Pacific Islander, and other race categories were combined into a single category
. The Landview ® database also indicates the number of people in each tract that are of Hispan ic or Latino ethnicity . Landview ® covers the 50 states, the District of Columbia, and Puerto Rico, but does not cover the Virgin Islands. Race and ethnicity data on the Virgin I slands were obtained from the Virgin Islands Summary File. 4 

### Data on age dis tributions, poverty status, household incomes, and education level in the U.S. and Puerto Rico were obtained from the 2000 Census of Population and Housing Summary File 3 (SF3) Long Form. For the U.S. this file was accessed on a DVD version prepared b y Ge oLy tics. 5 

### SF3 data for Puerto Rico were obtained from the Census Department website, 6 

### and d ata for the Virgin Islands were retrieved from similar tables in the Virgin I slands Summary File. 4 

### The SF3 data set consists of over 800 separate tables , each pr oviding information on a different subject. For the current anal ys is, data were obtained from Table s P 8, P37, P52, and P87. Table P8 gives the estimated numbers of men and women in different age categories for each census block group. Table P37 anal yz es the level of education attained by men and women over 25 years of age (e.g. some high school but no high school diploma, high school graduate, some college, etc.). Table P52 gives information on household income in 1999 , and Table P87 estimates the numbe r of people living below the poverty line in each block group. 

# 3. **C alculation Methods**  The HEM3 models the cancer risk at a point near the geographic center of each census block. 7 

### For the current analy sis, this risk estimate was assumed to appl y to all i ndividuals residing in the block. We used b lock identification code s to link the HEM3 modeling results for 3
. Census. 2002 . LandView 5 on DVD [electronic resource] : a viewer for EPA , Census and USGS data and maps . U.S. Census Bureau, Washington, D.C. 4
. Census. 2008. Virgin Isl ands Summary File. U.S. Census Bureau, Washington, D.C. www.factfinder.census.gov 5
. Census. 2004 . Census DVD 2000 Long Form SF3, Release 2.2. Geolytics, Inc. , East Brunswick, NJ. www.geolytics.com 6
. Census. 2008. SF3 Data for Puerto Rico. U.S. Census Bureau, Washington, D.C. www.factfinder.census.gov 7
. HEM3 generally uses the coordinates given by the censu s for the internal point, or “centroid” of each block. How ever, when the footprint of an industrial facility includes the block centroid, the model is designed to identify the highest
- risk point outside of the facility’s footprint.

### 4

each block to the appropriate census statistics. This allowed us to estimate the numbers of people falling into different population subcategories within each block. We then anal yz ed the distribution of estimated inhalation risks within each population subcategory, giving the numbers of people within the subcategory that are exposed to different risk levels. Each distribution involved a tabulation of all the census blocks modeled for the natural gas transmiss i on and storage source category
. W e also computed the average risk for all individuals in each population subcategory
. Distributions of risk and average risks were computed for the raw HEM3 model results for natural gas transmiss i on and storage operations
. For comparison, distributions of risk and average risks were also computed for all emission sources at the facilit y (including natural gas transmiss i on and storage ) (e.g., “ facility
- wide ” ) . A nationwide demographic breakdown (i.e., population percentage in each demographic group for the country as a whole ) is also provided in the results table for comparison
. Section 3.1 describe s the calculation method used for categories where block
- level data were available
-- racial and ethnic categories and the total population. Sections 3.2 through 3.5 describe calculation methods for age categories, education status, household income, and povert y status, respectivel y. 

### 3.1 **Racial and Ethnic Catego rie**  **s and the Total Population** Since race and ethnicit y data were available at the census block level, the calculation of risk distributions for these categories involved a simple block
- by
- block accumulation of the people in each subcategory . We began by identifying a set of bins reflecting the level of risk. The population of each block was then assigned to the appropriate risk bin based on the modeled risk level in the block. The numbers of people in each risk bin were then added together for all of the blocks modeled for the natural gas transmiss i on and storage source category : H(R ab 

### ,s ) = ∑ i (Ra≤Ri<Rb) 

### [ N (s ,i ) ] (1) where: H(R ab 

### ,s ) = the population count for risk bin R ab 

### , which is between R a 

### and R b 

### for population subgroup “s” R i 

### = the modeled risk level in block “í” (estimated lifetime cases of cancer per million population) ∑ i (Ra ≤Ri<Rb) 

### refers to the summation over all blocks i where R i 

### falls in bin R ab 

### , between R a



### and R b 

### N(s ,i ) = the number of people within population subc ategory s , in block i The same approach was used for the total population. The average risk for a given population subcategory or for the total population was calculated using the following equation : A(S) = ∑ i 

