Contents 

1. DESCRIPTION OF PETROLEUM COKE .......................................................................... 1

1.1. Composition and Structure............................................................................................. 1

1.2. Coking Processes and Terminology .............................................................................. 2

1.3. Analytical Characterization............................................................................................. 3

2. CATEGORY DEFINITION AND JUSTIFICATION ............................................................. 4

3. TEST MATERIALS............................................................................................................. 4

3.1. Previous Studies ............................................................................................................ 4

3.2. New Studies ................................................................................................................... 4

4. PHYSICAL-CHEMICAL PROPERTIES.............................................................................. 5

4.1. Physical-Chemical Screening Information Data Set (SIDS) .......................................... 5

4.2. Assessment Summary for Physical-Chemical Endpoints .............................................. 6

5. ENVIRONMENTAL FATE .................................................................................................. 6

5.1. Environmental Fate Endpoints ....................................................................................... 6

5.1.1. Photodegradation....................................................................................................... 6

5.1.1.1. Direct ..................................................................................................................... 6

5.1.1.2. Indirect................................................................................................................... 6

5.1.2. Stability in Water........................................................................................................ 6

5.1.3. Transport Between Environment Compartments Fugacity/Distribution..................... 7

5.1.4. Biodegradation........................................................................................................... 7

5.2. Assessment Summary for Environmental Fate.............................................................. 7

6. ENVIRONMENTAL EFFECTS ........................................................................................... 8

6.1. Aquatic Toxicity .............................................................................................................. 8

6.1.1. Aquatic Endpoints...................................................................................................... 8

6.1.2. Acute Toxicity to Aquatic Vertebrates........................................................................ 8

6.1.3. Acute Toxicity to Freshwater Invertebrates ............................................................... 9

6.1.4. Acute Toxicity to Aquatic Plants ................................................................................ 9

6.2. Terrestrial Toxicity........................................................................................................ 10

6.2.1. Terrestrial Endpoints................................................................................................ 10

6.2.2. Toxicity to Terrestrial Plants .................................................................................... 10

6.2.3. Toxicity to Soil Dwelling Organisms......................................................................... 11

6.3. Assessment Summary for Environmental Effects................................................11

7. HUMAN HEALTH ENDPOINTS......................................................................12

7.1. Human Health Effects .................................................................................................. 12

7.1.1. Acute Toxicity........................................................................................................... 12

7.1.2. Repeated-Dose Toxicity........................................................................................... 13

7.1.3. Genetic Toxicity ....................................................................................................... 14

7.1.3.1. In Vitro ................................................................................................................. 14

7.1.3.2. In Vivo.................................................................................................................. 15

7.1.4. Reproductive and Developmental Toxicity .............................................................. 16

7.2. Health Effects Other..................................................................................................... 17

7.2.1. Carcinogenicity ........................................................................................................ 17

7.3. Assessment Summary for Health Effects .................................................................... 17

8. MATRIX OF PETROLEUM COKE CATEGORY DATA ................................................... 18

9. CATEGORY ANALYSIS CONCLUSIONS ....................................................................... 19

10. REFERENCES................................................................................................................. 20

11. LIST OF ABBREVIATIONS AND ACRONYMS ............................................................... 25

12. GLOSSARY...................................................................................................................... 26

APPENDIX A - Category Members ............................................................................................... 31

APPENDIX B - Composition of Green Coke Samples Used in Toxicology Studies ..................32 

Petroleum Coke Robust Summaries located at http://www.epa.gov/hpvis/index.html

ii 
SUMMARY 

The Petroleum Coke category consists of two substances; green coke and calcined coke. These 

two substances are grouped together in a category based on their similarity of manufacturing 

processes which results in similar physical chemical characteristics and chemical composition. 

The principal difference is the amount of residual hydrocarbon (also termed volatile matter) in the 

two products. Petroleum coke (both green and calcined) is a black-colored solid produced by the 

high pressure thermal decomposition of heavy (high boiling) petroleum process streams and 

residues. Green coke is the initial product from the cracking and carbonization of the feedstocks 

to produce a substance with a high carbon-to-hydrogen ratio. Green coke undergoes additional 

thermal processing to produce calcined coke. The additional processing removes volatile matter 

and increases the percentage of elemental carbon, which results in a lower potential for toxicity 

for calcined coke. 

The hazard potential for the petroleum coke category has been characterized by evaluating 

existing data, testing green coke to fill data gaps, then ‘reading across’ the green coke results to 

the other category member, calcined coke. This is justified because, as stated above, green coke 

contains higher levels of volatile matter, and therefore, it is “worse case” by comparison to 

calcined coke. Physical-chemical properties, environmental fate, environmental effects and 

health effects are summarized below, and more fully discussed in the body of the category 

analysis. The primary routes for human exposure are dermal and inhalation. With the exception 

of in vitro studies, the mammalian health data provided in this report are from inhalation and 

dermal studies. 

Physical-Chemical Properties: 

Because petroleum coke (both green coke and calcined coke) is the substance remaining from 

treating heavy petroleum feedstocks with high temperature and pressure, many of the physicalchemical properties are not meaningful at ambient environmental conditions. At ambient 

temperature and pressure, petroleum coke exists as a solid, and because it consists 

predominantly of elemental carbon and a hardened residuum remaining from the feedstocks, the 

High Production Volume (HPV) Chemical Challenge Program physical-chemical endpoints either 

cannot be measured using recommended testing procedures or would not provide meaningful 

information. 

Environmental Fate: 

If released to the environment, both forms of petroleum coke would not be expected to undergo 

many of the HPV environmental fate pathways. Because petroleum coke is predominantly 

elemental carbon and a hardened residuum, it would not be subject to photolytic processes. 

These substances do not contain hydrolysable chemical bonds, nor are they susceptible to 

biodegradation by microorganisms. Depending on the particle size and density of the material, 

terrestrial releases will become incorporated into the soil or transported via wind or surface water 

flow. If released to the aquatic environment, petroleum coke will either incorporate into sediment 

or float on the surface, depending on the particle size and density in relation to water. 

Ecotoxicity: 

Aquatic and terrestrial ecotoxicity tests were performed to assess the hazard of green petroleum 

coke to representative aquatic organisms and terrestrial soil-dwelling invertebrates and vascular 

plants. Testing of selected terrestrial species was included because petroleum coke is 

sometimes used in a manner that can result in exposure to terrestrial organisms. Aquatic 

exposures were prepared as water accommodated fractions (WAFs) and attempts were made to 

analytically quantify specific organic and inorganic constituents of petroleum coke in the WAF 

solutions. None of those constituents of petroleum coke were present in the WAF solutions at 

iii 
their analytical detection limits. Because a solubility level could not be established by analytical 

means, aquatic toxicity test endpoints were presented as nominal WAF loading rates. Loading 

rate refers to the total amount of petroleum coke added per unit volume of water to produce the 

WAF. Similarly, endpoints of terrestrial toxicity tests were reported as nominal concentrations of 

green petroleum coke in soil because constituents of petroleum coke could not be measured in 

soil at the established exposure level. 

Aquatic Hazard: Results of acute aquatic toxicity testing of three species were: 

Fish (fathead minnow, Pimephales promelas): 96-h LL50 > 1000 mg/L 

 96-h NOELR = 1000 mg/L 

 Invertebrate (Daphnia magna): 48-h EL50 > 1000 mg/L 

 48-h NOELR = 1000 mg/L 

 Alga (Selenastrum capricornutum): 96-h EbL50 > 1000 mg/L 

 96-h ErL50 > 1000 mg/L 

 96-h NOELR < 1000 mg/L 

Green petroleum coke has a low potential to cause adverse effects on the aquatic environment. 

Terrestrial Hazard: Results of terrestrial toxicity testing resulted in the following: 

 Earthworm (Eisenia fetida): 14-d LC50 >1000 mg/kg 

 14-d NOEC = 1000 mg/kg 

Terrestrial plant (corn, Zea mays): 21-d LC50 >1000 mg/kg 

 21-d NOEC = 1000 mg/kg 

 Terrestrial plant (radish, Raphanaus sativus): 21-d LC50 >1000 mg/kg 

 21-d NOEC = 1000 mg/kg 

 Terrestrial plant (soybean, Glycine max): 21-d LC50 >1000 mg/kg 

 21-d NOEC = 1000 mg/kg 

Green petroleum coke has a low potential to cause adverse effect on the terrestrial environment.

Human Health Effects: 

Humans can be exposed to petroleum coke primarily via the dermal and inhalation routes. The 

majority of the existing animal toxicity studies have been conducted on green coke which has a 

higher volatile matter content than calcined coke. Due to the physical-chemical characteristics of 

coke described above, and the lack of systemic toxicity observed in a mouse lifetime dermal 

study, inhalation was considered to be the route of exposure with the greatest potential to 

demonstrate hazard. The majority of the mammalian health data provided in this report describe 

inhalation studies. 

Acute Toxicity: There are no single dose acute studies on petroleum coke. Repeated-dose 

inhalation studies on green coke demonstrated a low degree of toxicity with no treatment-related 

deaths. Based on the OECD 421 Reproductive/Developmental Toxicity Screening Test (see 

below), the acute inhalation LC50 for both green and calcined coke is estimated to be > 300 

mg/m3

. Petroleum coke has a low acute toxicity hazard potential. 

Repeated-Dose Toxicity: No Screening Information Data Set (SIDS) guideline repeated-dose 

studies have been conducted on petroleum coke. Two-year carcinogenicity/chronic toxicity 

studies on green coke have been conducted in rats and monkeys. Inhalation of petroleum coke in 

these two studies caused inflammatory and non-oncogenic proliferative changes in the nose and 

lungs in rats, but not monkeys. These portal-of-entry effects were considered to be non-specific 

iv 
responses of the respiratory tract to high concentrations of insoluble particles rather than 

compound specific-induced effects, and are supported by the lack of systemic toxicity observed in 

the two-year animal studies. Using results of two-year chronic toxicity/carcinogenicity studies in 

rats and monkeys, a conservative estimate of the portal-of-entry repeated-dose LOAEL was < 10 

mg/m3

, and the inhalation repeated-dose systemic NOAEL was estimated to be >30 mg/m3. 

Additionally, green coke was not carcinogenic in rats or monkeys at 30 mg/m3

 (the highest 

concentration tested). Petroleum coke repeated-dose hazard potential is low. 

In Vitro Genetic Toxicity – Gene mutation: Green coke was not mutagenic in standard in vitro

genetic toxicity tests in bacteria and mammalian cells. However, when tested in a modification of 

the Salmonella bacterial mutagenicity assay developed for petroleum substance testing, the 

dimethyl sulfoxide (DMSO) extracts of petroleum coke were mutagenic. 

In Vivo Genetic Toxicity: Green coke has been evaluated in three inhalation studies for the ability 

to produce chromosome aberrations in a bone marrow cytogenetics assay. In the first study, no 

aberrations were observed in rats after 20 days of exposure to 10 or 40 mg/m3 petroleum coke. In 

a second study, an increase in chromosomal abnormalities was seen after 5 days of treatment at 

the same exposure concentrations used in the first study. However, it was later determined that 

the slides from the second study had been misread, and that the results from the second study 

should be considered inconclusive. To resolve uncertainty, a third in vivo cytogenetics study was 

conducted on bone marrow from male and female rats in the chronic inhalation study. 

Chromosomal aberrations were not seen in this third study after 5 days, 12 months or 22 months 

of exposure to petroleum coke at 10 or 30 mg/m3

. The weight of the evidence from these three 

studies indicates that green coke was not genotoxic in in vivo bone marrow chromosome 

cytogenetic assays. Petroleum coke has a low potential to cause genetic toxicity based on in vivo

testing. 

