Appendix 9

Technical Support Document: Human Health Multipathway Residual Risk 

Screening Assessment for the Phosphate Fertilizer Production and Phosphoric Acid 

Manufacturing Source Categories
Technical Support Document: Human Health Multipathway Residual 

Risk Screening Assessment for the Phosphate Fertilizers Production 

and Phosphoric Acid Manufacturing Source Categories 

REVISED DRAFT 

July 7, 2014 

Prepared For: 

U.S. Environmental Protection Agency 

Office of Air Quality Planning and Standards 

Research Triangle Park, NC 27711 

Under Contract No. EP-12-010, Work Assignment 2-20 

Prepared By: 

ICF International 

2635 Meridian Pkwy. 

Suite 200 

Durham, NC 27713 
[This page intentionally left blank.]
Human Health Multipathway Residual Risk Screening Assessment for the Phosphate Fertilizers 

Production and Phosphoric Acid Manufacturing Source Categories 

Draft iii July 2014 

CONTENTS

Tables .......................................................................................................................................... iii

Figures ......................................................................................................................................... iv

1. Introduction ........................................................................................................................... 1

2. Tier 1 Emission Screening Assessment ............................................................................... 2

2.1 Tier 1 Emission Screening Results for these Source Categories ................................ 3

3. Tier 2 Emission Screening Assessment ............................................................................... 3

3.1 Adjustment Factors Applied to Tier 1 Screening Values ............................................. 4

3.2 Calculating Refined Tier 2 Fisher Screening Values ................................................... 5

3.3 Finalizing Tier 2 Farmer Screening Values ................................................................. 7

3.4 Tier 2 Screening Results for these Source Categories ............................................... 7

4. Tier 3 Emission Screening Assessment ............................................................................... 9

4.1 Lake Assessment ........................................................................................................ 9

4.2 Tier 3 Lake Assessments Results for these Source Categories ............................... 11

4.3 Plume-rise Assessment ............................................................................................. 12

4.4 Tier 3 Plume-rise Assessment Results for these Source Categories ........................ 13

4.5 Assessment of Time-series Meteorology and Effective Release 

Heights ...................................................................................................................... 14

4.6 Tier 3 Time-series Assessment Results for these Source Categories ...................... 14

5. Comparison to Tier 1 Screening Results for this Source Category .................................... 16

6. References ......................................................................................................................... 18

TABLES 

Table 2-1. Tier 1 Emission Screening Results for these Source Categories ................................ 4

Table 3-1. Tier 2 Screening Results for these Source Categories ................................................ 8

Table 4-1. Results of Tier 3 Lake Assessments for Mercury Emissions ..................................... 11

Table 4-2. Results of Tier 3 Plume-rise Assessments for Mercury Emissions ............................ 13

Table 4-3. Tier 3 SVs Before and After Additional Lake and Plume-rise 

Assessments ........................................................................................................ 14

Table 4-4. Tier 3 Fisher SVs Before and After Time-series Assessments .................................. 16

Table 5-1. Comparison of Tier 1 and Tier 3 Screening Results for these Source 

Categories ............................................................................................................ 17
Human Health Multipathway Residual Risk Screening Assessment for the Phosphate Fertilizers 

Production and Phosphoric Acid Manufacturing Source Categories 

Draft iv July 2014 

FIGURES 

Figure 4-1. Example of Lake Removed from Screening—Likely Evaporated or 

Drained ................................................................................................................. 10

Figure 4-2. Example of Lake Removed from Screening—Likely an Industrial Lake ................... 10

Figure 4-3. Lakes Assessed for NEIMS059305 (Phosphate Fertilizers Production 

Source Category) ................................................................................................. 12

Figure 4-4. The Modeling Spatial Scenario Used for the Unnamed Lake and for 

“Crane Lakes” ....................................................................................................... 15

Figure 4-5. The Modeling Spatial Scenario Used for “Black Creek Cooling Pond” ..................... 15
Human Health Multipathway Residual Risk Screening Assessment for the Phosphate Fertilizers 

Production and Phosphoric Acid Manufacturing Source Categories 

Draft 1 July 2014 

1. Introduction 

This report provides a discussion on a screening-level assessment of human health risks, via 

the ingestion pathway, from exposure to persistent and bioaccumulative hazardous air 

pollutants (PB-HAPs) emitted to the air from phosphate fertilizers production facilities and 

phosphoric acid manufacturing facilities. While this report contains a discussion on some of the 

screening methods, a more detailed discussion on the development, methods, and 

implementation of the screening assessment can be found in Appendix 5 of the Risk Report.1

Where appropriate, this discussion provides references to particular sections of Appendix 5 to 

the Risk Report, where further details on the subject matter can be found. 

Cadmium, dioxins, mercury, and polycyclic aromatic hydrocarbons (PAHs) were the evaluated 

PB-HAP groups,2 selected from a larger list of PB-HAPs based in part on ranking their toxicityweighted air emissions across all source categories. The evaluated exposure scenarios were a 

fisher scenario (i.e., consumption of fish from a lake) and a farmer scenario (i.e., consumption of 

farm food chain [FFC] media such as animal products, fruits and vegetables, and incidental 

ingestion of soil). EPA evaluates the two scenarios together (i.e., the sum of fisher and farmer 

exposures and risks) in the first tier of the assessment, and EPA evaluates them separately in 

the second and third tiers. EPA designed the screening scenarios to be health-protective in 

estimating exposures and risks. Specifically, they are intended to avoid underestimating 

ingestion exposure and risk due to the air emissions of these PB-HAPs from facilities nationwide 

evaluated in the Risk and Technology Review (RTR) program. 

EPA uses the TRIM.FaTE3 model to evaluate the environmental transport, transfer, and fate of 

PB-HAP air emissions. The MIRC4 program then calculates FFC chemical uptake along with 

human exposure, human health cancer risks, and human health non-cancer hazard quotients 

(HQs) resulting from ingestion of fish and FFC media. For screening assessments of 

multipathway risk across the RTR program, EPA used these models with fate and transport 

parameter values, idealized spatial layouts, and generalized meteorology that overall create 

ingestion exposure situations that are unlikely to be exceeded at any actual facility evaluated in 

the RTR program. ICF (hereafter “we”) conducted these model runs to identify threshold 

emission rates (hereafter “thresholds”) that correspond to levels of concern for cancer risks and 

HQs. The levels of concern are incremental, lifetime, human cancer risks of 1-in-one million (for 

PAHs and dioxins) and chronic, non-cancer HQs of 1 (for cadmium and mercury). 