### [ N( s ,i ) × R i 

### ] ⁄ ∑ i 

### [ N (s ,i )] (2) where: A(s ) = the average ris k for population subgroup “s” (estimated lifetime cases of cancer

### 5 per million population) ∑ i 

### refers to the summation over all blocks “í” modeled for the emission source categor y N(s ,i) and R i 

### were defined above 

### 3.2 **Age Categories** Age data were retrieved f rom the Table P8 of the census SF3 Table , which contains data on the numbers of males and females of different ages in each census block group. In processing the age data, we began by aggregating the categories in the census to the broader age groups stud ied in this analy sis. For instance, the total number of children 18 ye ars of age and under was calculated b y adding together the number of girls under 1 y ear, the number of boy s under 1 y ear, the number of 1
- ye ar - old girls , the number of 1
- ye ar - old boy s , and so on up to and including 18
- ye ar - old girls and bo ys . In this way , we calculated the number of children age 18 and under, the number of adults from 1 9 to 64, and the number of adults 65 and older in each census block group. The next step was to esti mate the numbers of people in each age group at the block level. To make this calculation , we assumed that the fraction of people in each age group was the same for all blocks in a given block group. Thus, the number of people in a particular age group a nd within a particular census block was estimated as follows: N(a ,b/bg ) = N( t ,b/bg ) × N(a ,bg ) ⁄ N( t ,bg ) (3) where: N(a ,b/bg ) = numb er of people within age group “a” , in block “ b ” of block group “ bg ” N( t ,b/bg ) = total number of people in block “ b ” of block group “ bg ” N(a ,bg ) = numb er of people within age group “a” in block group “ bg ” N( t ,bg ) = total number of people in block group “ bg ” Equation 1 was then applied to the block
- level population estimates to generate risk distributions for different age groups, and Equation 2 was used to compute the average risk for each age group. 

### 3.3 **Level of Education** Table P37 of the SF3 dataset specifies the education status for men and women age 25 and older for each census block group , based on the last grade c ompleted. To obtain the total number of adults without a high school degree, we added together the numbers who had completed grades below a high school senior. Thus, the number of people without a high school degree equals the sum of the number of males with no schooling, the number of females with no schooling, the numbers of males and females who have completed nursery school through 4 th 

### grade, up to the numbers of males and females who have completed some high school but not received a high school degr ee.

### 6

The number of adults without a high school degree as a fraction of the total population was assumed to be the same for each block in the block group. Thus, the number of adults without a high school degree in each block was computed as follows: N ( nhs ,b/bg) = N( t ,b/bg) × N (nhs ,bg ) ⁄ N( t ,bg) (4 ) where: N(nhs ,b/bg) = numb er of adults without a high school diploma, in block “ b ” of block group

“ bg ” N( t ,b/bg) = total number of people in block “ b ” of block group “ bg ” N(nhs ,bg) = numb er of adults without a high school diploma in bloc k group “ bg ” N( t ,bg) = total number of people in block group “ bg ” Equation 1 was then used to generate risk distribution s based on the block
- level results, and Equation 2 was used to compute the average risk for adults without a high school diploma
. 

### 3.4 **Ho usehold Income**  Table P 52 of the SF3 dataset estimates the numbers of households in each block group with income for the ye ar 1999 in various ranges, generall y divided into $5 , 000 increments (e.g. $10,000 to $14,999, $15 , 000 to $19,999, etc.). The median national income for 1999 was about $ 42 ,000 per ye ar. Therefore, in order to determine the number of households with incomes under the median income, we added the estimates for the ranges below that level
. W e assumed that the household incomes in the $40 ,000 to $44,999 increment were evenly distributed over this range. Therefore, 40% of the households in the $40,000 to $4 4 , 999 income range were assumed to be below the national median income of about $42,000. The following equation was used to estimate the fraction of households below the national median income within each census block group: F(sm,bg ) = [C <10 