Reproductive and Developmental Toxicity: No reproductive or developmental effects were 

observed in an OECD 421 Reproductive/Developmental Toxicity Screening Test at green coke 

concentrations up to 300 mg/m3

 (the highest concentration tested). The parental systemic toxicity, 

reproductive toxicity, and developmental toxicity NOAELs were all > 300 mg/m3

. The reproductive 

and developmental toxicity hazard potential for petroleum coke is low. 

Carcinogenicity: Petroleum coke was not carcinogenic in three carcinogenicity studies. Rats and 

monkeys were exposed via inhalation five days/week for two years to 0, 10, or 30 mg/m3

 green 

coke. No excess cancers were observed. In a lifetime skin painting study, mice were exposed to 

0 or 100 μl of 250 mg/mL green coke and no excess skin or visceral cancers were observed. 

Conclusions: Based on the data summarized above and discussed in greater detail in the body 

of this document, both green coke and calcined coke (using read-across from green coke) have a 

low potential for inducing adverse effects to the environment and, with the exception of noncompound-specific, insoluble particle portal-of-entry effects, to human health. 

v 
1. DESCRIPTION OF PETROLEUM COKE 

Petroleum coke is produced through the thermal decomposition of heavy petroleum 

process streams and residues. The three most common feedstocks used in coking 

operations are 1) reduced crude (vacuum residue), 2) thermal tar, and 3) decant oil 

(catalytically cracked clarified oil) (Onder and Bagdoyan, 1993). These feedstocks are 

heated to thermal cracking temperatures and pressures (485 to 505°C at 400 kPa) that 

create petroleum liquid and gas product streams. The material remaining from this 

process is a solid concentrated carbon material, petroleum coke (Ellis and Paul, 2000b; 

EC, 2003). 

Petroleum cokes can be categorized as either green or calcined coke. The initial product 

of the coking process, green coke, is used as fuel, in gasification and metallurgical 

processes, or as feedstock to produce calcined coke. Calcined coke is produced when 

green coke is treated to higher temperatures (1200 to 1350°C). The primary use of 

calcined coke is in making carbon anodes for the aluminum industry. Other uses include 

making graphite electrodes for arc furnaces, titanium dioxide, polycarbonate plastics, 

steel, carbon refractory bricks for blast furnaces, packing media for anode baking 

furnaces, and material for cathodic protection of pipelines (Ellis and Paul, 2000a; EC, 

2003). 

1.1. Composition and Structure 

Petroleum coke is composed primarily of elemental carbon organized as a porous 

polycrystalline carbon matrix. In green coke, the pores of the matrix are filled with a 

hardened residuum remaining from the coker feed (Al-Haj-Ibrahim and Morsi, 1992; AlHaj-Ibrahim and Ali, 2005). This residuum is referred to as volatile matter1

 (sometimes 

referred to as residual hydrocarbon) because it distills off during the calcining process 

(Al-Haj-Ibrahim and Ali, 2005; ASTM International, 2004a). Volatile matter consists of the 

heavy hydrocarbons remaining from the feedstocks that have not undergone complete 

carbonization (EC, 2003). Green coke normally contains between 4% and 15% volatile 

matter, but can contain up to 21% (CONCAWE, 1993; Al-Haj-Ibrahim and Morsi, 1992; 

IUPAC, 1995). The temperature of the coking drum as well as cycle time and drum 

pressure all affect the amount of volatile matter in green and calcined coke (Ellis and 

Paul, 2000b). Because of the lower temperature used in its production, green coke 

contains higher levels of volatile matter than calcined coke. 

The specific chemical composition of any given batch of petroleum coke is determined by 

the composition of the feedstocks used in the coking process, which in turn are 

dependent upon the composition of the crude oil and refinery processing from which the 

feedstock is derived (Al-Haj-Ibrahim and Morsi, 1992; CONCAWE, 1993; Dalbey et al., 

1998; Ellis and Paul, 2000b). Cokes produced from feedstocks high in asphaltenes will 

contain higher concentrations of sulfur and metals than cokes produced from high 

aromatic feedstocks (Onder and Bagdoyan, 1993). This is because asphaltenes contain 

a disproportionate fraction of those heteroatoms (Onder and Bagdoyan, 1993; Siskin et 

al., 2006). Most of the sulfur in coke exists as organic sulfur bound to the carbon matrix. 

However, the structure of organic sulfur compounds in petroleum coke is largely 

unknown, and no precise analytical methods are available to determine these structures 

(Al-Haj-Ibrahim and Morsi, 1992). Other forms of sulfur found in coke include sulfates 

and pyritic sulfur, but these rarely make up more than 0.02% of the total sulfur in coke 

(Al-Haj-Ibrahim and Morsi, 1992). Metals, mainly vanadium and nickel, occur as metal 

chelates or porphyrins in the asphaltene fraction (Ellis and Paul, 2000a,b). Some metals 

are intercalated in the coke structure and are not chemically bonded, so they become 

 

1

Volatile matter is hydrocarbons that are driven out of petroleum coke at 950oC (1742oF) under strictly controlled 

conditions per ASTM method D 6374-99 

1 
part of the ash and particulates (Ellis and Paul, 2000b). Metal concentrations in coke 

normally increase upon calcining due to the weight loss from evolution of the volatile 

matter (Lee et al., 1997; Ellis and Paul, 2000a). In practice, however, calcined cokes 

typically contain lower metal concentrations than many grades of green coke due to the 

selection of low-metal green cokes for calcining (Lee et al., 1997).

1.2. Coking Processes and Terminology 

Petroleum coke is formed from two basic reactions, dealkylation and dehydrogenation 

(Onder and Bagdoyan, 1993). 

Dealkylation – When high molecular weight compounds such as asphaltenes and 

resins are subject to elevated temperatures in the coker unit, the resulting carbon 

residue is a highly disordered and cross-linked structure. This is marked by a 

significant difference in the concentration of hydrogen atoms measured in the resinasphaltene feed and the formed coke. The carbon to hydrogen ratio increases from 

a range of 8-10 in the feed to 20-24 in the coke. This amorphous character, 

combined with high concentrations of impurities, render the coke produced from 

resin-asphaltene compounds unsuitable for special applications. 

Dehydrogenation – This mechanism depends on the dehydrogenation of heavy oils 

with subsequent condensation of free radicals to form high molecular weight 

compounds with high carbon-to-hydrogen ratios. The coke thus produced contains 

fewer cross-linkages and has a more crystalline appearance than the resinasphaltene based coke. Coke formed from feedstocks such as thermal cracker tars, 

catalytic cracker slurry, and decant oil, which are high in aromatics and low in resinasphaltenes, is a premium grade product suitable for calcining and graphitization. 

Green coke can be produced by one of three processes: delayed, fluid or flexicoking. 

Delayed process coke is produced by a semi-continuous batch process and accounts for 

more than 92% of total coke production in the United States (Pace Consultants Inc., 

2001). Fluid coke is produced by a continuous fluidized bed process. Fluid coke typically 

contains less volatile matter than delayed process green coke but more than calcined 

coke, and occurs as spherical grains less than 1 cm in diameter (CONCAWE, 1993). 

Flexicoke is produced by a variant of the fluidized bed process in which most of the coke 

(up to 97%) is converted to a low heating value (20 to 40 Btu/scf) fuel gas for use at the 

refinery where it was produced. Solid flexicoke has a smaller particle size than fluid coke 

and is dustier due to its lower volatile matter content (CONCAWE, 1993; Roundtree, 

1998). 

Depending on its physical form, green coke produced in delayed cokers may also be 

classified as shot, sponge or needle coke. Shot coke occurs as small, hard spheres and 

is derived from low API gravity and high asphaltene and resin petroleum precursors via 

the dealkylation reaction mechanism. Sponge coke is the most common form of green 

coke and it has a macroscopically amorphous appearance. Visibly, it has a dull black 

color and a porous consistency with walls and pores that vary in size. It is normally 

derived from virgin petroleum feedstocks, which contain large numbers of cross linkages. 

Gas bubble percolation inside the coke drum may also account for generation of some 

sponge coke. In reality, sponge coke is a mixture of shot and needle coke structures. 

Needle coke appears as silver-gray colored ocicular structures (ribbon-like, crystalline 

needles) and is derived from feedstocks with high aromatic hydrocarbon content via the 

dehydrogenation reaction mechanism (Lee et al., 1997; Ellis & Paul, 2000b). 

Calcined coke is produced from green coke by a process of further heating at 

temperatures in excess of 1200o

C (CONCAWE, 1993). Most uses other than for fuel or 

gasification require green coke to be calcined in order to improve its properties. The 

2 
process of calcining removes moisture, reduces the volatile matter to less than 0.4%, 

increases the density of the coke structure, increases physical strength, and increases 

the electrical conductivity of the material (Ellis and Paul, 2000a). When green coke is 

calcined, devolatilization of volatile matter occurs at 500 to 1000°C. Heating further to 

1200 to 1400°C causes additional dehydrogenation, some desulfurization, and coke 

structural shrinkage (densification) (Ellis and Paul, 2000a). The result is a hard, dense 

substance with low hydrogen content, a low coefficient of thermal expansion, and good 

electrical conductivity. These properties along with low metals and ash contents make 

calcined petroleum coke highly desirable for use in the aluminum smelting industry (Ellis 

and Paul, 2000a). Calcined coke is characterized as either anode-grade coke or graphite 

needle-grade coke depending upon its physical and chemical characteristics, with 

needle-grade coke having a higher purity (i.e., lower ash, sulfur, and metals contents 

(Lee et al., 1997) than anode-grade coke, which is used in electric furnaces in aluminum 

and steel smelting. The physical characteristics of petroleum coke are important in 

determining the suitability of a coke sample for a specific use. These characteristics are 

typically the real and bulk densities and, in the case of anode and needle grade coke, the 

resistivity and coefficient of thermal expansion. Fuel grade coke may also be 

characterized by its fuel value (Btu/lb). 

Green coke and calcined coke are covered by two separate definitions of petroleum coke 

in the Chemical Abstract Service and EINECS Registry systems. They are: Petroleum 

coke and Coke (petroleum) calcined. The definitions of these substances are listed in 

Appendix 1. 

1.3. Analytical Characterization 

Physical and compositional characteristics considered important in petroleum coke 

include weight % ash, weight % sulfur, weight % volatile matter, nickel (mg/kg), and 

vanadium (mg/kg) (Lee et al., 1997). Examples of selected physical and compositional 

characteristics between fuel grade green and aluminum grade calcined coke are shown 

in Table 1. 

Table 11 

Comparison of Green and Calcined Coke Composition

Properties2 Fuel-Grade Green 

Coke 

Anode-grade calcined 

Coke 

Sulfur (wt%) 2.5 – 5.5 1.7 – 3.0 

Ash (wt%) 0.1 – 0.3 0.1 – 0.3 

Nickel (ppm) N.D.3 165 – 350 

Vanadium (ppm) 200 – 400 120 – 350 

Volatile matter (wt%) 9 – 12 <0.25 

Bulk density (g/cm3) N.D. 0.80 

Real density (g/cm3) N.D. 2.06 

1

From Lee et al., 1997 

2

The above values are given for illustration and may vary depending upon the 

feedstock or crude oil of origin 

3

Not determined 

Analyses of green petroleum coke have measured various polyaromatic compounds 

(PACs) and metals in neat samples. Organic solvent extracts of green petroleum coke 

prepared for gas chromatographic analyses have revealed various parent and alkylated 

polyaromatic hydrocarbons (CONCAWE, 1993; Dalbey, et al., 1998). Metals also have 

been measured in neat green coke samples by X-ray fluorescence or inductively coupled 

plasma spectroscopic methods (Ellis and Paul, 200a). Characterization data of green 

coke test samples used in HPV testing confirmed low concentrations of both PACs and 

metals in such preparations (Appendix B). In contrast, metals and selected PACs were 

3 
not found in detectable concentrations in aqueous WAF solutions used in aquatic toxicity 

tests conducted for the HPV testing program (Wildlife International Ltd., 2006a-c). 