For the iterative (“tiered”) screening-level ingestion assessment described in this report, we 

assessed the potential for ingestion risks above levels of concern in the phosphate fertilizers 

production source category and the phosphoric acid manufacturing source category by 

comparing PB-HAP emissions from facilities within the source categories to the thresholds. We 

use the term “screening values” (SVs) to refer to the ratio of a facility’s emissions of a PB-HAP 

 

1Appendix 5 to the Risk Report is the Technical Support Document for the TRIM-Based Multipathway Tiered 

Screening Methodology for RTR. 

2The phrase “PB-HAP group” is used to distinguish the individual PB-HAP chemicals and congeners from the overall 

family (grouping) of those chemicals. For example, EPA’s ingestion risk methods in its Risk and Technology Review 

(RTR) program evaluate emissions of 17 individual congeners of chlorinated dibenzo-p-dioxins and chlorinated 

dibenzofurans in the “dioxin” PB-HAP group. 

3TRIM.FaTE is the Fate, Transport, and Ecological Exposure module of the Total Risk Integrated Methodology 

modeling system. Additional TRIM.FaTE information can be found at: http://www2.epa.gov/fera/total-risk-integratedmethodology-trim-trimfate. 

4MIRC is the Multimedia Ingestion Risk Calculator. 
Human Health Multipathway Residual Risk Screening Assessment for the Phosphate Fertilizers 

Production and Phosphoric Acid Manufacturing Source Categories 

Draft 2 July 2014 

to that PB-HAP’s threshold. When rounded to one significant figure, an SV of 1 or smaller 

indicates that the emissions did not exceed the threshold and are unlikely to pose health risks 

above levels of concern (i.e., the emissions “screened out”). An SV of 2 or greater indicates that 

the emissions exceeded the threshold and potentially pose health risks above levels of concern. 

The phosphate fertilizers production source category contains 11 facilities, and the phosphoric 

acid manufacturing source category contains 12 facilities. As described in this report, most 

emissions of the evaluated PB-HAPs screened out in the Tier 1 assessment. For the phosphoric 

acid manufacturing source category, one facility’s cadmium and mercury emissions exceeded 

their respective Tier 1 thresholds but screened out in the Tier 2 assessment. For the phosphate 

fertilizers production source category, one facility’s mercury emissions exceeded the Tier 1 

threshold, but the emissions screened out in Tier 3, which included additional assessments of 

its emissions and corresponding meteorology and lake data. 

In Sections 2, 3, and 4, we briefly describe the Tiers 1, 2, and 3 screening methods and discuss 

the results of those screening assessments. We provide in Section 5 a summary comparison of 

the Tier 1 screening results with the screening results after the Tiers 2 and 3 assessments. 

2. Tier 1 Emission Screening Assessment 

The thresholds developed for Tier 1 are intended to apply to any U.S. facility; that is, EPA 

designed them to be applicable to every facility regardless of the facility’s characteristics and 

surrounding environment and the population exposed in its vicinity. The approach to develop the 

thresholds5 assumes ingestion exposure situations that are unlikely to be exceeded at any 

actual facility evaluated in the RTR program. This health-protectiveness is achieved by several 

methods, including (but not limited to): (1) an idealized spatial layout where the evaluated lake 

and farming area are within 2 to 3 km of the emission source and, thus, receive high levels of 

direct deposition; (2) a watershed design where the lake receives substantial indirect chemical 

deposition through large magnitudes of runoff and erosion; (3) a meteorology scenario that 

enhances air concentrations and chemical deposition; and, (4) relatively high ingestion rates 

representing subsistence-level consumption of fish and FFC media. 

Each evaluated PB-HAP group has a single Tier 1 threshold, as shown in Table 3-1 (column e). 

For Tier 1, EPA normalizes the emissions of all dioxin congeners to 2,3,7,8-tetrachlorodibenzop-dioxin-equivalent emissions, and EPA normalizes the emissions of all PAH congeners to 

benzo(a)pyrene-equivalent emissions.6 These normalization factors (i.e., exposure equivalency 

factors [EEFs]) are based on oral toxicity factors and factors related to the congeners’ 

environmental fate and transport characteristics as analyzed in the TRIM.FaTE model.7 For 

mercury, EPA established the threshold for emissions of divalent mercury, although the 

threshold is based on hazards associated with ingestion of methyl mercury from contaminated 

fish (with relatively minimal contribution from ingestion of divalent mercury from FFC media).8 

 

5See Appendix 5 of the Risk Report (Sections 1.1 and 2) for additional information. 

6We sometimes use 2,3,7,8-TCDD and BaP this report as shorthand terms for 2,3,7,8-tetrachlorodibenzo-p-dioxin 

and benzo(a)pyrene, respectively. 

7See Appendix 5 to the Risk Report (Section 2.2.7) for additional information on Tier 1 screening methods. 

8TRIM models mercury transformation in the environment, and exposure in the screening scenario associated with 

ingestion of fish contaminated with methyl mercury (related to emissions of divalent mercury and transformation to 

methyl mercury) results in much larger hazards than exposure associated with ingestion of fish or FFC contaminated 

with divalent mercury. (See Section 2.2 and 2.5.3 in Appendix 5 to the Risk Report.) 
Human Health Multipathway Residual Risk Screening Assessment for the Phosphate Fertilizers 

Production and Phosphoric Acid Manufacturing Source Categories 

Draft 3 July 2014 

2.1 Tier 1 Emission Screening Results for these Source Categories 

As shown in Table 3-1, emissions of dioxins and PAHs (emitted by one facility in the phosphoric 

acid manufacturing source category) screened out because the emissions were approximately a 

factor of 5 below the respective thresholds. 

In the phosphate fertilizers production source category, cadmium emissions screened out. 

Mercury emissions exceeded the threshold by approximately a factor of 20 at one (out of 11) 

mercury-emitting facilities. This facility was NEIMS059305, a Mississippi Phosphates Corp. 

facility in Pascagoula, MS. 

In the phosphoric acid manufacturing source category, cadmium and mercury emissions 

exceeded their respective thresholds by approximately factors of 2 and 7, respectively, at one 

(out of 12) facilities emitting cadmium and mercury. This facility was NEI45571, a PCS 

Phosphates Co. facility in Aurora, NC. PAH and dioxin emissions screened out. When PAH and 

dioxin SVs were summed together per facility (i.e., calculating the total PAH+dioxin screeninglevel potential cancer risk), the highest total “cancer SV” was 0.4 and screened out (not shown 

in table). 