### + C 10
- 15 

### + .... + C 35
- 40 

### + (0.4×C 40
- 45 

### )] ⁄ C T 

### (5) where: F ( sm ,bg) = fraction of households in block group “bg” with incomes below the median

nati onal income C <10 

### = number of households with incomes under $10,000 C 10
- 15 

### = number of households with incomes from $10,000 to $14,999 C 35
- 40 

### = number of households with incomes from $35,000 to $39,999 C 40
- 45 

### = number of households with incomes from $40 ,000 to $44,999 C T 

### = total number of households in block group “bg” The fraction of people living in households below the median income for each block within the block group was assumed to be the same as the fraction of households below the median incom e for the block group. N(sm, b/bg) = F(sm,bg) × N( t ,b/bg) (6 )

### 7

where: N(sm,b/bg) = number of people in block “b” of block group “bg” living in households below

the national median income F(sm,bg) = fraction of households in block group “bg” below the national median income N( t ,b/bg) = total number of people in block “b” of block group “bg” Equation 1 was then used to generate risk distribution s based on the block
- level results, and Equation 2 was used to compute the average risk for adults without a high school diploma. It must be noted that this approach neglects an y potential relationship between household s ize and income level within a particular block group. However, it is expected to provide a reasonable indication of the risk level of people l iving below the national median income, relative to the population as a whole. 

### 3.5 **Poverty Level** Table P 87 of the SF3 dataset estimates the total number people in each block group living below the povert y level, as well as the numbers of people below the p overty level in different age groups. The current study did not include an analy sis of poverty status by age group, onl y of the total population below the povert y line. The fraction of people below the poverty line was assumed to be the same for each blo ck in the block group. Thus, the population below the poverty line in each block was computed as follows:

N(p ,b/bg) = N(T,b /bg) × N(p ,bg ) ⁄ N(T,bg) (7 ) where: N(p ,b/bg) = number of people below the povert y line in block “b” of block group “bg” N(T,b/bg) = total number of people in block “b” of block group “bg” N(p ,bg) = number of people below the povert y line in block group “bg” N(T,b g) = total number of people in block group “bg” Equation 1 was then used to generate risk distribution s based on the block
- level results, and Equation 2 was used to compute the average risk for adults without a high school diploma. 

# 4. **Results** T he distrib ution of estimated lifetime inhalation cancer risks above 1 in a million for different racial and ethnic groups among the population living near natural gas transmiss i on and storage facilities is shown in Table 2
. For comparison purposes , T able 2 provides the distribution s of inhalation risks for the population exposed to emissions from all source categories at the natural gas transmiss i on and storage facility (i.e., facility
- wide ) ; and Table 2 provides the nationwide percentages of the various demographic groups . D etailed demographic s data and anal ys e s used to create Table 2 can be found in Appendix A of this document.

### 8

The results of the demographic analy sis presented in Table 2 indicate that there are approximately 2,500 people exposed to a cancer ris k greater than or equal to 1
- in
- 1
- million for the natural gas transmiss i on and storage source category
. The demographic results for those impacted b y the source category are below or similar to their corresponding national percentages for all racial, ethn ic and age groups. With respect to those below the poverty level, there is a modest percentage increase (of 4%) compared to the corresponding national percentage (of 13%). Additionally , the “over 25 without a high school diploma” demographic percentage i s higher for those impacted by the source category

(at 20%) than the corresponding national percentage (of 13%) for this demographic. The facility
- wide demographic anal ys is presented in Table 2 indicate s that there are approximately 99,000 people exposed to a cancer risk greater than or equal to 1
- in
- 1
- million resulting from all emissions from these facilities , and that about 42 percent of this population can be classified as minorit y (compared to the national minority percentage of 25%). This higher min ority percentage is attributable to a higher African American demographic percentage (of 40%) compared to the corresponding national percentage (of 12%). In addition, a bout 20 percent of the impacted population is below the povert y l evel, which is 7 perce ntage points higher than the corresponding national percentage for this demographic (of 13%). There is also a modest percentage increase (of 2%) for both the “ages 0 to 18” demographic and the “over 25 without a high school diploma” demographic compared t o the corresponding national percentages for these demographics (of 27% and 13%, respectively). 