2. CATEGORY DEFINITION AND JUSTIFICATION 

The petroleum coke category contains two substances (see Appendix 1 for full CAS 

definitions): 

Coke (petroleum) [also known as green coke] CAS # 64741-79-3 

Coke (petroleum), calcined CAS # 64743-05-1 

These substances are grouped together in one category based on a similarity of their 

manufacturing processes, which results in similar physical chemical characteristics and 

chemical composition. Green coke undergoes additional thermal processing to produce 

calcined coke. The additional processing removes volatile matter and increases the 

percentage of elemental carbon, which results in calcined coke having a lower potential 

for toxicity. Therefore, the hazard potential for the petroleum coke category was 

characterized by testing green coke, then ‘reading across’ from the green coke results to 

calcined coke. 

3. TEST MATERIALS 

3.1. PREVIOUS STUDIES 

Analytical data for green coke samples used in previous and new toxicity studies are 

presented in Appendix B. 

3.2. NEW STUDIES 

To select a sample of green coke for studies to fill data gaps2

 with the highest potential 

for health and environmental effects, delayed green coke analytical data from a 

database on U.S. coke dating since 1983 were evaluated (Pace Consultants, Inc., 

2001). Samples of green coke produced from the delayed coking process were selected 

over cokes derived using the fluid or flexicoking processes because delayed green coke 

constitutes 92% or more of the U.S. coking production (Pace Consultants, Inc., 2001), 

and delayed green coke typically contains higher percentages of volatile matter 

(CONCAWE, 1993). Specifically, data from 1998 and 1999 were evaluated for sulfur (wt 

%), nickel (ppm), vanadium (ppm), and volatile matter (wt %). The 1999 dataset 

contained data on over 92% of the coke produced in the U.S. that year. No single 

candidate refinery produced green coke with the highest content in all four properties, so 

some compromise was required for test material producer selection. Table 2 

summarizes the ranges of sulfur, nickel, vanadium and hydrocarbon content for coke 

produced by the five candidate refineries and lists the coke quality data properties from 

the candidate refinery selected to provide test material for studies to fill the HPV 

endpoint data gaps (Pace Consultants Inc., 2001). 

Table 21 

 

2

 OECD 203 Fish acute toxicity test; OECD 202 Invertebrate acute toxicity test; OECD 201 Algal growth inhibition test; 

OECD 208 Seedling emergence and growth of terrestrial plants; OECD 207 Earthworm acute toxicity test; OECD 421 

Reproduction/developmental toxicity test 

4 
Comparison of Properties of Green Coke from Supplier Candidates and Selected 

Green Coke Supplier for HPV Test Material

Five Candidate Refinery Coke 

Quality Ranges 

Coke Quality for 

Refinery that 

Provided HPV 

Testing Sample 

Property 

Value Percentile Value Percentile

Sulfur (Wt. %) 4.20 – 6.00 43 - 93 5.75 86 

Nickel (ppm) 250 - 500 50 - 90 300 58 

Vanadium (ppm) 1,000 – 1,500 65 - 84 1,200 75 

Volatile Matter (Wt. 

%) 

10.0 – 15.0 25 - 100 12.0 75 

1

 Pace Consultants Inc., 2001 

Detailed analysis of the selected green coke test sample is provided in Appendix B. 

4. PHYSICAL-CHEMICAL PROPERTIES 

Petroleum coke is a product of extreme temperature and pressure treatments that 

convert heavy petroleum feedstocks into a solid substance composed predominately of 

carbon. Because of its structural and compositional characteristics, developing the 

physical-chemical and environmental fate endpoints of the HPV program would not be 

feasible using standard OECD testing methods. 

4.1. Physical-Chemical Screening Information Data Set (SIDS) 

The physical-chemical endpoints in the HPV chemicals program include the following: 

 Melting Point 

 Boiling Point 

 Vapor Pressure 

 Octanol/Water Partition Coefficient 

 Water Solubility 

Green petroleum coke exists as a solid substance composed of predominately carbon in 

a polycrystalline porous matrix. Approximately nine to 21% by weight of green petroleum 

coke is volatile matter that it is driven off during calcinations. This substance exists in 

green coke as a hardened residuum in the carbon matrix (Al-Haj-Ibrahim and Morsi, 

1992; Al-Haj-Ibrahim and Ali, 2005). Due to the extreme temperature and pressure under 

which petroleum coke is produced, melting point, boiling point, and vapor pressure 

measurements would not reveal meaningful data at ambient environmental conditions. 

For similar reasons, measurements of partition coefficient and water solubility are not 

possible for green petroleum coke. Partition coefficient and water solubility require 

analytical measurements of the test substance in n-octanol and/or water. While selected 

organic solvents have demonstrated an ability to extract some of the organic fraction from 

the neat green coke (Dalbey et al., 1998; Clayton Environmental Consultants, 1983; 

Monarca et al., 1982; Klonne et al., 1987), attempts to measure selected hydrocarbon 

compounds and inorganic components of petroleum coke in water extracts failed at the 

detection limits of the analytical methods (e.g. 5 μg/L for the organic fraction, 0.4 μg/L to 

200 μg/L for metals, and 5.1 mg/L for sulfur (Wildlife International, Ltd., 2007a-c). 

Because components in green petroleum coke were insufficiently soluble in water, 

neither water solubility nor partition coefficient measurements can be made. 

5 
Conclusions: The HPV physical-chemical endpoints for green or calcined petroleum 

coke either cannot be measured or would not provide meaningful data at ambient 

environmental conditions. 

4.2. Assessment Summary for Physical-Chemical Endpoints 

Green petroleum coke is a complex mixture of mostly elemental carbon with inorganic 

and organic constituents embedded in a solid poly-crystalline porous matrix. Under 

ambient environmental conditions, characteristics of melting point, boiling point, vapor 

pressure, partition coefficient, and water solubility cannot be measured in either green or 

calcined petroleum coke due to analytical limitations or the physical nature of petroleum 

coke.

5. ENVIRONMENTAL FATE 

5.1. Environmental Fate Endpoints 

5.1.1. Photodegradation 

5.1.1.1. Direct 

A prerequisite for direct photodegradation is the ability of one or more bonds within a 

chemical to absorb ultraviolet (UV)/visible light in the 290 nm to 750 nm wavelength 

range. Light wavelengths longer than 750 nm do not contain sufficient energy to break 

chemical bonds, while wavelengths below 290 nm are shielded from the earth by the 

stratospheric ozone layer (Harris, 1982a). Because petroleum coke consists of mostly 

elemental carbon, there are no chemical bonds upon which direct or indirect 

photochemical reactions may act. Photodegradation of residual constituents in petroleum 

coke (e.g., metals and high molecular weight hydrocarbons) would not be expected to 

take place. These substances are neither water-soluble nor volatile at ambient 

temperatures, thus would not engage in direct or indirect photochemical reactions. 

Therefore, direct photodegradation is not an important fate process for petroleum coke. 

5.1.1.2. Indirect 

Indirect photodegradation occurs in the atmosphere when organic chemicals react with 

photosensitized oxygen in the form of hydroxyl radicals. Atmospheric oxidation as a 

result of hydroxyl radical attack is not direct photochemical degradation but an indirect 

degradation process. Because petroleum coke consists mostly of elemental carbon and 

other residual constituents that are generally non-volatile at ambient temperatures, 

indirect photodegradation is not an important fate process for petroleum coke. 

Conclusion: Direct and indirect photodegradation are not important fate processes for 

green or calcined petroleum coke. 

5.1.2. Stability in Water 

Hydrolysis of an organic molecule occurs when a molecule (R-X) reacts with water (H2O) 

to form a new carbon-oxygen bond after the carbon-X bond is cleaved (Harris, 1982b). 

This reaction is referred to as nucleophilic substitution, where X is the leaving group 

being replaced by the incoming nucleophilic oxygen from the water molecule. The 

leaving group, X, must be a molecule other than carbon because carbon atoms lacks 

sufficient electronegativity to serve as a good leaving group (i.e., carbon-carbon bonds 

are too stable to be cleaved by nucleophilic substitution). Chemicals that have a potential 

6 
to hydrolyze include alkyl halides, amides, carbamates, carboxylic acid esters and 

lactones, epoxides, phosphate esters, and sulfonic acid esters (Harris, 1982b). 

Petroleum coke is composed of elemental carbon and other components that are not 

susceptible to nucleophilic substitution. Therefore, petroleum coke is not subject to 

hydrolysis, and this fate process will not be an important degradative pathway in the 

environment. 

Conclusion: Hydrolysis is not an important degradative pathway for green or calcined 

petroleum coke. 

5.1.3. Transport Between Environment Compartments Fugacity/Distribution 

Elemental carbon and the residual components are neither sufficiently water soluble nor 

volatile in the environment to be evaluated by fugacity-based multimedia modeling. If 

released to the environment, petroleum coke is expected to be chemically and physically 

inert. Depending on the particle size and density of the material, terrestrial releases will 

become incorporated into the soil or transported via wind or surface water flow. If 

released to the aquatic environment, petroleum coke will either be incorporated into 

sediment or float on the surface, depending on the particle size and density in relation to 

water. 

Conclusion: Green and calcined petroleum coke are expected to be chemically and 

physically inert in the environment, with transport related to particle size and density in 

relation to wind and water. 

5.1.4. Biodegradation 

Biodegradation occurs when microorganisms transform an organic molecule into carbon 

dioxide, water, and energy. The reduction or oxidation of chemical bonds in an organic 

molecule provides the energy and carbon to build new cell material. Petroleum coke is 

composed mainly of elemental carbon which does not contain the chemical bonds that 

microbes require for metabolism. Other constituents embedded in the carbon matrix 

include inorganic substances and high molecular weight hydrocarbon compounds 

remaining as residuum from the coking process. These constituents would not be 

expected to be available for microbial degradation. Therefore, biodegradation is not 

considered an important fate process for petroleum coke. 

Conclusion: Biodegradation is not considered an important fate process for green or 

calcined petroleum coke. 

5.2. Assessment Summary for Environmental Fate 

Green and calcined petroleum coke are complex mixtures of mostly elemental carbon 

with inorganic and organic constituents embedded in the carbon matrix. In general, these 

constituents do not contain the chemical bonds that engage in photolytic or hydrolytic 

reactions. If released to the environment, petroleum coke would be expected to be nonreactive and either disperse or remain in the environmental compartment to which it was 

released. 

Therefore, depending on factors such as particle size and density relationships of the 

petroleum coke and environmental media, releases to terrestrial or aquatic environments 

would result in incorporation of the material into soils/sediments or dispersal via 

wind/water action. Biodegradation would not be an important fate process because the 

7 
majority of the constituents in petroleum coke do not contain the chemical bonds needed 

for microbial metabolism. 