3. Tier 2 Emission Screening Assessment 

The generic site characteristics used in Tier 1 can differ from those actually present at many 

facilities. In Tier 2, EPA takes into account some site-specific characteristics—specifically, 

meteorological conditions and locations of potentially fishable lakes—to apply adjustments to 

the Tier 1 SVs, creating Tier 2 SVs.9 

For a facility undergoing Tier 2 screening, EPA partitions the 50-km area around the facility into 

eight “wedges” or “octants” centered on the facility and compartmentalizing areas north of the 

facility, northeast, east, and so on. As described in Section 3.1, the lake locations and some 

meteorological conditions related to a facility can vary by octant in Tier 2. Though the distance 

from facility to modeled farm remains fixed for each octant, EPA adjusts the location of the 

modeled lake based on actual lake locations. This affects chemical concentrations in some FFC 

media due to modeled erosion and runoff patterns that are directed mostly toward the lake. 

Therefore, for every relevant PB-HAP emitted by a facility, EPA calculates the fisher SV of each 

lake, using the distance from facility to lake and the meteorology conditions of the octant the 

lake is in; and, since lake location can affect the farm SV, EPA calculates a corresponding 

farmer SV for each lake scenario. 

Based on the Tier 2 SVs and other considerations with respect to the source category being 

assessed, EPA might conduct a Tier 3 assessment on some facilities, leading to adjustments to 

the Tier 2 SVs for those facilities. The results we present in Section 3.4 are prior to this Tier 3 

assessment; we discuss the Tier 3 assessment and its effects on SVs in Section 4. 

 

9See Appendix 5 to the Risk Report (Sections 1.2 and 3) for additional information on Tier 2 screening methods. 
Human Health Multipathway Residual Risk Screening Assessment for the Phosphate Fertilizers 

Production and Phosphoric Acid Manufacturing Source Categories 

Draft 4 July 2014 

Table 3-1. Tier 1 Emission Screening Results for these Source Categories 

Source Cat. 

PB-HAP 

Group 

(a) 

Num. Facil. 

Exceeding 

Threshold

(b) 

Largest 

SV 

[(d)/(e)]

(c) 

Facil. with Largest SV 

(d) 

Emiss. at 

Facil. with 

Largest 

SV (TPY)a

(e)

Emiss. 

Screening 

Thresh. 

(TPY) 

Phosphate 

Fertilizers 

Production 

Mercuryb 

(non-cancer)

1 20 NEIMS059305 

(Mississippi Phosphates Corp.; 

Pascagoula, MS) 

6.74E-03 3.16E-04 

Cadmium 

(non-cancer) 

0 0.9 NEIMS059305 

(Mississippi Phosphates Corp.; 

Pascagoula, MS) 

1.11E-02 1.18E-02 

PAHs as BaP 

(cancer) 

N/E N/E N/E N/E 2.58E-03 

Dioxins as 

2,3,7,8-TCDD 

(cancer) 

N/E N/E N/E N/E 2.81E-09 

Phosphoric 

Acid 

Manufacturing 

Mercuryb 

(non-cancer)

1 7 NEI45571 

(PCS Phosphate Co. Inc. - Aurora; 

Aurora, NC)

2.23E-03 3.16E-04 

Cadmium 

(non-cancer) 

1 2 NEI45571 

(PCS Phosphate Co. Inc. - Aurora; 

Aurora, NC)

2.13E-02 1.18E-02 

PAHs as BaP 

(cancer) 

0 0.2 NEI45571 

(PCS Phosphate Co. Inc. - Aurora; 

Aurora, NC)

5.54E-04 2.58E-03 

Dioxins as 

2,3,7,8-TCDD 

(cancer) 

0 0.2 NEI45571 

(PCS Phosphate Co. Inc. - Aurora; 

Aurora, NC)

5.63E-10 2.81E-09 

Notes: N/E = not emitted. TPY = tons per year. SVs rounded to one significant figure. Cell shadings indicate records corresponding 

to SVs of 2 or greater (i.e., the emissions exceeded the threshold). a

We normalized PAH and dioxin emissions in this column to BaP and 2,3,7,8-TCDD, respectively, for oral toxicity and Tier 1 

modeled environmental fate and transport.

b

The emission screening threshold for mercury applies to emissions of divalent mercury, although EPA derived it based on hazards

associated with ingestion of fish contaminated with methyl mercury (i.e., emissions of divalent mercury, which transforms to methyl 

mercury within the environment, accumulates in fish tissue, and is consumed by the fisher). The contribution from hazards 

associated ingestion of divalent mercury from contaminated FFC or fish media is relatively minimal.

3.1 Adjustment Factors Applied to Tier 1 Screening Values 

In developing the adjustment factors used in Tier 2, we conducted hundreds of TRIM.FaTE and 

MIRC model runs corresponding to ranges of meteorological characteristics expected to be 

found at most U.S. locations, and corresponding to lake locations ranging from 2 km to 40 km 

away from the facility. As in Tier 1, the model runs provided emission rates corresponding to risk 

and hazard levels of concern. Because each modeled scenario has different environmental fate 

and transport characteristics, each scenario also has different EEFs to relate PAH and dioxin 

congeners to BaP and 2,3,7,8-TCDD, respectively. Unlike in Tier 1, EPA calculates EEFs and 

thresholds separately in Tier 2 for the fisher and farmer scenarios. The Tier 2 adjustment factors 

are the ratios of the Tier 2 EEFs and thresholds to those of Tier 1. EPA applies the Tier 2 

adjustment factors to Tier 1 SVs in order to calculate Tier 2 fisher SVs and Tier 2 farmer SVs. 

We discuss below an additional adjustment factor based on wind direction. 

In order to match an assessed facility in Tier 2 with its appropriate meteorology- and lakerelated Tier 2 adjustment factors, EPA matches the facility with the same meteorology station to 
Human Health Multipathway Residual Risk Screening Assessment for the Phosphate Fertilizers 

Production and Phosphoric Acid Manufacturing Source Categories 

Draft 5 July 2014 

which it is matched in the RTR inhalation risk assessment (i.e., typically the closest station), and 

EPA also identifies qualifying lakes around the facility. Some of a facility’s meteorology patterns 

vary by octant, and qualifying lakes (discussed below) can be scattered around multiple octants 

and at multiple distances from the facility. Therefore, for each lake in each octant around a 

facility, EPA matches its combination of meteorology data and lake distance to its appropriate 

scenario in the Tier 2 model runs and, thus, to the appropriate Tier 2 adjustment factors. 

EPA bases the meteorology data used in Tier 2 on the same dataset used in RTR inhalation risk 

assessments, consisting of more than 800 meteorology stations nationwide. We processed 

hourly data from the meteorology stations to derive typical or total station-specific values of wind 

speed, wind direction, mixing height, and precipitation. For each station, we then matched the 

combination of these values with the most representative meteorological scenario used in the 

Tier 2 model runs. The matching method is health-protective (i.e., wind speeds and mixing 

heights match to their closest, smaller value in the Tier 2 model runs, and a precipitation value 

to its closest, larger value). We also calculated the frequency of winds blowing toward each of 

the octants around each station. EPA compares the frequency of winds blowing into an octant to 

the frequency used in Tier 1, creating a Tier 2 wind frequency adjustment factor. 