# 5. **Uncertainty Discussion** Our anal ys is of the distribution of risks across various demographic groups is subject to uncertainties associated with the extrapol ation of census
- block group data (e.g., income level and education level) down to the census block level. The uncertainties in the risk estimates include the same uncertainties in emissions data sets, in air dispersion modeling, in inhalation exposure and in dose response relationships that are associated with our source category risk estimates. We did not perform tests for statistical significance. It is likel y that most of the differences between source category

and nationwide estimates would be statist ically significant because of the sample sizes of the nationwide data and the people at risk greater than 1 in a million from the source category . However, there may be select cases where the sample size of people at risk greater than 1 in a million is in sufficient to show a statistically significant difference with the nationwide data. The methodology

for our demographic anal ys es is still evolving. While this is our best attempt to provide useful information now, our thinking is continuously advancing . EPA is in the process of developing technical guidance for environmental justice analy ses. We present these anal ys es, with their associated uncertainties, to EPA decision makers and the public as additional anal ys es to inform RTR decisions.

### 9

**Table 2. Summary of Demographic Assessment**  **of Risk Results for the**  **Natural Gas Transmission & Storage**  **Category**

Em issions Basis Dem ographic Group

Total Minority African American Other and

Multiracial Hispanic

or Latino Native

American Ages 0

to 18 Ages 19

to 64 Ages 65

and up Below

the Poverty Level Over 25

Without a HS Diploma Nationwide Dem ographic Breakdow

n n/a 285,339,128 25% 12% 12% 14% 0.9% 27% 60% 12% 13% 13% Maximum Risk (in 1 million) Population With Risk Greater Than or Equal to 1 in 1 million
Source Category 9 0 2,481 8 % 6 % 1 % 1 % 0. 1 % 2 6 % 6 1 % 1 3 % 1 7 % 2 0 % Facility
- wide 2 00 98,891 42 % 40 % 2 % 2 % 0.2 % 29 % 59 % 12 % 20 % 1 5 % Notes: Source Category and Facility
- wide emissions are based on January 201 1 NEI data. Minority population is the total population minus the white population. Population figures are for the population residing within 50 km of these facilities whose cancer risks are estimated to be gr eater than or equal to 1 in a million. There are no hazard indices (HIs) > 1 for the natural gas transmiss i on and storage source category.

### A
- 1 

### Appendi **x A** 

### A
- 2 Tot al popul at ion Wh

it e Afri

can Ameri can Nat ive Ameri can Ot he r and mul ti ra ci al Hisp anic o r La ti no c

0 t o 1 58,363,920 40,536,534 8, 078,975 459,705 9,288,706 10,727,903 1 t o 5 1,937 1,749 160 1 27 28 5 t o 10 435 430 1 1 3 3 10 t o 20 0 0 0 0 0 0 20 t o 30 101 97 0 0 4 0 30 t o 40 0 0 0 0 0 0 40 t o 50 0 0 0 0 0 0 50 t o 100 8 8 0 0 0 0 Tota l numbe r 58,366,401 40,538,818 8, 079,136 459,707 9,288,740 10,727,934 0. 0013 0. 0014 0. 001 0. 0009 0. 0007 0. 0006

0 t o 1 58,267,510 40,481,495 8, 040,021 459,483 9,286,511 10,726,333 1 t o 5 93,709 53,663 37,729 220 2,097 1,538 5 t o 10 4,466 3,285 1, 058 4 119 57 10 t o 20 446 222 216 0 8 5 20 t o 30 116 35 80 0 1 1 30 t o 40 33 8 25 0 0 0 40 t o 50 101 97 0 0 4 0 50 t o 100 14 12 2 0 0 0 100 t o 150 0 0 0 0 0 0 150 t o 200 0 0 0 0 0 0 200 t o 250 6 1 5 0 0 0 Tota l numbe r 58,366,401 40,538,818 8, 079,136 459,707 9,288,740 10,727,934 0. 020 0. 020 0. 028 0. 011 0. 013 0. 012 Note s:

c The Hi sp an ic or Lati no popul at ion is doubl

e-count ed i n th is anal ys is , si nc e dif fe ren t i ndi vi dua ls wi th in t he cat eg or y ma y cl assi fy t he ms el ve s as Whit e,

Afri can Am eri can , Na ti ve Ameri can , or othe r. 