6. ENVIRONMENTAL EFFECTS 

6.1. AQUATIC TOXICITY 

6.1.1. Aquatic Endpoints 

The potential hazard of green petroleum coke to freshwater aquatic organisms was 

assessed by testing a fish (Pimephales promelas), an invertebrate (Daphnia magna), and 

an alga (Selenastrum capricornutum). All studies employed aqueous exposure solutions 

prepared as water accommodated fractions (WAFs) in accordance with OECD 

recommendations for testing complex mixtures having low water solubility (OECD, 

2000a). Green coke used to prepare the WAF solutions was milled and sieved to 

approximately 2 mm grain size and was separated from the aqueous phase following a 

period of mixing. Under an aquatic spill scenario, adverse effects of petroleum coke on 

aquatic organisms potentially could arise due to physical effects of coke particulate 

matter on respiratory membranes of the organisms. The 2 mm grain size allowed the 

segregation of the solid particles following the preparation of the WAF solutions. 

Prior to testing, the test sample of green petroleum coke was characterized for a series of 

specific inorganic constituents and predominantly un-alkylated polycyclic aromatic 

hydrocarbons (PAH). A subset of those analytes and compounds were used as markers 

in the WAF solutions during each aquatic toxicity test. Attempts to measure these 

constituents in fresh and aged WAF solutions used in the three aquatic toxicity tests 

showed their concentrations to be less than the minimum quantifiable limits for the 

methods used (detection limits were 5μg/L for PAHs, 0.4 μg/L to 200 μg/L for metals, and 

5.1 mg/L for sulfur). The aquatic toxicity test endpoints are presented as nominal WAF 

loading rates. Acute effects on aquatic organisms are unlikely except at concentrations 

above the solubility limits of the measured constituents. However, the solubility limits 

could not be defined in these tests because of the extremely low solubility of those 

constituents from the coke matrix and the limits of the analytical methodology. 

6.1.2. Acute Toxicity to Aquatic Vertebrates 

The test with the fathead minnow (P. promelas) was conducted following OECD (OECD, 

1992) and EPA guidelines (US EPA, 1996a) as a 96-hour static-renewal limit test using a 

negative control group and a single petroleum coke (green coke) WAF prepared at a 

loading rate of 1000 mg/L. Each experimental group consisted of 30 fish divided among 

three test chambers (10 fish/replicate). Test chambers were completely filled with no 

headspace and sealed to mitigate potential loss of any component during the testing 

period. Fresh WAF solutions were prepared daily and fish were transferred to the fresh 

solutions after approximately 24, 48 and 72 hours of the 96-hour exposure period 

(Wildlife International Ltd., 2006a). 

No mortality occurred, and no clinical signs of toxicity were evident among the fish of the 

control and 1000 mg/L WAF exposure groups during the 96-hour exposure period. The 

endpoints of the test were defined as follows: 

96-hour LL50 > 1000 mg/L (WAF nominal loading rate) 

96-hour no mortality level = 1000 mg/L (WAF nominal loading rate) 

96-hour NOELR = 1000 mg/L (WAF nominal loading rate) 

8 
Conclusion: The results of this study indicate that WAFs of green petroleum coke are 

not acutely toxic to freshwater fish at the loading rate used in the test.

6.1.3. Acute Toxicity to Freshwater Invertebrates 

The test with the freshwater invertebrate, Daphnia magna, was conducted following 

OECD (OECD, 1984a) and EPA (US EPA, 1996b) guidelines as a 48-hour static-renewal 

limit test using a negative control group and a single petroleum coke (green coke) WAF 

prepared at a loading rate of 1000 mg/L. Each experimental group consisted of 30 D. 

magna divided among three test chambers (10 animals/replicate). Test chambers were 

completely filled with no headspace and sealed to mitigate loss of any component during 

the testing period. Fresh WAF solutions were prepared after approximately 24 hours, 

and animals were transferred to the fresh solutions (Wildlife International Ltd., 2006b). 

No immobility occurred, and no clinical signs of toxicity were evident among the 

invertebrates of the control and 1000 mg/L WAF exposure groups during the 48-hour 

exposure period. The endpoints of the test were defined as follows: 

48-hour EL50 >1000 mg/L (WAF nominal loading rate) 

48-hour no immobility level = 1000 mg/L (WAF nominal loading rate) 

48-hour NOELR = 1000 mg/L (WAF nominal loading rate) 

Conclusion: The results indicate that WAFs of green petroleum coke are not toxic to 

freshwater aquatic invertebrates at the loading rate used in the test. 

6.1.4. Acute Toxicity to Aquatic Plants 

The test with the freshwater alga, Selenastrum capricornutum, was conducted following 

OECD (OECD, 1984b) and EPA (US EPA, 1996c) guidelines as a 96-hour limit test using 

a negative control group and a single petroleum coke (green coke) WAF prepared at a 

loading rate of 1000 mg/L. The WAFs were prepared in freshwater algal nutrient medium 

and added to sterile 300-mL BOD bottles. Each bottle was inoculated with algal cells to 

achieve an initial cell density of 5,000 cells/mL. BOD bottles were completely filled and 

sealed to mitigate loss of any component during the test period. Bottles were incubated 

under constant illumination, and cell densities were determined using a hemocytometer 

and microscope from samples taken at 24, 48, 72, and 96 hours. Cell count data were 

used to calculate the area under the growth curve (AUGC) and average specific growth 

rate (μ) (Wildlife International Ltd., 2006c). 

Some slight inhibition of growth (AUGC) and growth rate (μ ) were found in the 1000 

mg/L WAF when compared to the control group at 72 hours (26% and 12%, respectively) 

and at 96 hours (28% and 7.1%, respectively). Differences were noted as statistically 

significant (p = <0.05), although no such effect was observed in prior range finding testing 

of algae. The endpoints of the test were defined as follows: 

72-hour EbL50 >1000 mg/L (WAF nominal loading rate) 

72-hour ErL50 >1000 mg/L (WAF nominal loading rate) 

72-hour NOELR <1000 mg/L (WAF nominal loading rate) 

96-hour EbL50 >1000 mg/L (WAF nominal loading rate) 

9 
96-hour ErL50 >1000 mg/L (WAF nominal loading rate) 

96-hour NOELR <1000 mg/L (WAF nominal loading rate) 

Conclusion: The results indicate that WAFs of green petroleum coke may produce a 

slight growth inhibition in freshwater algae at the loading rate used in the test. 

6.2. TERRESTRIAL TOXICITY 

6.2.1. Terrestrial Endpoints 

Petroleum coke is sometimes used in a manner that can result in exposure to selected 

terrestrial species. For example, it is used in soil as a grounding agent to protect 

sensitive installations from lightning strikes (NLSI, 2002), and it has been experimentally 

used as an absorbent for the removal of crude oil from soils (Narayannan and Arnold, 

1997). Therefore the potential hazards to terrestrial organisms were evaluated. 

The hazards of green petroleum coke to terrestrial organisms were assessed by testing 

an earthworm (Eisenia fetida), and three species of terrestrial plants (corn, Zea mays; 

radish, Raphanaus sativus; and soybean, Glycine max). Testing methods followed 

OECD and/or EPA guidelines. All studies were conducted as limit tests using single 

maximum test concentrations of 1000 mg/kg (dry weight) of green petroleum coke 

incorporated into the soil. Petroleum coke used in terrestrial testing was milled to mean 

particle size of 3.3 μm. The small particle size permitted the incorporation of the 

substance in soil and maximized the potential for contact between the coke particles and 

the test species. 

Prior to testing, the test sample of green petroleum coke was characterized for selected 

inorganic constituents and predominantly un-alkylated polycyclic aromatic hydrocarbons 

(PAH). It was anticipated that those analytes and compounds could be used as dose 

verification markers when analyzed in the soil during each test. Subsequent analytical 

method verification trials showed that the PAH markers were below analytical detection 

limits, while the inorganic metals were not greater than soil background levels. 

Therefore, all terrestrial effects tests were based on the nominal concentration of 

petroleum coke in soil. 

6.2.2. Toxicity to Terrestrial Plants 

Toxicity of green petroleum coke to terrestrial plants was evaluated in a 21-day limit test 

using petroleum coke at a concentration of 1000 mg/kg (dry weight) in soil. Un-treated 

soil was used in the negative control group. Test methodology followed OECD (OECD 

2000b) and EPA (US EPA 1996 d, e) guidelines. Corn (Zea mays), radish (Raphanaus 

sativus), and soybean (Glycine max) were exposed to the soil-incorporated petroleum 

coke and assessed for seedling emergence, survival, growth (measured as both seedling 

height and above-ground dry weight), and seedling condition. The control and exposure 

groups for each test species consisted of four replicate containers holding 1.87 kg (dry 

weight) of soil and 10 seeds (Wildlife International Ltd., 2006d). 

Corn: No statistically significant differences (p > 0.05) were found for seedling 

emergence, seedling survival, seedling height, or shoot dry weight between the dosed 

and control groups. Condition scores revealed no treatment-related effects. The results 

for the test with corn were: 

21-day LC50 > 1000 mg/kg (nominal concentration) 

10 
21-day NOEC = 1000 mg/kg (nominal concentration) 

Radish: No statistically significant differences (p > 0.05) were found for seedling 

emergence, seedling survival, seedling height, or shoot dry weight between the dosed 

and control groups. Condition scores revealed no treatment-related effects. The results 

for the test with radish were: 

21-day LC50 >1000 mg/kg (nominal concentration) 

21-day NOEC = 1000 mg/kg (nominal concentration) 

Soybean: No statistically significant differences (p > 0.05) were found for seedling 

emergence, seedling survival, seedling height, or shoot dry weight between the dosed 

and control groups. Condition scores revealed no treatment-related effects. The results 

for the test with soybean were: 

21-day LC50 >1000 mg/kg (nominal concentration) 

21-day NOEC = 1000 mg/kg (nominal concentration) 

Conclusion: The results indicate that green petroleum coke is not toxic to terrestrial 

plants at the concentration tested.

6.2.3. Toxicity to Soil Dwelling Organisms 

Toxicity of green petroleum coke to earthworms (E. fetida) was evaluated following 

OECD guidelines (OECD, 1984c) in a 14-day limit test using soil-incorporated petroleum 

coke at a concentration of 1000 mg/kg (dry weight). Un-treated soil was used in the 

negative control group. The test and control experimental groups consisted of four 

replicate containers each holding 750 g of soil and 10 earthworms. During the 14-day 

test, the earthworms were assessed for survival, burrowing behavior, general 

appearance, and mean body weight (Wildlife International Ltd., 2006e). 

No mortality occurred in any replicate of the control or the 1000 mg/kg treatment groups, 

and in general, earthworms were normal in appearance. None of the earthworms of the 

control or treatment groups showed any aversion to the soil or in soil burrowing behavior. 

There were no statistical differences (p > 0.05) in earthworm body weight or change in 

body weight when measured at the end of the test. The results of the test were defined 

as follows: 

14-day LC50 >1000 mg/kg (nominal concentration) 

14-day no mortality concentration = 1000 mg/kg (nominal concentration) 

14-day NOEC = 1000 mg/kg (nominal concentration) 

Conclusion: The results indicate that green petroleum coke is not toxic to earthworms at 

the concentration tested.

6.3. Assessment Summary for Environmental Effects 

Petroleum coke (green coke) had no effects on aquatic vertebrates and invertebrates and 

only a slight effect on algae at a WAF loading rate of 1000 mg/L. Petroleum coke did not 

produce any adverse effects in earthworms and three species of terrestrial vascular 

plants at 1000 mg/kg soil. Green coke is considered to have a higher potential to induce 

11 
environmental effects than calcined coke due to green coke’s higher concentration of 

volatile matter. In lieu of testing calcined coke, green coke testing results have been 

conservatively extrapolated to calcined coke (see Table 3). Overall, petroleum coke has 

an extremely low environmental hazard potential.