EPA analyzes all qualifying lakes within 50 km of the facility. A qualifying lake (1) is at least 25 

acres in surface area but no larger than 100,000 acres;10 (2) is classified by USGS as a lake or 

reservoir but not used for disposal, treatment, or evaporator purposes; (3) does not have a 

name suggesting it is not intended for public use (e.g., “Gavin Fly Ash Impoundment”); and, (4) 

has not been removed in previous source category assessments based on these and other 

inspection methods. EPA assigns each lake to its respective octant around the assessed facility 

and to the closest lake distance value used in the Tier 2 model runs, where the matching 

method is health-protective (i.e., a lake’s distance matches to its closest, smaller value in the 

Tier 2 model runs). In cases where there are no qualifying lakes around the facility, there is no 

exposure or risk to the fisher. 

The Tier 2 fisher and farmer SVs calculated at this point in the assessment are “initial SVs”; this 

is because subsequent steps in Tier 2 refine the fisher SVs (see Section 3.2) and select one of 

the potentially many farmer SVs (see Section 3.3). 

3.2 Calculating Refined Tier 2 Fisher Screening Values 

The subsistence fisher in Tier 1 consumes fish from one lake at the subsistence ingestion rates, 

regardless of the lake’s ability to support a fish population that allows for that level of 

consumption across many years. In Tier 2, EPA considers the lake’s capacity to accommodate 

the assumed fish ingestion rates. For any particular lake, the fisher in Tier 2 catches and 

consumes fish from that lake at an amount proportional to the area of the lake, which serves as 

an approximation of the lake’s biological productivity.11 In order to consume fish at the ingestion 

rate used in Tier 2, the fisher might need to fish multiple lakes (and be exposed to several 

different chemical concentration levels in fish). 

The initial Tier 2 fisher SVs and the Tier 1 fisher SVs use a fixed set of fish ingestion rates 

covering a range of ages. The highest fish ingestion rate among the age groups is 373 g fish/d 

for adults, which for simplicity EPA uses to estimate a lake’s capacity to support subsistence 

fishing. Smaller lakes are unlikely to support this level of fish consumption over time (i.e., the 

 

10Discussed further in Appendix 5 (Section 3 and Attachment E) to the Risk Report. 

11See Appendix 5 to the Risk Report (Section 3 and Attachment E) for additional information on lake productivity. 
Human Health Multipathway Residual Risk Screening Assessment for the Phosphate Fertilizers 

Production and Phosphoric Acid Manufacturing Source Categories 

Draft 6 July 2014 

lake would be “fished out”), although the fisher could catch and consume that amount of fish 

collectively from multiple small lakes. In Tier 2, EPA assumes that a fisher can catch and 

consume no more than 1 g fish/d/acre lake without impacting the lake’s long-term sustainability. 

In order to reach the assumed ingestion rate, EPA assumes that the fisher catches and 

consumes fish from one or more lakes until he is able to fish a total of 373 acres of lake and 

consume a total of 373 g fish/d (i.e., the screening scenario adult fish ingestion rate) or until 

there are no more qualifying lakes to fish to reach 373 total acres. 

EPA uses the initial Tier 2 fisher SVs calculated for all qualifying lakes around a facility, along 

with the acreage values of those lakes, to identify which lake(s) the fisher catches and 

consumes fish from and the amount of fish caught from each lake. Using this information, EPA 

refines the Tier 2 fisher SV based on a scenario assuming consumption of fish from multiple 

lakes. EPA conducts the steps below for each PB-HAP group emitted by a facility. 

1. Identify the lake with the highest chemical concentration in fish12 for a given PB-HAP group, 

according to the initial Tier 2 fisher SVs. 

2. If the lake with the highest concentration is at least 373 acres in area, then the fisher 

consumes fish from only that lake, at the subsistence-level ingestion rates (the adult rate 

being 373 g fish/d). That is, the refined Tier 2 fisher SV equals the initial Tier 2 fisher SV. 

3. If the lake with the highest concentration is smaller than 373 acres, then the fisher catches 

only the amount of fish consistent with the assumption of 1 g fish/d/acre lake. That is, 

multiply the initial Tier 2 fisher SV for that lake by [its acreage]÷[373 acres]; put another way, 

multiply the SV by [the daily mass of fish consumed from the lake]÷[373 g fish/d]. Apply the 

following logic to subsequent lakes. 

a. The fisher catches and consumes fish from one or more additional lakes, in order 

of highest to lowest concentration. If multiple lakes have the same concentration, 

then he fishes them in order of largest to smallest acreage. He stops fishing 

when he fishes lakes totaling 373 acres or when there are no more qualifying 

lakes to fish to reach 373 total acres. Scale each additional lake’s initial Tier 2 

fisher SV by acreage (i.e., by fish consumption rate) in the same way as the first 

fished lake (see above). 

b. If the cumulative area of all qualifying lakes is smaller than 373 acres (i.e., if all 

lakes together cannot support a 373 g fish/d adult ingestion rate, assuming 1 g 

fish/d/acre lake), then the fisher does not consume the full 373 g fish/d. 

c. If the cumulative area of all qualifying lakes is larger than 373 acres, the fisher 

consumes only the amount of fish from the final lake necessary to reach 373 g 

fish/day. That is, scale the initial Tier 2 fisher SV for that lake by [the remaining 

acreage necessary to reach 373 acres, after fishing the prior lake(s)]÷[373 

acres]. 

d. The refined Tier 2 fisher SV (reflecting the refined fisher methods) is the sum of 

the adjusted Tier 2 fisher SVs of all fished lakes as calculated above. 

 

12In the screening assessments, for a given ingestion rate, SVs are directly and proportionally related to chemical 

concentrations in the exposure media. For simplicity and to more clearly relate the potential health impacts of 

consuming a lake’s fish to the chemical concentrations in those fish, EPA discusses fish concentrations in describing 

the methods of calculating the refined Tier 2 angler SVs. 
Human Health Multipathway Residual Risk Screening Assessment for the Phosphate Fertilizers 

Production and Phosphoric Acid Manufacturing Source Categories 

Draft 7 July 2014 

3.3 Finalizing Tier 2 Farmer Screening Values 

For a given PB-HAP group emitted by a facility, EPA identifies the largest Tier 2 farmer SV from 

all the relevant meteorology and lake-distance scenarios. This helps to avoid underestimating 

exposure and risk. 