### Ta **bl e**  **A-1 . Di**  **st ri** **but io**  **n of In** **ha la**  **tio n**  **Ca nc**  **er R**  **is k f**  **or R**  **aci al**  **an d**  **Et hni**  **c G ro**  **ups**

a Mode le d ri

sk s are for a 7 0- ye ar l

if et ime, b ased on the predic te d outdoor

co nc en tra ti on and not

ad ju sted for ex pos ur e f actors. Ra nge o f l

if et im e i ndi vi dua l cancer ri sk (chance i n one mi llion) a

Av erag e risk

(c ha nc es i

n one m illion)

b Di stri but ions by race are b ased

on de mogr aphi

c i nf orma ti on at t he cen su s b lo ck

l ev el . R is ks from na tu

ral ga s t ran sm is si on & st or ag e em

is si ons were m

ode le d at t

he b lo ck l evel
. Mode le d ri

sk f rom the natu

ral g as tran sm is si on & st or ag e cat eg or

y

Mode le d ri

sk f rom faci lit ie s co nt ai

ni ng na tu ra l ga s t ra ns mi ssi on & st or ag e sour ce

Av erag e risk

(c ha nc es i

n one m illion) Nu mbe rs o f p eopl

e i n di ffere nt ran ge s fo r l if et ime cancer

ri sk b

### A
- 3 Tota l popul at ion Ag es 0

t hr u 18 Ag es 1 9 thru

64 Ag es 6 5 and

up

0 t o 1 58,363,920 16,459, 946 35,284,060 6,619,914 1 t o 5 1,937 525 1,171 241 5 t o 10 435 105 262 68 10 t o 20 0 0 0 0 20 t o 30 101 17 65 19 30 t o 40 0 0 0 0 40 t o 50 0 0 0 0 50 t o 100 8 2 5 1 Tota l numbe r 58,366,401 16,460, 595 35,285,562 6,620,243 0. 0013 0. 0012 0. 0013 0. 0015

0 t o 1 58,267,510 16,431, 833 35,227,693 6,607,983 1 t o 5 93,709 27, 319 54,847 11,543 5 t o 10 4,466 1, 257 2,585 624 10 t o 20 446 119 274 53 20 t o 30 116 37 66 14 30 t o 40 33 9 20 4 40 t o 50 101 17 65 19 50 t o 100 14 3 9 2 100 t o 150 0 0 0 0 150 t o 200 0 0 0 0 200 t o 250 6 2 4 1 Tota l numbe r 58,366,401 16,460, 595 35,285,562 6,620,243 0. 020 0. 019 0. 020 0. 020 Note s: 

### Ta **bl e**  **A-2 . D**  **is tr**  **ib ut** **io n**  **of R**  **is k f**  **or D**  **iffe re**  **nt**

**A ge**  **G ro**  **ups**

Mode le d ri

sk from the nat

ur al g as t ra ns mi ssi on & st or ag e cat egor

y

b Di stri but ions by ag e ar e b ased

on mode ling da ta at

t he C en su s b lo ck

l ev el , and ag e dat a at the b lo ck g roup le ve l. Al

l bl oc ks i n a b lo ck g roup ar e assu

me d to hav e t he same ag e Ra nge o f l

if et im e i ndi vi dua l cancer ri sk (chance i n one mi llion) a Nu

mbe rs o f p eopl

e i n di ffe re nt range s for l

if et im e cancer ri sk b

Av erag e r is k (c ha nc es i

n one mi llion)

a Mode le d ri

sk s are for a 7 0- ye ar

l if et im e, b ased o n the p red ic te d outdoor

co nc en trati on and not ad ju st ed for ex pos ur e fact or s. Mode le d ri

sk from fa ci lit ie s conta inin

g na tu ral ga s t ra ns mi ssi on & st or ag e so

ur ce cat eg or

y

Av erag e r is k (c ha nc es i

n one mi llion)

### A
- 4 Total popul at io n Tota l numbe r 25 an d ol de r Nu mbe r 2 5 an

d ol de r wi thout a hig h school di pl oma
0 t o 1 58,363,920 36,952,859 8, 189,943 1 t o 5 1, 937 1, 254 364 5 t o 10 435 305 111 10 t o 20 0 0 0 20 t o 30 101 75 16 30 t o 40 0 0 0 40 t o 50 0 0 0 50 t o 100 8 6 2 Total n umbe r 58,366,401 36,954,499 8, 190,436 0. 0013 0. 0013 0. 0015

0 t o 1 58,267,510 36,892,503 8, 175,527 1 t o 5 93,709 58,561 14,196 5 t o 10 4, 466 2, 962 588 10 t o 20 446 294 75 20 t o 30 116 70 23 30 t o 40 33 22 8 40 t o 50 101 75 16 50 t o 100 14 10 3 100 t o 150 0 0 0 150 t o 200 0 0 0 200 t o 250 6 4 1 Total n umbe r 58,366,401 36,954,499 8, 190,436 0. 020 0. 020 0. 019 Notes: 