7. HUMAN HEALTH ENDPOINTS 

Humans are primarily exposed to petroleum coke via the dermal and inhalation routes 

(CONCAWE, 1993). Due to the physical-chemical characteristics of coke described 

above (Section 1), and the lack of systemic toxicity observed in a mouse lifetime dermal 

study (Wingate and Hepler, 1982), inhalation was considered to be the route of exposure 

with the highest hazard potential. Consequently, the inhalation route of exposure was 

used in the one new study (OECD 421 Reproductive/Developmental Toxicity Screening 

Test) performed to fill HPV program data gaps for reproductive and developmental 

endpoints. Similarly, the majority of mammalian health data provided in this report are 

from inhalation studies. 

The majority of the existing animal toxicity studies have been conducted on green coke 

which has a higher volatile matter content than calcined coke. There has been one 

repeated-dose study of limited scope in which calcined coke was tested for comparison 

to the green coke. Summary evaluations of the existing studies and the one newly 

completed study are presented below. Results are summarized in Table 3. 

7.1. Human Health Effects 

7.1.1. Acute Toxicity 

There are no single-dose toxicity studies available on either green or calcined coke. 

In the OECD 421 Reproductive/Developmental Toxicity Screening Test described in 

Section 7.1.2 below, male and female Sprague-Dawley rats were exposed for 6 h/day, 7 

days/week to up to 300 mg/m3

 green coke in the two-week range-finding study and up to 

300 mg/m3

 for a minimum of 35 days in the definitive study. No animals died prior to the 

scheduled termination of the studies. Consequently, the acute inhalation LC50 for green 

coke in rats is estimated to be > 300 mg/m3

 (HLS, 2006). 

A repeated-dose inhalation study was conducted to compare lung responses to green 

and calcined coke (HLS, 1999). In this study, rats were exposed by nose-only inhalation 

for five days to 50 mg/m3 calcined coke or green coke. A silicon dioxide exposure group 

was also used as a benchmark to judge the potential for the coke samples to cause lung 

fibrosis. The average mass median aerodynamic particle sizes were 2.71 μm, 2.69 μm, 

and 1.74 μm for green coke, calcined coke and silicone dioxide, respectively. Lung 

response was evaluated by analysis of lung fluids at 7, 28 and 63 days after exposure. 

No animals died prior to the scheduled sacrifice date. Both green and calcined coke 

caused slight inflammatory responses in the lung, with the response to green coke being 

slightly higher. There was no indication of a fibrogenic response from exposure to either 

the green or calcined coke. The results from this study are consistent with results from 

the rat and monkey inhalation studies and the OECD 421 Reproductive/ Developmental 

Toxicity Screening Test described in more detail in section 7.1.2 below. Importantly, this 

study demonstrated that effects observed with calcined coke were less severe than those 

of green coke, thus supporting category read-across from green coke to calcined coke in 

this category analysis document. 

Conclusions: There are no single dose studies on green or calcined petroleum coke. 

Repeated-dose and OECD 421 inhalation studies demonstrated a low degree of toxicity 

12 
with no treatment-related deaths. Based on the OECD 421 study, the acute inhalation 

toxicity of both green and calcined coke is estimated to be > 300 mg/m3

. 

7.1.2. Repeated-Dose Toxicity 

Two-year whole-body inhalation toxicity studies of sponge-form delayed process green 

coke were conducted in both Sprague-Dawley rats and Cynomolgus monkeys (IRDC, 

1985; Klonne et al., 1987). Both studies were conducted at concentrations of 10 and 30 

mg/m3

 of green coke, which had been micronized into fine particles to aid in aerosol 

generation. The average mass median aerodynamic particle size of 3.1 ± 1.9 μm was 

stable over the entire exposure period. The animals were exposed 6 h/day, 5 days/week, 

except holidays, for two years. Group sizes in the studies were four mature adult 

monkeys per sex per control and exposed groups, and 150 rats per sex per control and 

exposed groups. In life parameters evaluated for monkeys and rats included weekly 

clinical observation, blood and clinical chemistry analyses prior to exposure and at 1, 3, 

6, 12, 18, and 24 months, and comprehensive eye examinations at the same intervals 

that blood chemistries were conducted. Ten rats/sex/group were pre-selected for 

cytogenetic evaluation (results presented below under Section 7.1.3.2 for in vivo

genotoxicity) at five days, 12 months and 24 months of exposure; however due to high 

mortality in control and exposed groups, only five to eight rats per group were evaluated 

at 22 months, rather than 24 months. For rats, interim sacrifices were conducted at 5 

days, 1, 3, 6, 12 and 18 months with terminal sacrifice at 24 months. Fasting body 

weights and the weights of heart, lung plus trachea, liver, gonads, adrenals, 

thyroid/parathyroids, kidneys, spleen and brain were recorded at each scheduled 

necropsy. Thirty-one designated tissues from ten rats/sex in the control and high 

exposure groups were examined microscopically after 3,6,12 and 18 months; all 

remaining animals from control and high exposure level groups were evaluated after 24 

months of exposure. All animals sacrificed in extremis or found dead were also 

evaluated. Only lung plus trachea (at 12, 18 and 24 months) and nasal turbinates (at 24 

months) were examined microscopically from rats in the 10 mg/m3

 exposure group. All 

monkeys were sacrificed after 24 months of exposure. The same 31 tissues were 

evaluated microscopically in control and high dose groups; weights for the same organs 

listed for rats were also obtained. Again, only lung plus trachea and nasal turbinates were 

microscopically evaluated for monkeys in the 10 mg/m3

 exposure group. There were no 

treatment-related effects on body weights or mortality in rats or monkeys. 

The only treatment-related effects reported from these chronic studies were for the lungs 

in both rats and monkeys. There were dose-related increases in lung plus trachea 

weights and inflammatory changes in the lungs in rat and monkey petroleum coke 

exposed groups, accompanied by pigment accumulation (presumed to be test material) 

in the lung and associated lymph nodes. The lung histological changes in treated rats 

included pulmonary interstitial inflammatory responses with focal fibrosis, 

bronchiolization, sclerosis, squamous alveolar metaplasia and the presence of keratin 

cysts. The keratin cysts were considered to be an advanced stage of squamous alveolar 

metaplasia but were not considered to be an oncogenic response. The severity of the rat 

histological changes was related to the duration and concentration of exposure, and was 

considered to be non-reversible. These lung effects in the rat are considered a nonspecific response of the lung to high concentrations of insoluble particles rather than 

compound specific induced effects, also referred to as rat lung particle overload, and are 

unlikely to be relevant to humans (Snipes, 1995; Mauderly and McCunney, 1996). By 

contrast, the primates exhibited lung and pulmonary lymph node pigment accumulation 

(presumed to be test material) at both exposure levels as a result of phagocytosis by 

pulmonary macrophages; however, inflammatory or metaplastic changes, as observed in 

the rats, were absent. Petroleum coke was not found to be carcinogenic by the inhalation 

route in either the rat or monkey study. In both rats and monkeys, the portal of entry 

LOAEL was < 10 mg/m3

, and the systemic toxicity NOAEL was > 30 mg/m3. 

13 
Although not a guideline repeated-dose toxicity study, the OECD 421 

Reproductive/Developmental Toxicity Screening Test (described in Section 7.1.4) 

provides additional evidence for the conclusion that petroleum coke has low repeateddose toxicity. Male and female Sprague-Dawley rats (12/sex/group) were exposed via 

nose-only inhalation to 0, 30, 100 or 300 mg/m3

 micronized green coke with an average 

mass median aerodynamic diameter of 2.29 μm. All rats were exposed for 6 h/day, 7 

days/week for 2 weeks prior to mating. Males continued to be exposed for 28 days during 

the mating and post-mating periods. During the mating period, females were exposed 

until evidence of mating was observed or for 14 consecutive days. Once mated, female 

rats were treated daily during gestation (days 0-19) until euthanized on post-natal day 4. 

Viability, clinical observations, body weights, feed consumption, organ weights, 

macroscopic and microscopic findings were evaluated. The only exposure-related effects 

observed were portal-of-entry effects in the respiratory tract and associated lymphatic 

system effects (see Reproductive and Developmental section below). No systemic toxic 

effects were observed. 

Additional support for the determination of low repeated-dose toxicity of petroleum coke 

is provided by a lifetime mouse dermal carcinogenicity study conducted on four samples 

of green coke and related substances (delayed process coke; fluid process coke; solid 

condensed emissions from delayed coke process; and process water from delayed 

process coke). Each of the petroleum coke samples was micronized and suspended in 

mineral oil, and applied to mouse skin three times per week for two years (Wingate and 

Hepler, 1982). Particle size was not provided in the assay or analytical reports. However, 

rough measurements based on scanning electron micrographs of the micronized 

particles indicate that particle size was uniform and approximately < 5 μm in diameter. 

Groups of 25 male and 25 female C3H/HeJ mice were treated three times per week with 

100 μl of 250 mg/mL test material dissolved in mineral oil. Body weights were taken once 

every two weeks, and clinical observation were made three times per week. Mice that 

died or were sacrificed in a moribund condition were necropsied and examined for 

occurrence of neoplasms in the viscera. Histological examination was limited to site of 

application and neoplasms found at necropsy. There were no treatment-related effects on 

survival or body weights. The number of visceral masses and other masses (other than 

treatment site) in the treated animals were comparable to controls. The only effect 

observed in the mice was a thickening of the skin in the area of treatment. None of the 

coke samples caused skin cancer in this study. 

Conclusion: The repeated-dose inhalation and dermal toxicity studies indicate low 

systemic toxicity for green coke. In the inhalation studies there were portal-of-entry 

inflammatory changes in the lung attributed to non-specific particle burden, rather than a 

specific response to petroleum coke. Based on results of the two-year studies in rats and 

monkeys, the inhalation repeated-dose portal-of-entry LOAEL was < 10 mg/m3

, and the 

systemic NOAEL was > 30 mg/m3

. 

7.1.3. Genetic Toxicity 

7.1.3.1. In Vitro 

Both delayed and fluid process green coke were evaluated for bacterial mutagenicity in 

the standard bacterial mutagenesis test using Salmonella typhimurium strains TA 1535, 

1537, 1538, 98 and 100, with and without metabolic activation (S-9 from Aroclor 1254-

induced Sprague-Dawley rats). The solvent used in these studies was dimethyl sulfoxide 

(DMSO). None of the coke samples produced a positive response in any of the tested 

strains at concentrations up to 10,000 μg/0.1 mL (Hazleton, 1981 a, b). 

As part of a workplace study on PAH concentrations and mutagenicity of petroleum coke, 

petroleum pitch, and airborne particulate matter, Monarca et al. (1982) tested petroleum 

14 
coke in Salmonella typhimurium strains TA 98 and TA 100. Petroleum coke was ground 

in a mortar, then 50 grams were sequentially extracted with four solvents of increasing 

polarity (benzene, chloroform, methanol and acetone). Samples were taken at each 

extraction step, dried, weighed and dissolved in DMSO. The non-extractable residual 

material (99.71% of starting material) was also tested as a DMSO suspension. The five 

samples (four extraction steps & the non-extractable residue) were tested for mutagenic 

potential in TA 98 and TA 100 at 0.1 – 4 mg/plate with and without metabolic activation 

(liver S-9 from Aroclor 1254 induced male Sprague-Dawley rats). The criteria for a 

positive response were defined as the observations of a dose-related response and a 

three-fold or higher increase in revertants per plate as compared to controls. By these 

criteria, no mutagenic activity was observed in any of the coke solvent fractions or nonextractable residue. 