3.4 Tier 2 Screening Results for these Source Categories 

In this section, we discuss the Tier 2 screening results. The results in this section use the 

refined Tier 2 fisher SVs (discussed in Section 3.2) and the largest Tier 2 farmer SVs (discussed 

in Section 3.3). 

As shown in Table 3-2, all emissions screened out except for mercury emissions from 

NEIMS059305 (phosphate fertilizers production source category). The fisher SV at that facility 

was 3, while the farmer SV was 0.002. Mercury and cadmium emissions from NEI45571 

(phosphoric acid production source category), which exceeded their respective Tier 1 thresholds 

by factors of 7 and 2, screened out in Tier 2—its mercury and cadmium Tier 2 fisher SVs were 1 

and 0.3, respectively, and the Tier 2 farmer SVs were 0.0007 and 0.02, respectively. 

When PAH and dioxin SVs were summed together per facility in the phosphoric acid 

manufacturing source category (i.e., calculating the total PAH+dioxin screening-level potential 

cancer risk), the highest total “cancer SVs” screened out (SV = 0.04 for fisher, 0.07 for farmer; 

not shown in table). 
Human Health Multipathway Residual Risk Screening Assessment for the Phosphate Fertilizers 

Production and Phosphoric Acid Manufacturing Source Categories 

Draft 8 

Table 3-2. Tier 2 Screening Results for these Source Categories 

Facil. Type 

PB-HAP 

Group 

Num. Facil. 

Exceeding 

Fisher 

Threshold

Num. Facil. 

Exceeding 

Farmer 

Threshold 

Num. Facil. Exceeding 

Threshold, 

Either Fisher or Farmer,

Both Fisher and Farmer

Largest 

Fisher SV 

Largest 

Farmer 

SV 

Facil. with Largest 

Fisher SV 

Phosphate Fertilizers Production 

Mercurya (non-cancer)

1 1 1 

0 

3 0.002 NEIMS059305 

(Mississippi Phosphates Corp.; Pascagoula, MS)

Cadmium (non-cancer) 

0 0 0 

0 

0.1 0.008 NEIMS059305 

(Mississippi Phosphates Corp.; Pascagoula, MS)

PAHs as BaP (cancer) 

N/E N/E N/E N/E N/E N/E 

Dioxins as 2,3,7,8-TCDD (cancer) 

N/E N/E N/E N/E N/E N/E 

Phosphoric Acid Manufacturing 

Mercurya (non-cancer)

0 0 0 

0 

1 0.0007 NEI45571 

(PCS Phosphate Co. Inc. - Aurora; Aurora, NC)

Cadmium (non-cancer) 

0 0 0 

0 

0.3 0.02 NEI45571 

(PCS Phosphate Co. Inc. - Aurora; Aurora, NC)

PAHs as BaP (cancer) 

0 0 0 

0 

0.01 0.06 NEI45571 

(PCS Phosphate Co. Inc. - Aurora; Aurora, NC)

Dioxins as 2,3,7,8-TCDD (cancer) 

0 0 0 

0 

0.03 0.01 NEI45571 

(PCS Phosphate Co. Inc. - Aurora; Aurora, NC)

Notes: N/E = not emitted. TPY = tons per year. SVs rounded to one significant figure. Cell shadings indicate records corresponding to SVs of 2 or greater 

the threshold). Emissions and screening thresholds not shown for space purposes. 

aThe emission screening threshold for mercury applies to emissions of divalent mercury, although EPA derived it based on hazards associated with inges

methyl mercury (i.e., emissions of divalent mercury, which transforms to methyl mercury within the environment, accumulates in fish tissue, and is consum

contribution from hazards associated ingestion of divalent mercury from contaminated FFC or fish media is relatively minimal.
Human Health Multipathway Residual Risk Screening Assessment for the Phosphate Fertilizers 

Production and Phosphoric Acid Manufacturing Source Categories 

Draft 9 July 2014 

4. Tier 3 Emission Screening Assessment 

Based on the Tier 2 SVs and other considerations with respect to the source category being 

assessed, EPA may conduct Tier 3 assessments on some facilities. We discuss in this section 

the Tier 3 assessment conducted for mercury hazards for NEIMS059305 in the phosphate 

fertilizers production source category, whose Tier 2 fisher SV for mercury was 3. 

4.1 Lake Assessment 

Other than verifying a facility’s emission rates, one of the simplest assessments EPA can 

conduct (beyond the Tier 2 methods) is assessing the existence, the potential purpose, the 

accessibility and fishability, and the suitability of lakes for the models and methods used in Tier 

2. The full USGS dataset of lakes and reservoirs nationwide that EPA uses in Tier 2 does not 

contain information on lake accessibility or fishability. In addition, it occasionally identifies a lake 

that no longer exists (e.g., it has evaporated or been drained) or it uses a classification that 

might not accurately reflect the lake’s purpose or type. EPA uses aerial and street-view imagery 

and internet searches to quickly ascertain if an assessed lake actually exists, if it is probably not 

fished (e.g., appears swampy or covered in algae), if it is likely used for industrial or waste 

disposal/treatment purposes, and/or if it is adjacent to or connected to a river or saltwater body 

(estuaries, rivers, and saltwater areas are not ideal for the assessment models and methods). 

For example, the blue outline in Figure 4-1 identifies a lake from the USGS dataset that 

originally qualified for Tier 2 based on the information provided in that dataset, but aerial 

imagery shows it is likely evaporated or drained. Similarly, the outline in Figure 4-2 identifies a 

lake that originally qualified, but aerial imagery shows that it is directly adjacent to an industrial 

facility and likely used only for on-site industrial purposes. 

For facilities undergoing Tier 3 screening, EPA evaluates all lakes from which the fish catches 

and consumes fish according to the refined Tier 2 fisher methods discussed in Section 3.2. EPA 

permanently removes, from the screening assessment, all lakes meeting the criteria discussed 

in the previous paragraphs, so that they are no longer used in any screening assessment. If 

EPA removes a lake from the facility’s assessment, it might be necessary for the hypothetical 

fisher to catch and consume fish from additional lake(s) in order to fish a total of 373 acres. In 

this case, EPA evaluates additional lakes that were not fished, using the methods discussed in 

Section 3.2, in descending order of initial Tier 2 fisher SV and lake area. 