### Ta **bl e**  **A- 3. D**  **is tr** 

**ib ut**  **io n**  **of R**  **is k for**  **A dul** **ts w**  **ith an**  **d wi**  **th ou** **t a H**  **ig h**  **Sc ho**  **ol**

**D ip**  **lo ma** 

Mode le d ri

sk from the n atu

ra l ga s t ra ns mi ssi on & st or ag e cat eg or

y

b Di st ri but ions b y ed

uc at ion le ve l are b ased

on mode ling da ta at t

he Cen su s b lo ck

l evel , an d ed uc ati on da ta at t he b lo ck g ro up le ve l. Al

l bl oc ks i n a b lo ck g ro up are assu

me d to h av e t he same ed uc at ion le ve l distri

buti on. Ra nge o f l

if et ime i ndi vi dua l cancer ri sk (chan ce i n one m illio n) a Nu

mbe rs o f p eopl

e i n di fferen t ra nge s for l

if et ime cancer ri sk b

Aver ag e r is k (chan

ces i n one mi llion)

a Mode le d ri

sks are fo r a 7 0- ye ar

l if eti me , ba se d on the predic te d out door conc en trati on and not ad justed fo r ex pos ur e f act or s. Mode le d ri

sk from fa ci lit ie s conta inin

g na tura l ga s tran sm is si on & st or ag e sour ce cat eg or y

Aver ag e r is k (chan

ces i n one mi llion)

### A
- 5 Tota l popul at ion Pe opl

e l iving in hous ehol ds b el ow the nationa l me di

an income c Pe opl

e l iving be low the pove rt y line

0 t o 1 58,363,920 29,607,221 8,349,352 1 t o 5 1, 937 1, 242 322 5 t o 10 435 320 93 10 t o 20 0 0 0 20 t o 30 101 58 16 30 t o 40 0 0 0 40 t o 50 0 0 0 50 t o 100 8 6 2 Tota l numbe r 58,366,401 29,608,847 8,349,784 0. 0013 0. 0015 0. 0015

0 t o 1 58,267,510 29,552,048 8,330,279 1 t o 5 93, 709 54, 013 18, 748 5 t o 10 4,466 2, 351 648 10 t o 20 446 254 58 20 t o 30 116 86 25 30 t o 40 33 24 6 40 t o 50 101 58 16 50 t o 100 14 10 3 100 t o 150 0 0 0 150 t o 200 0 0 0 200 t o 250 6 4 1 Tota l numbe r 58,366,401 29,608,847 8,349,784 0. 020 0. 020 0. 020 Note s: **Ta bl**  **e A-4**  **. D is**  **tr**

**ib ut** **io n**  **of Ri**  **sk f**  **or P**  **eo pl**  **e Li** 

**vi ng**  **in H**  **ou seh** **ol ds**  **b el**  **ow**

**t he**  **Na tion**  **al M**  **ed ia**  **n In**  **com**

**e an**  **d Bel**  **ow**

**t he**  **P ove**  **rt**

**y L in**  **e**

Ra nge o f lif

et ime i ndi vi dua l cancer ri sk ( chance i n one mi llion) a Nu

mbe rs o f pe opl

e i n di ffe ren t range s for lif

et ime cancer ri sk b

Av er ag e ri

sk (chances i

n one mi llion)

c The med ia n income i

s t he nationa l me di

an hous ehol d income i n 1999, ab out $42, 000. Mode le d risk

f rom the nat

ur al g as t ra ns missi on & st or ag e cat eg or

y

Av er ag e ri

sk (chances i

n one mi llion)

a Mode le d ri

sk s are for a 7 0- ye ar

l if et ime, b ased on the pre di

ct ed outdoor conc en tra ti on and not ad ju st ed f orex pos ur e factors. b Distri buti ons by income are b ased

on mode lin

g da ta at t he C en su s b lo ck

l evel , an d income dat a at

the b lo ck g roup le ve l. Al

l bl oc ks i n a b lo ck g roup ar e assu

me d to ha ve the sam e i nc ome d is tri buti on. Mode le d risk

f rom fa ci lit ie s conta in

ing na tu ra l ga s tran sm

is si on & st or ag e sour ce cat eg or y