Green coke (sponge-form delayed process; same sample as used in the rat and monkey 

two-year studies described in Section 7.1.2) was evaluated in a modified bacterial 

mutagenicity assay (Dalbey et al., 1998; ASTM International, 2004b). It has been shown 

previously that the standard bacterial assay is insensitive to certain classes of materials, 

including petroleum substances (Blackburn et al., 1984; 1986). In the modified assay, 

samples are typically dissolved in cyclohexane and subsequently extracted with dimethyl 

sulfoxide (DMSO) to produce aqueous compatible solutions which readily interact with 

tester bacteria. Additionally, hamster, rather than rat, liver homogenate (S-9) is used, and 

only one bacterial strain tested, Salmonella typhimurium TA 98. In this particular study, 

200 mg green coke was extracted with 1 ml DMSO and the extract tested with metabolic 

activation. Green coke was positive in this assay with a mutagenicity index of 12.5. 

Jongeneelen et al. (1989) tested four petroleum coke samples in a bacterial mutagenicity 

assay. Samples were sonicated in DMSO for 30 minutes, and the resultant suspension 

tested in Salmonella typhimurium strains TA 98 and TA 100 in the absence and presence 

of Aroclor 1254-induced S-9 metabolizing system. All four petroleum coke samples 

demonstrated a concentration-related doubling of the number of revertants as compared 

to controls in both tester strains in the presence of S-9 (species of origin not specified), 

and were therefore considered to be mutagenic by the study authors. 

Delayed and fluid process coke samples were also evaluated in a mammalian cell 

mutagenicity test using the L5178Y mouse lymphoma cells (Hazleton, 1981 a, b). The 

tests were conducted on DMSO extracts of coke with and without metabolizing enzymes 

in the assay system (S-9 from polychlorinated biphenyl-induced Sprague-Dawley rats). 

Neither coke sample was mutagenic. 

Conclusion: Green coke was not mutagenic in standard in vitro genetic toxicity tests in 

bacteria and mammalian cells. However, when tested in a modification of the standard 

bacterial assay developed for petroleum substance testing, DMSO extracts of petroleum 

coke were mutagenic in the Salmonella mutagenicity assay. 

7.1.3.2. In Vivo

Fluid process green coke was evaluated for its ability to produce chromosome 

aberrations in a bone marrow cytogenetic assay (Hazleton, 1981b). Male SpragueDawley rats were exposed via inhalation to concentrations of 0, 10 and 40 mg/m3

petroleum coke with a particle size of less than 5 μm. Rats in the 10 mg/m3

 group were 

exposed 6 h/day, 5 days/week for a total of 20 exposures. Rats in the 40 mg/m3

 were 

exposed 6 h/day for 5 days only. Control rats were held for the full 28 days of the study 

before assessment. The day after the last exposure, colchicine was administered to 

inhibit mitosis and bone marrow was subsequently analyzed for chromosomal changes. 

There were no treatment-related chromosomal effects in any treatment group as 

compared to controls. Fluid process coke was not genotoxic in this study. 

15 
Delayed process green coke was evaluated for its ability to produce chromosome 

aberrations in a bone marrow cytogenetic assay (Hazleton, 1981a). Male SpragueDawley rats were exposed via inhalation to concentrations of 0, 10 and 40 mg/m3

petroleum coke with a particle size of less than 5 μm. Rats in the 10 mg/m3

 exposure 

group were exposed 6 h/day, 5 days/week for a total of 20 exposures. Rats in the 40 

mg/m3

 were exposed 6 h/day for 5 days only. Control rats were held for the full 28 days 

of the study before assessment. The day after the last exposure, colchicine was 

administered to inhibit mitosis and bone marrow analyzed for chromosomal changes. 

There were no treatment-related chromosomal effects in the 10 mg/m3

 exposure group. 

In the 40 mg/m3

 exposure group, there were significant increases in the number of 

chromatid breaks, markers and total aberrations as compared to controls. The laboratory 

later determined that the slides had been inconsistently evaluated and misread in some 

cases. This study was therefore considered to be technically flawed and inconclusive. 

To resolve uncertainty, a third in vivo cytogenetics study was conducted on bone marrow 

from male and female rats in the chronic inhalation study described in Section 7.1.2. 

(IRDC, 1985; Klonne et al., 1987). Analysis was conducted on male and female 

Sprague-Dawley rats after exposure for five days, 12 months and 22 months to 

concentrations of 0, 10 and 30 mg/m3

 delayed process green coke dust. There were no 

significant differences from controls in chromosomal aberrations in any exposed animals 

at any of the three time points. Delayed process petroleum coke was not genotoxic under 

these test conditions. 

Conclusion: The weight of the evidence from these three studies indicates that green 

coke was not genotoxic in in vivo bone marrow chromosome cytogenetic assays. 

7.1.4. Reproductive and Developmental Toxicity 

An OECD 421 Reproductive/Developmental Toxicity Screening Test (OECD, 1995) was 

conducted on delayed process green coke (HLS, 2006). A two-week range finding study 

was conducted to select exposure levels for the definitive study. Male and female 

Sprague-Dawley rats (12/sex/group) were exposed via nose-only inhalation to 0, 30, 100 

or 300 mg/m3

 micronized green coke with an average mass median aerodynamic 

diameter of 2.29 μm. All rats were exposed for 6 h/day, 7days/week for 2 weeks prior to 

mating. Males continued to be exposed for 28 days during the mating and post-mating 

period. During the mating period, females were exposed until evidence of mating was 

observed or for 14 consecutive days. Once mated, female rats were treated daily during 

gestation (days 0-19) until euthanized on post-natal day 4. Viability, clinical observations, 

body weights, feed consumption, survival, organ weights, macroscopic and microscopic 

findings were evaluated in parental rats. Standard reproductive (mating indices, 

pregnancy rates, male fertility indices, gestation length, number of implantation sites and 

corpora lutea, pre- and post-implantation loss, pups per liter, live born and stillborn pups, 

and incidence of dams with no viable pups) and developmental (pup physical 

examination, viability, weight, sex ratio, liter survival indices, and mean pup survival 

indices) endpoints were evaluated. 

The only exposure-related parental effects observed were portal-of-entry effects in the 

respiratory tract and associated lymphatic system effects. Lungs from all test substancetreated rats were slightly to severely discolored black. Lung weights were increased in a 

dose-related manner up to 37% in males and 58% in females. Inhalation of petroleum 

coke was associated with the presence of pigment deposits (presumed to be test 

material) in the lungs, mediastinal lymph nodes and nasal olfactory epithelium of most 

male and female rats, and in the lumens of the nasal turbinates and pharynx of male rats. 

Test substance-related changes characterized by proliferative and/or inflammatory 

responses were observed in the lungs in all test substance-exposed rats. In the 

mediastinal lymph nodes draining the lungs, hyperplasia of the paracortical T lymphocyte 

16 
population accompanied the deposition of pigment. In the larynx, minimal squamous 

metaplasia of the respiratory epithelium was also observed. These effects were 

considered non-specific responses to high concentrations of insoluble particles rather 

than compound-specific induced effects (Snipes, 1995). A parental portal-of-entry 

NOAEL could not be determined since effects were observed at the lowest exposure. 

The parental portal-of-entry LOAEL was < 30 mg/m3

, the lowest concentration tested. 

No parental systemic or reproductive toxicity was observed in either sex. There were no 

treatment-related effects on the offspring. The parental systemic, reproductive, and 

developmental NOAELs were > 300 mg/m3

. 

Conclusion: Based on the OECD 421 Reproductive/Developmental Toxicity Screening 

Test, petroleum coke demonstrated low reproductive and developmental toxicity. 

Parental systemic toxicity, reproductive toxicity, and developmental toxicity NOAELs were 

>300 mg/m3

, which was the highest concentration tested. 

7.2. Health Effects Other 

7.2.1. Carcinogenicity 

Petroleum coke was not carcinogenic in three carcinogenicity studies, which have 

already been described in Section 7.1.2 Repeated-dose Toxicity. Rats and monkeys 

were exposed via inhalation five days/week for two years to 0, 10, or 30 mg/m3

 petroleum 

green coke and no excess cancers were observed. In a lifetime skin painting study, mice 

were exposed three times per week to 0 or 100 μl of 250 mg/mL petroleum green coke 

and no excess skin or visceral cancers were observed. Petroleum coke was not 

carcinogenic via the inhalation and dermal routes of administration at the highest 

concentrations tested. 

7.3. Assessment Summary for Health Effects 

Overall, petroleum coke has a low health hazard potential. Green coke is not acutely 

toxic with an acute inhalation toxicity NOAEL estimated to be > 300 mg/m3

. Findings 

observed in inhalation repeated-dose and chronic studies were confined to respiratory 

system (portal-of-entry) inflammatory changes that were attributed to non-specific effects 

of insoluble particles rather than petroleum coke-specific effects. The repeated-dose 

portal-of-entry LOAEL and systemic NOAEL were < 10 mg/m3

 and > 30 mg/m3, 

respectively. Green coke was not mutagenic in vitro in standard bacterial or mammalian 

cell assays. Green coke was mutagenic in modified in vitro bacterial assays developed to 

optimize detection of mutagenicity for certain classes of water-insoluble compounds that 

are negative in the standard bacterial assay. Green coke was not genotoxic in in vivo

bone marrow chromosome cytogenetic assays. Green coke did not induce reproductive 

or developmental toxicity at exposures up to 300 mg/m3

. The reproductive and 

developmental toxicity NOAELs were > 300 mg/m3

. Green coke was not carcinogenic in 

two inhalation studies (rat and monkey; high exposure = 30 mg/m3

) and one mouse 

dermal study (one exposure level only = 100 μl of a 250 mg/ml coke solution). 

Green coke is considered to have a higher potential to induce health effects than calcined 

coke due to green coke having higher levels of volatile matter as compared to calcined 

coke. Green coke testing results have been conservatively extrapolated to calcined coke 

in lieu of testing calcined coke. Results from green coke health testing and extrapolation 

to calcined coke are summarized in Table 3 on the next page. 

17 
8. MATRIX OF PETROLEUM COKE CATEGORY DATA 

Table 3 

PETROLEUM COKE CATEGORY DATA MATRIX 

Endpoint Petroleum Coke (Green) 

CAS # 64741-79-3 

Petroleum Coke 

(Calcined) 

CAS # 64743-05-1 

Physical-Chemical Properties

Melting Point N/Aa N/A 

Boiling Point N/A N/A 

Vapor Pressure N/A N/A 

Partition Coefficient N/A N/A 

Water Solubility N/A N/A 

Environmental Fate 

Photodegradation N/A N/A 

Stability in Water N/A N/A 

Environ. Transport N/A N/A 

Biodegradation N/A N/A 

Environmental Effects 

Acute Fishb LL50 > 1000 mg/L 

NOELR = 1000 mg/L 

LL50 > 1000 mg/L 

NOELR = 1000 mg/L 

Acute Daphnia EL50 > 1000 mg/L 

NOELR = 1000 mg/L 

EL50 > 1000 mg/L 

NOELR = 1000 mg/L 

Algae EL50 > 1000 mg/L 

NOELR < 1000 mg/L 

EL50 > 1000 mg/L 

NOELR < 1000 mg/L 

Terrestrial LC50 > 1000 mg/kg 

NOEC = 1000 mg/kg 

LC50 > 1000 mg/kg 

NOEC = 1000 mg/kg 

Health Effectsc

Acuted LC50 > 300 mg/m3 LC50 > 300 mg/m3

Repeated-Dose 

Systemic 

Portal-of-entry 

NOAEL > 30 mg/m3 

LOAEL < 10 mg/m3

NOAEL > 30 mg/m3 

LOAEL < 10 mg/m3

Genotoxicity, in vitro, bacterial 

 Standard assay 

 Modified assay (optimize organic 

 extractable compounds) 

negative 

positive 

negative 

positive 

Genotoxicity, in vitro, non-bacterial negative negative 

Genotoxicity, in vivo negative negative 

Reproductive toxicity NOAEL > 300 mg/m3 NOAEL > 300 mg/m3

Developmental toxicity NOAEL > 300 mg/m3 NOAEL > 300 mg/m3

Carcinogenicity 

 Inhalation 

 Dermal 

negative 

negative 

negative 

negative a

 N/A indicates that evaluation of endpoint is Not Applicable due to physical-chemical state. 