If EPA removes any lakes from the screening, EPA conducts the screening again (using the Tier 

2 methods) with the revised lake dataset. Although EPA conducts this additional lake 

assessment based on the Tier 2 SVs of a particular set of facilities, lakes removed during that 

assessment could affect the SVs of other facilities in the source category beyond that original 

set. This can happen if an assessed facility is within 50 km of another assessed facility, whereby 

removing a lake could affect the SVs of both facilities. EPA does not sum SVs across facilities. 
Human Health Multipathway Residual Risk Screening Assessment for the Phosphate Fertilizers 

Production and Phosphoric Acid Manufacturing Source Categories 

Draft 10 July 2014 

Figure 4-1. Example of Lake 

Removed from Screening—Likely 

Evaporated or Drained 

Note: Aerial imagery from ESRI World Imagery (2014). 

 

 Figure 4-2. Example of Lake Removed from Screening—Likely an 

Industrial Lake 

Note: Aerial imagery from ESRI World Imagery (2014). 
Human Health Multipathway Residual Risk Screening Assessment for the Phosphate Fertilizers 

Production and Phosphoric Acid Manufacturing Source Categories 

Draft 11 July 2014 

4.2 Tier 3 Lake Assessments Results for these Source Categories 

The information in Table 4-1 is related to the lakes evaluated in the screening of NEIMS059305 

in the phosphate fertilizers production source category. The table includes one lake we removed 

during the assessment (see gray shaded row). For lakes remaining in the screening after the 

lake assessment, the table contains information on how much of the subsistence fisher’s daily 

fish consumption came from each lake, and how much of the corresponding fisher SV was 

attributable to each lake. 

Table 4-1. Results of Tier 3 Lake Assessments for Mercury Emissions 

Facil. NEI ID Lake Name 

Lake 

Area 

(acres) 

Selection 

Order 

Percent 

of 

Ingested 

Fish 

Coming 

From 

This Lake 

Percent of 

Tier 3 

Fisher SV 

Attributed 

To This 

Lake 

Reason for 

Removal 

NEIMS059305 

(phosphate 

fertilizers 

production source 

category) 

Name Not Provided 49 1 9% 16% -- 

Crane Lakes 82 2 10% 14% -- 

Black Creek Cooling 

Ponda

59 3 81% 70% -- 

Presley Pond 30 RMV-1 -- -- Evaporated 

or drained 

Notes: 

The lakes shown in this table, and their corresponding selection order and percentages of ingestion and SV, are related only to the 

mercury emissions from this facility. For other PB-HAP groups emitted by this facility, the fisher might fish a different set of lakes 

and/or with a different selection order. 

“RMV” indicates that we removed the lake during Tier 3. The number beside the “RMV” designation was for map labeling purposes 

(see the figure in this subsection). The percentages of ingestion and SV reflect the assessment after we removed this lake. a

Black Creek Cooling Pond appears to have been created by a dam and, despite its name, we found no reliable information 

suggesting it is restricted access, unfishable, or industrial. 

Figure 4-3 is an aerial image delineating the lakes in Table 4-1. The labels of the lakes in the 

map correspond to the data in the “Selection Order” column of the table. Lakes labeled in the 

map with negative numbers (e.g., -1, -2, and so on) are qualifying lakes that the fisher did not 

fish because the fish ingestion rate was already met by fishing the first set of lakes (i.e., by 

fishing those labeled 1, 2, and so on). The map is focused on the fished and removed lakes, so 

it does not show all unfished lakes. Table 4-1, for space purposes, does not contain information 

on these unfished lakes. NEIMS059305 is close to the Gulf of Mexico and has many water 

bodies of varying types within 50 km; the red outlines and text in the map call attention to water 

bodies within the map extent that did not qualify for the Tier 2 because they appeared to be 

estuarine. 

As discussed in Section 3.4, this facility’s mercury emissions exceeded the Tier 2 thresholds for 

fishers by approximately a factor of 3. Removing one lake from this facility’s screening did not 

effectively decrease its Tier 3 fisher SV, so we conducted a plume-rise assessment on the 

mercury emissions, as discussed in Sections 4.3 and 4.4. 
Human Health Multipathway Residual Risk Screening Assessment for the Phosphate Fertilizers 

Production and Phosphoric Acid Manufacturing Source Categories 

Draft 12 July 2014 

 Figure 4-3. Lakes Assessed for NEIMS059305 

(Phosphate Fertilizers Production Source 

Category) 

Notes: Aerial imagery from ESRI (2014). Lake labels correspond to the 

“Selection Order” column in Table 4-1. The “lake” shown in Figure 4-1 

corresponds to “RMV-1” here. 

4.3 Plume-rise Assessment 

In Tiers 1 and 2, all chemicals are emitted inside the mixing layer and are available for groundlevel exposure. In reality, the physical height of an emission source, in combination with the 

temperature and velocity of the chemical plume as it leaves the source, can cause some of the 

chemical plume to reach areas above the mixing layer. In TRIM.FaTE modeling, the chemical 

mass deposited above the mixing layer (i.e., the model’s upper-air layer) is unavailable for 

ground-level exposure (i.e., the upper-air layer functions as a chemical sink). Many emission 

sources in RTR are physically taller than the mixing height during some hours, and hot exit gas 

temperatures (i.e., buoyancy) and/or high exit gas velocities (i.e., momentum) can further 

elevate the chemical plume. 

EPA uses methods summarized by Seinfeld and Pandis (1998) to estimate how often a facility’s 

emissions reach the upper-air sink, which decreases availability for ground-level exposure. The 

methods to estimate the amount of chemical lost to the upper-air sink require use of the facility’s 
Human Health Multipathway Residual Risk Screening Assessment for the Phosphate Fertilizers 

Production and Phosphoric Acid Manufacturing Source Categories 

Draft 13 July 2014 

corresponding meteorology data (e.g., air temperature and vertical temperature gradient, wind 

speed, and atmospheric stability), the mass of the PB-HAP emitted from each source, the 

physical characteristics of the sources (i.e., release height, inside diameter at the release point, 

and exit gas temperature and velocity), and an estimate of the size of the facility. 

For each relevant emission source, EPA estimates the hourly effective release height (i.e., sum 

of actual release height and plume rise) and compares it to the hourly mixing height to 

determine the mass of chemical remaining in the mixing layer. EPA compares the mass of 

chemical remaining in the mixing layer, summed across the sources, to the total emitted mass 

of the chemical. This results in an adjustment factor expressing the fraction of emissions 

remaining in the mixing layer after accounting for release height and plume rise. EPA applies 

this final plume-rise adjustment factor to the Tier 2 SVs. 

4.4 Tier 3 Plume-rise Assessment Results for these Source Categories 

The Tier 3 lake assessment did not effectively lower the Tier 3 fisher SV for mercury emissions 

from NEIMS059305 (phosphate fertilizers production source category; see Section 4.2). We 

also conducted a plume-rise assessment on the emissions. Table 4-2 contains information on 

the mercury emissions and physical characteristics of each unique emission source, along with 

the fraction of mercury emitted from each source that remained in the mixing layer (i.e., is not 

deposited into the upper-air sink). We show in the last column the total fraction of emissions 

from all sources together that remained in the mixing layer. We calculated this value by 

weighting the value in the previous column (fraction remaining in the mixing layer, by source) by 

the fraction of mercury emissions coming from each source (i.e., the third column), and 

summing those weighted values. To account for these plume-rise data, we scaled the Tier 2 

fisher and farmer SVs by the fractions shown in the last column. 

Table 4-2. Results of Tier 3 Plume-rise Assessments for Mercury Emissions 

Facil. NEI ID 

Source 

Num. 

Fraction of 

Emiss. 

From This 

Source 

Physical Characteristics of Emiss. 

Source 

Fraction of Emiss.

Remaining in 

Mixing Layer 

Height 

(m) 

Exit 

Gas 

Temp. 

(K) 

Inside 

Diameter 

(m) 

Exit 

Gas 

Vel. 

(m/s) 

By 

Source 

Facility 

Total 

NEIMS059305 

(phosphate 

fertilizers production 

source category) 

1 0.0121 24.7 350 1.8 13.1 0.806 0.7679

2 0.9879 48.8 355 1.8 12.5 0.7675 

Table 4-3 contains the previously calculated Tier 2 SVs for mercury (reflecting the assessment 

described in Section 3), along with the SVs after the Tier 3 lake and plume-rise assessments, 

for NEIMS059305 (phosphate fertilizers production source category). 

While the Tier 3 lake assessments alone did not effectively decrease the SVs, the combined 

effect of the lake and plume-rise assessments was a decrease in the SVs from 3 to 2 for the 

fisher scenario, and from 0.002 to 0.001 for the farmer scenario. The mercury emissions still 

exceeded the threshold for the fisher scenario. These assessments did not impact SVs at any 

other facilities in the phosphate fertilizers production or phosphoric acid manufacturing source 

categories. We discuss in Sections 4.5 and 4.6 an additional assessment that we conducted on 

the emissions using time-series meteorology and release-height data. 
Human Health Multipathway Residual Risk Screening Assessment for the Phosphate Fertilizers 

Production and Phosphoric Acid Manufacturing Source Categories 

Draft 14 July 2014 

Table 4-3. Tier 3 SVs Before and After Additional Lake and Plume-rise Assessments 

Facil. NEI ID 

Facil. 

Name Facil. City 

Facil

. 

State

Tier 2 and Tier 3 Mercury SVa

Before Tier 3 

Assessments 

After Tier 3 

Lake 

Assessments 

After Tier 3

Lake AND 

Plume-rise 

Assessments 

Fisher 

Farme

r 

Fishe

r 

Farme

r 

Fishe

r 

Farme

r 

NEIMS059305 

(phosphate 

fertilizers production 

source category) 

Mississippi 

Phosphate

s Corp. 

Pascagoula MS 3 0.002 3 0.002 2 0.001

a

SVs rounded to one significant figure. Cell shadings indicate SVs of 2 or greater (i.e., the emissions exceeded the threshold).

4.5 Assessment of Time-series Meteorology and Effective Release Heights 

As discussed in Section 3, EPA bases the Tier 2 SVs on the average meteorological conditions 

prevailing at the facility being assessed. The use of time-series meteorology data, which 

captures hour-by-hour changes in each of the assessed meteorological parameters instead of 

using constant average values, increases the accuracy of the estimates of potential risk by 

accounting for potential statistical interactions between the meteorology parameters and by 

improving the method of accounting for mass advected into the modeling domain. 

EPA also bases Tier 2 SVs on a constant emission release height that is always within the 

mixing layer. Including hourly effective release heights (discussed in Sections 4.3 and 4.4) along 

with hourly meteorology data further increases the accuracy of the estimates of potential risk. 

For a facility undergoing a time-series assessment, EPA develops a time series of hourly 

effective release heights for sources emitting the assessed PB-HAP, and EPA identifies the Tier 

2 spatial scenario that best matches each lake from which the hypothetical fisher catches and 

consumes fish. Using this data along with the facility’s matching hourly meteorology data, the 

facility’s emission rates, and the subsistence ingestion rates, EPA models chemical fate and 

transport in TRIM.FaTE and calculates the corresponding screening-level risks using MIRC. 

This modeling results in a screening-level risk value for each lake, corresponding to ingestion of 

fish exposed to the evaluated PB-HAP. If the farmer scenario is specifically being assessed, the 

modeling will also result in a screening-level risk value for each farm. EPA multiplies the 

screening-level risk associated with each lake by the percent of daily ingested fish caught from 

the lake (see Sections 3.2 and 4.2); summing those products across all modeled lakes results in 

the screening-level fisher risk (i.e., fisher SV) associated with the evaluated PB-HAP emitted by 

the facility. The time-series-adjusted Tier 3 SVs are compared to the Tier 2 SVs calculated 

previously. 

4.6 Tier 3 Time-series Assessment Results for these Source Categories 

In order to account for the potential effects on exposure and risk modeling from using timeseries meteorology and effective release heights in TRIM.FaTE, we ran TRIM.FaTE three times, 

corresponding to each of the three assessed lakes for the mercury assessment for 

NEIMS059305 (phosphate fertilizers production source category). We used the “lake at 10 km” 

spatial scenario, shown in Figure 4-4, to model concentrations in the unnamed lake and Crane 

Lakes (see Table 4-1). In reality, these two lakes were respectively 12 and 19 km from the 

facility. We used the “lake at 20 km” spatial scenario, shown in Figure 4-5, to model 

concentrations in Black Creek Cooling Pond (see Table 4-1), which in reality was 23 km from 

the facility. 
Human Health Multipathway Residual Risk Screening Assessment for the Phosphate Fertilizers 

Production and Phosphoric Acid Manufacturing Source Categories 

Draft 15 July 2014 

 Figure 4-4. The Modeling Spatial Scenario Used for the 

Unnamed Lake and for “Crane Lakes” 

Notes: Labels = surface parcel names for modeling. Shadings = ground cover type for 

modeling. Arrows within scenario = direction of runoff and erosion. 