Technical discussions are presented in text to address these endpoints as appropriate. 

b

 Gray shading indicates category read-across from green coke empirical data to calcined coke. 

c

 Inhalation was the route of exposure unless otherwise indicated. 

d

 Yellow shading indicates values estimated from longer term studies 

18 
9. CATEGORY ANALYSIS CONCLUSIONS 

It is appropriate for green coke and calcined coke to be grouped together in one 

category. This grouping is justified based on their manufacturing processes, which result 

in similar physical chemical characteristics and chemical composition. The hazard 

potential for the petroleum coke category was characterized by summarizing existing 

data, and testing delayed process green coke to fill in the data gaps identified in existing 

data. Green coke is considered to have a higher potential to induce environmental 

and/or human effects than calcined coke due to its higher volatile matter. Therefore, the 

green coke hazard study results have been conservatively extrapolated to calcined coke 

in lieu of testing calcined coke. 

Petroleum coke is a complex mixture of mostly elemental carbon with inorganic and 

organic constituents embedded in the carbon matrix. In general, these constituents do 

not contain the chemical bonds that engage in photolytic or hydrolytic reactions. If 

released to the environment, petroleum coke would be expected to be non-reactive and 

either disperse or remain in the environmental compartment to which it was released. 

Therefore, depending on factors such as particle size and density relationships between 

the petroleum coke and environmental media, releases to terrestrial or aquatic 

environments would result in incorporation of the material in soils/sediments or dispersal 

via wind/water action. Biodegradation would not be an important fate process because 

the majority of the constituents in petroleum coke do not contain the chemical bonds 

needed for microbial metabolism. 

Petroleum coke has an extremely low environmental hazard potential. Petroleum green 

coke demonstrated no effect on aquatic vertebrates and invertebrates, and only a slight 

effect on algae at 1000 mg/L (WAF). Petroleum green coke did not produce any adverse 

effects when tested against terrestrial soil-dwelling invertebrates and vascular plants at 

1000 mg/kg soil. 

Petroleum coke has a low health hazard potential. Green coke is not acutely toxic. The 

acute inhalation toxicity NOAEL was estimated to be > 300 mg/m3

. Findings observed in 

repeated-dose and chronic inhalational toxicity studies were confined to portal-of-entry 

effects that are attributed to non-specific effects of insoluble particles rather than 

petroleum coke-specific effects. The repeated-dose portal-of-entry LOAEL and systemic 

NOAEL were estimated to be < 10 mg/m3

 and > 30 mg/m3, respectively. Green coke was 

not mutagenic in vitro in standard bacterial or mammalian cell assays. Green coke was 

mutagenic in modified in vitro bacterial assays developed to optimize detection of 

mutagenicity for certain classes of compounds that are negative in the standard bacterial 

assay. Green coke was not genotoxic in in vivo bone marrow chromosome cytogenetic 

assays. Green coke did not induce reproductive or developmental toxicity at exposures 

up to 300 mg/m3

. The parental systemic, reproductive, and developmental toxicity 

NOAELs were all > 300 mg/m3

. Green coke was not carcinogenic in two inhalation (rat 

and monkey; highest exposure concentration was 30 mg/m3

) studies and one mouse 

dermal study (one exposure level only equal to100 μl of a 250mg/mL coke solution). 

Based on the data presented in this report, both green coke and calcined coke (using 

read-across from green coke) have a low potential to cause adverse effects to the 

environment, and, with the exception of non-compound-specific, insoluble particle portalof-entry effects, to human health. 

19 
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24 
11. LIST OF ABBREVIATIONS AND ACRONYMS 

API – American Petroleum Institute 

BOD – biological oxygen demand 

Btu/lb – British thermal unit per pound 

Btu/scf – British thermal unit per standard cubic feet 

AUGC – area under the growth curve 

CASRN/CAS #/CAS No. - Chemical Abstract Service Registry Number o

C – degrees Celsius 

CONCAWE – Conservation of Clean Air and Water in Europe 

d - day 

DMSO – Dimethyl sulfoxide 

EINECS – European Inventory of Existing Commercial Chemical Substances 

EL50 – effective loading rate lethal to 50% of the test population 

EbL50 – effective loading rate that causes 50% reduction in algal cell biomass 

ErL50 – effective loading rate that causes 50% reduction in algal growth rate 

EPA/US EPA – United States Environmental Protection Agency 

g/cm3 – grams per cubic centimeter 

h - hour 

HLS – Huntingdon Life Sciences 

HPV – High Production Volume 

IRDC – International Research and Development Corporation 

o

K – degrees Kelvin 

kPa - kilopascal 

LC50 – lethal concentration for 50% of the test population 

LL50 – lethal loading rate for 50% of the test population 

Loading Rate – total amount of test substance added to dilution water to 

 prepare water accommodated fractions (WAFs) for ecotoxicity testing 

LOAEL – lowest observable adverse effect level 

mg/kg – milligrams per kilogram 

mg/L – milligrams per liter 

mg/m3 – milligrams per cubic meter 

mL - milliliter 

mm - millimeter 

nm - nanometer 

NOAEL – no observable adverse effect level 

NOEC – no observable effect concentration 

NOELR – no observable effect loading rate 

OECD – Organization for Economic Cooperation and Development 

OPPTS – US EPA Office of Prevention, Pesticides and Toxic Substances 

PAC - Polycyclic aromatic compound 

PAH – polycyclic aromatic hydrocarbon 

PNA – polynuclear aromatic 

ppm – part per million 

SIDS – Screening Information Data Set 

US EPA – United States Environmental Protection Agency 

UV - ultraviolet 

WAF – water accommodated fraction 

wt% - weight percent 

μg - microgram 

μg/L – microgram/liter 

> greater than 

< less than 

= equal to 

25 
12. GLOSSARY 

NOTE: The following terms are used in this document. To the extent possible definitions were 

taken from relevant authoritative sources such as EPA, OECD, ASTM and IUPAC. 

Bioavailability: The state of being capable of being absorbed and available to interact with the 

metabolic processes of an organism. Typically a function of chemical properties, physical state of 

the material to which an organism is exposed, and the ability of the individual organism to 

physiologically take up the chemical. Also, the term used for the fraction of the total chemical in the 

environmental which is available for uptake by organisms. (AIHA 2000)

Calcined Coke: A petroleum coke or coal-derived pitch coke obtained by heat treatment of 

green coke to about 1600° K. It will normally have a hydrogen content of less than 0.1 wt.%. 

(IUPAC 1995)

Carbonization: The process by which solid residues with increasing content of the element 

carbon are formed from organic material usually by pyrolysis in an inert atmosphere. (IUPAC 

1995)

Catalytic Cracking: The refining process of breaking down the larger, heavier, and more 

complex hydrocarbon molecules into simpler and lighter molecules. Catalytic cracking is 

accomplished by the use of a catalytic agent and is an effective process for increasing the yield of 

gasoline from crude oil. Catalytic cracking processes fresh feeds and recycled feeds. (US DOE 

2007)

Category Member: The individual chemical or substance entities that constitute a chemical 

category. 

Category: A chemical category, for the purposes of the HPV Challenge Program, is a group of 

chemicals whose physicochemical and toxicological properties are likely to be similar or follow a 

regular pattern as a result of structural similarity. These structural similarities may create a 

predictable pattern in any or all of the following parameters: physicochemical properties, 

environmental fate and environmental effects, and/or human health effects. (US EPA 2007)

Dose: The amount of a substance available for interactions with metabolic processes or 

biologically significant receptors after crossing the outer boundary of an organism. The potential 

dose is the amount ingested, inhaled, or applied to the skin. The applied dose is the amount 

presented to an absorption barrier and available for absorption (although not necessarily having 

yet crossed the outer boundary of the organism). The absorbed dose is the amount crossing a 

specific absorption barrier (e.g., the exchange boundaries of the skin, lung, and digestive tract) 

through uptake processes. Internal dose is a more general term denoting the amount absorbed 

without respect to specific absorption barriers or exchange boundaries. The amount of the 

chemical available for interaction by an particular organ or cell is termed the delivered or 

biologically effective dose for that organ or cell (US EPA 2002).

Dose-Response Relationship: The relationship between a quantified exposure (dose) and the 

proportion of subjects demonstrating specific biological changes in incidence or in degree of 

change (response) (US EPA 2002). 

Ecological Effects – all endpoints (OECD definitions) 

Fish, Acute Toxicity Test: In a four-day exposure, acute toxicity is defined by the LC50, 

the concentration of test substance in water which kills 50% of the test population of fish. 

26 
Test methodology is described in OECD Guideline 203, in OECD Guidelines for the 

Testing of Chemicals. 

Daphnia sp., Acute Immobilization Test: In a one or two-day exposure, acute toxicity 

is defined by the EC50, the concentration of test substance in water which causes 

immobilization to 50% of the test population of invertebrates. Test methodology is 

described in OECD Guideline 202, Part 1, in OECD Guidelines for the Testing of 

Chemicals. 

Alga, Growth Inhibition Test: In a three-day exposure, growth inhibition is defined by 

the EC50, the concentration of test substance in growth medium which results in a 50% 

reduction in either alga cell growth or growth rate relative to a control group. Test 

methodology is described in OECD Guideline 201, in OECD Guidelines for the Testing of 

Chemicals. 

Elemental Carbon: Elemental refers to the adjective form of the word, element. Thus for 

example, in chemistry, it refers to matter composed of only one chemical element. Graphite and 

diamond are types of elemental carbon. (Wikipedia 2007a 

http://en.wikipedia.org/wiki/Main_Page)

Endpoint: In the context of the EPA High Production Volume Challenge Program, an endpoint is 

a physical-chemical, environmental fate, ecotoxicity, and human health attribute measurable by 

following an approved test methodology (e.g., OECD Guidelines for Testing of Chemicals). 

Melting point, biodegradation, fish acute toxicity, and genetic toxicity are examples of endpoints 

that are measured by an approved test method. (US EPA 1999) 

Environmental Fate Effects – all endpoints (OECD definitions) 

Photodegradation: The photochemical transformation of a molecule into lower 

molecular weight fragments, usually in an oxidation process. This process may be 

measured by Draft OECD Guideline, “Phototransformation of Chemicals in Water – Direct 

and Indirect Photolysis”. This process also may be estimated using a variety of computer 

models. 

Stability in Water: This environmental fate endpoint is achieved by measuring the 

hydrolysis of the test substance. Hydrolysis is defined as a reaction of a chemical RX 

with water, with the net exchange of the group X with OH at the reaction center. Test 

methodology for hydrolysis is described in OECD Guideline 111, in OECD Guidelines for 

the Testing of Chemicals. 