Figure 4-5. The Modeling Spatial Scenario Used for “Black 

Creek Cooling Pond” 

Notes: Labels = surface parcel names for modeling. Shadings = ground cover type for 

modeling. Arrows within scenario = direction of runoff and erosion.
Human Health Multipathway Residual Risk Screening Assessment for the Phosphate Fertilizers 

Production and Phosphoric Acid Manufacturing Source Categories 

Draft 16 July 2014 

Table 4-4 contains the Tier 3 fisher SVs for mercury emissions from NEIMS059305 (phosphate 

fertilizers production source category), both before and after the time-series assessments. Both 

SVs reflect the Tier 3 lake assessments (see Section 4.2) but not the plume-rise assessments 

(see Section 4.4); this is because the time-series assessment includes chemical loss due to 

plume rise into the upper-air sink. Beside the previous results, the table contains the fisher SV 

after the time-series assessments. We did not assess farmer SVs with these time-series runs. 

The time-series assessments decreased the fisher SV to below levels of concern (i.e., the 

emissions screened out). 

Table 4-4. Tier 3 Fisher SVs Before and After Time-series Assessments 

Facil. NEI ID 

Facil. 

Name Facil. City 

Facil. 

State 

Tier 3 Mercury Fisher SVa

Before Tier 3 Timeseries Assessments After Tier 3 Timeseries Assessments 

NEIMS059305 

(phosphate fertilizers 

production source 

category) 

Mississippi 

Phosphates 

Corp. 

Pascagoula MS 3 1 

a

SVs rounded to one significant figure. Cell shadings indicate SVs of 2 or greater (i.e., the emissions exceeded the threshold). We 

only assessed the fisher scenario during the time-series assessments. 

5. Comparison to Tier 1 Screening Results for this Source Category 

In Table 5-1, we present a high-level comparison between the Tier 1 SVs and Tier 3 SVs. The 

Tier 3 SVs reflect the Tier 3 screening of mercury emissions from one facility; otherwise, the 

Tier 3 SVs are unchanged from the Tier 2 screening. The remainder of this section provides an 

overview of the results for each of the four PB-HAPs. 

 Mercury: 

– Emissions at one facility in each source category exceeded the Tier 1 threshold but 

screened out in Tier 3. 

– The largest Tier 3 fisher and farmer SVs were respectively approximately 20 times 

and 20,000 times smaller than the largest Tier 1 SV (which combined fish- and FFCrelated exposure). 

– When the largest Tier 3 fisher SV was combined with the largest Tier 3 farmer SV (to 

directly compare to the largest Tier 1 SV), the combined Tier 3 SV was approximately 

20 times smaller (not shown in the table). This is because nearly all mercury 

exposure occurs through fish ingestion. 

 Cadmium: 

– Emissions at one phosphoric acid manufacturing facility exceeded the Tier 1 

threshold but screened out in Tier 3. 

– The largest Tier 3 fisher and farmer SVs were respectively approximately nine times 

and 100 times smaller than the largest Tier 1 SV (which combined fish- and FFCrelated exposure). 

– When the largest Tier 3 fisher SV was combined with the largest Tier 3 farmer SV (to 

directly compare to the largest Tier 1 SV), the combined Tier 3 SV was approximately 

three times smaller than the Tier 1 SV (not shown in the table). This is because nearly 

all cadmium exposure occurs through fish ingestion. 
Human Health Multipathway Residual Risk Screening Assessment for the Phosphate Fertilizers 

Production and Phosphoric Acid Manufacturing Source Categories 

Draft 17 July 2014 

 PAHs: 

– All emissions screened out. 

– The largest Tier 3 fisher and farmer SVs were respectively approximately 20 times 

and three times smaller than the largest Tier 1 SV (which combined fish- and FFCrelated exposure). 

– When the largest Tier 3 fisher SV was combined with the largest Tier 3 farmer SV (to 

directly compare to the largest Tier 1 SV), the combined Tier 3 SV was approximately 

three times smaller than the largest Tier 1 SV (not shown in the table). 

 Dioxins: 

– All emissions screened out. 

– The largest Tier 3 fisher and farmer SVs were respectively approximately seven times 

and 20 times smaller than the largest Tier 1 SV (which combined fish- and FFCrelated exposure). 

– When the largest Tier 3 fisher SV was combined with the largest Tier 3 farmer SV (to 

directly compare to the largest Tier 1 SV), the combined Tier 3 SV was approximately 

five times smaller than the largest Tier 1 SV (not shown in the table). 

 PAHs + Dioxins: 

– The facility-level sum of PAH and dioxin SVs screened out in all screening 

assessments (not shown in table). 

Table 5-1. Comparison of Tier 1 and Tier 3 Screening Results for these Source Categories 

Source Cat. 

PB-HAP 

Group 

Num. Facil. Exceeding Threshold Largest SV 

Tier 1, Combined 

Fisher and Farmer 

Tier 3, 

Fisher

Tier 3, 

Farmer

Tier 1, Combined 

Fisher and Farmer 

Tier 3, 

Fisher

Tier 3, 

Farmer

Phosphate 

Fertilizers 

Production 

Mercurya 

(non-cancer)

1 0 0 20 1 0.001 

Cadmium 

(non-cancer) 

0 0 0 0.9 0.1 0.008 

PAHs as BaP 

(cancer) 

N/E N/E N/E N/E N/E N/E 

Dioxins as 

2,3,7,8-TCDD 

(cancer) 

N/E N/E N/E N/E N/E N/E 

Phosphoric 

Acid 

Manufacturing 

Mercurya 

(non-cancer)

1 N/E N/E 7 1 0.0007 

Cadmium 

(non-cancer) 

1 N/E N/E 2 0.3 0.02 

PAHs as BaP 

(cancer) 

0 0 0 0.2 0.01 0.06 

Dioxins as 

2,3,7,8-TCDD 

(cancer) 

0 0 0 0.2 0.03 0.01 

Notes: N/E = not emitted. SVs rounded to one significant figure. Cell shadings indicate records corresponding to SVs of 2 or 

greater (i.e., the emissions exceeded the Tier 1 threshold). Emissions and screening thresholds not shown for space purposes. a

The emission screening threshold for mercury applies to emissions of divalent mercury, although EPA derived it based on 

hazards associated with ingestion of fish contaminated with methyl mercury (i.e., emissions of divalent mercury, which transforms 

to methyl mercury within the environment, accumulates in fish tissue, and is consumed by the fisher). The contribution from 

hazards associated ingestion of divalent mercury from contaminated FFC or fish media is relatively minimal.
Human Health Multipathway Residual Risk Screening Assessment for the Phosphate Fertilizers 

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Draft 18 July 2014 

6. References 

ESRI (Environmental Systems Research Institute). 2014. World Imagery. Accessed June 12, 

2014. Available at: 

http://www.arcgis.com/home/item.html?id=10df2279f9684e4a9f6a7f08febac2a9. 

Seinfeld, J.H., and S.N. Pandis. 1998. Atmospheric Chemistry and Physics: From Air Pollution 

to Climate Change, Wiley-Interscience, New York, pp. 931–933.