Transport Between Environmental Compartments: This endpoint describes the 

distribution of a chemical between environmental compartments using fugacity-based 

computer models. The results of the model algorithms provide an estimate of the amount 

of the chemical within a specific compartment. The environmental compartments 

included in many models are air, water, soil, sediment, suspended sediment, and aquatic 

biota. 

Biodegradation: Breakdown of a substance catalyzed by enzymes in vitro or in vivo. As 

an endpoint in EPA’s HPV program, biodegradation is measured by one of six 

methodologies described in OECD Guidelines 301A-F, in OECD Guidelines for the 

Testing of Chemicals. 

Exposure: Contact made between a chemical, physical, or biological agent and the outer 

boundary of an organism. Exposure is quantified as the amount of an agent available at the 

exchange boundaries of the organism (e.g., skin, lungs, gut). (US EPA 2002).

27 
Feedstock: A refinery product that is used as the raw material for another process; the term is 

also generally applied to raw materials used in other industrial processes. (Speight, 2007).

Female Mating Index: Number of females with confirmed mating (sperm and/or vaginal 

plug)/number of females placed with males. (HLS 2006). 

Green coke (raw coke): This is the primary solid carbonization product from high boiling 

hydrocarbon fractions obtained at temperatures below 900° K. It contains a fraction of matter that 

can be released as volatiles during subsequent heat treatment at temperatures up to 

approximately 1600° K. This mass fraction, the so-called volatile matter, is in the case of green 

coke between 4 and 15%, but it depends also on the heating rate. (IUPAC 1995).

Hazard Assessment: The process of determining whether exposure to an agent can cause an 

increase in the incidence of a particular adverse health effect (e.g., cancer, birth defect) and 

whether the adverse health effect is likely to occur in humans (US EPA 2002). 

Hazard Characterization: A description of the potential adverse health effects attributable to a 

specific environmental agent, the mechanisms by which agents exert their toxic effects, and the 

associated dose, route, duration, and timing of exposure (US EPA 2002).

Hazard: A potential source of harm (US EPA 2002). 

Health Effects – all endpoints (OECD definitions, unless otherwise specified) 

Acute Toxicity: The adverse effects occurring within a short time-frame of 

administration of a single dose of a substance, multiple doses given within 24 hours, or 

uninterrupted exposure over a period of 24 hours or less. Exposure may be via oral, 

dermal or inhalation routes as described in OECD Guidelines 401, 402, 403, and 420 in 

OECD Guidelines for the Testing of Chemicals. 

Developmental Toxicity: Adverse effects on the developing organism that may result 

from exposure prior to conception (either parent), during prenatal development, or 

postnatally until the time of sexual maturation. The major manifestations of 

developmental toxicity include death of the developing organism, structural abnormality, 

altered growth, and functional deficiency. (US NLM 2007) 

Genetic Toxicity in vivo (Chromosomal Aberrations): The assessment of the 

potential of a chemical to exert adverse effects through interaction with the genetic 

material of cells in the whole animal. Genotoxicity may be studies in the whole animal 

using methods described in OECD Guideline 475, in OECD Guidelines for the Testing of 

Chemicals. 

Genetic Toxicity in vitro (Gene Mutations): The assessment of the potential of a 

chemical to exert adverse effects through interaction with the genetic material of cells in 

cultured mammalian cells. Genotoxicity may be studies in cultured cells using methods 

described in OECD Guideline 476, in OECD Guidelines for the Testing of Chemicals. 

Repeated Dose Toxicity: The adverse effects occurring due to repeated doses that 

may not produce immediate toxic effects, but due to accumulation of the chemical in 

tissues or other mechanisms, produces delayed effects. Repeated dose toxicity may be 

studied following methods described in OECD Guidelines 407, 410, or 412 in OECD 

Guidelines for the Testing of Chemicals. 

Reproductive Toxicity: The occurrence of biologically adverse effects on the 

reproductive systems of females or males that may result from exposure to 

environmental agents. The toxicity may be expressed as alterations to the female or male 

28 
reproductive organs, the related endocrine system, or pregnancy outcomes. The 

manifestation of such toxicity may include, but not be limited to, adverse effects on onset 

of puberty, gamete production and transport, reproductive cycle normality, sexual 

behavior, fertility, gestation, parturition, lactation, developmental toxicity, premature 

reproductive senescence, or modifications in other functions that are dependent on the 

integrity of the reproductive systems. (US EPA 1996f) 

Heavy Petroleum Process Streams: Petroleum streams boiling higher than approximately 

650o

F (345oC), including distillation residues and the absence of low-boiling components. (Altgelt 

and Boduszynski 1994). 

Lowest-Observed-Adverse-Effect Level (LOAEL): The lowest exposure level at which there 

are statistically or biologically significant increases in frequency or severity of adverse effects 

between the exposed population and its appropriate control group (US EPA 2002). 

No-Observed-Adverse-Effect Level (NOAEL): The highest exposure level at which there are 

no biologically significant increases in frequency or severity of adverse effects between the 

exposed population and its appropriate control group; some effects may be produced at this level, 

but they are not considered adverse or precursors to adverse effects (US EPA 2002). 

Petroleum (crude oil): A naturally occurring mixture of gaseous, liquid, and solid hydrocarbon 

compounds usually found trapped deep underground beneath impermeable cap rock and above 

a lower dome of sedimentary rock such as shale; most petroleum reservoirs occur in sedimentary 

rocks of marine, deltaic, or estuarine origin (Speight 2007). 

Petroleum Coke: A solid, carbonaceous residue produced by thermal decomposition of heavy 

petroleum fractions or cracked stocks, or both (ASTM 2005). 

Polycyclic aromatic compound (PAC): PAC includes multi-ringed aromatic hydrocarbons in 

which one or more atoms of nitrogen, oxygen or sulfur (a heteroatom) replace one of the carbon 

atoms in a ring system. The PACs can be grouped according to the heteroatom they contain. 

(API 2007)

Polycyclic Aromatic Hydrocarbon (PAH): A fused aromatic-ring compound consisting only of 

carbon and hydrogen. Similar compounds include chrysene, pyrene, benzo[a]pyrene, perylene, 

etc. Naphthalene, the simplest PAH consists of two fused benzene rings. (API 2007]

Polynuclear Aromatic (PNA): This term is an obsolete term that is not recognized as valid by 

either the International Union on Pure and Applied Chemistry or the American Chemical Society. 

Historically, the term was used to describe the multi-ringed aromatic hydrocarbons now called 

PAHs. (API 2007]

Portal-of-Entry Effect: A local effect produced at the tissue or organ of first contact between the 

biological system and the toxicant (US EPA 1994). 

Read Across: Read-across can be regarded as using data available for some members of a 

category to estimate values (qualitatively or quantitatively) for category members for which no 

such data exist. (OECD 2007)

Residues: Residues, also called residua or resids, are those fractions which are non-distillable 

under given conditions and remain at the bottom of a distillation tower. (Altgelt and 

Boduszynski 1994). 

Systemic Effects or Systemic Toxicity: Toxic effects as a result of absorption and distribution 

of a toxicant to a site distant from its entry point (US EPA 2002). 

29 
Target Organ: The biological organ(s) most adversely affected by exposure to a chemical or 

physical agent (US EPA 2002).

Thermal Cracking: A refining process in which heat and pressure are used to break down, 

rearrange, or combine hydrocarbon molecules. Thermal cracking includes gas oil visbreaking, 

fluid coking, delayed coking, and other thermal cracking processes (e.g., flexicoking). (US DOE 

2007)

Thermal Decomposition: Thermal decomposition is a chemical reaction where a chemical 

substance breaks up into at least two chemical substances when heated. [Wikipedia 2007b 

http://en.wikipedia.org/wiki/Main_Page]

Volatile Matter: The mass loss on heating expressed as a percent loss of the moisture free 

sample used. Samples having a thermal history above 600o C are excluded. Volatile matter is 

determined by measuring the mass loss of the coke when heated under the exact conditions of 

the ASTM standard method D 6374 – 99). To ensure the sample is moisture free it is dried to a 

constant weight at 95 to 105o C prior to the procedure. The procedure involves heating the 

sample to 950 ± 20 o C for five minute periods to constant mass (± 0.5 mg) (ASTM 2004a).

30 
31 

APPENDIX A - Category Members 

CAS No. EINECS No. 

64741-79-3 265-080-3 

Coke (petroleum) 

A solid material resulting from high temperature treatment of petroleum fractions. It 

consists of carbonaceous material and contains some hydrocarbons having a high 

carbon-to-hydrogen ratio (API, 1985). 

64743-05-1 265-210-9 

Coke (petroleum), calcined 

 A complex combination of carbonaceous material including extremely high molecular 

 weight hydrocarbons obtained as a solid material from the calcining of petroleum coke at 

 temperatures in excess of 1,000o

C (1800oF). The hydrocarbons present in calcined coke 

 have a very high carbon-to-hydrogen ratio (API, 1985). 
APPENDIX B – Composition of Green Coke Samples Used in Toxicology Studies 

Delayed Process Green Coke - 2003 

Sample 1 API Sample # 4-1-140 2 Micronized Delayed 

Coke – 1981 

Sample 

pellet 

(initial)4

pellet 

(final)5

micronized 

(initial) 

micronized 

(final) 

Delayed Process 

Coke 1981 Analysis 

Average Mass Median Aerodynamic Particle Size, μm 2000* 2000* 2.3/3.3* 

≤ 5** 3.1 

Elemental Analysis, % wt Carbon 89.93 89.97 Hydrogen 3.71 5.04 Oxygen 1.3 1.62 Sulphur 7.4 5.8 3.36 3.27 Nitrogen 1.1 1.1 Other Analysis, % wt SiO2 0.04 <0.04 Ash 0.21 0.19 Trace Metals, ppm Al (aluminum) 321 205.1 300.2 250.7 As (arsenic) <19.3 <2.3 <29.6 <2.3 <0.001 0.3 B (boron) <19.3 <29.6 Ba (barium) <19.3 7.74 <29.6 6.9 Be (beryllium) <9.6 <14.8 

32 
Delayed Process Green Coke - 2003 

Sample 1 API Sample # 4-1-140 2 Micronized Delayed 

Coke – 1981 

Sample 

pellet 

(initial)4

pellet 

(final)5

micronized 

(initial) 

micronized 

(final) 

Delayed Process 

Coke 1981 Analysis 

Bi (bismuth) <19.3 <29.6 Ca (calcium) 178 81.7 121.6 158.7 Cd (cadmium) <9.6 <14.8 Co (cobalt) <9.6 1.9 <14.8 1.7 Cr (chromium) <9.6 3.9 <14.8 4.6 Cu (copper) <11.6 1.8 <17.8 2.3 Fe (iron) 310 215.9 247 276.1 Hg (mercury) <1 <1 K (potassium) <28.9 10.9 <44.4 20.5 Li (lithium) <9.6 <1.2 <14.8 <1.16 Mg (magnesium) 77.4 50.3 60.9 65.5 Mn (manganese) <19.3 5.3 <29.6 7.3 Mo (molybdenum) <19.3 16.7 <29.6 16.0 Na (sodium) 133 87.8 114.6 99.0 Ni (nickel) 367.1 319.6 351.7 304.6 95 78 P (phosphorus) <19.3 19.8 30.3 25.0 Pb (lead) <19.3 4.88 <29.61 7.4 Pd (palladium) <6.9 <6.9 Pt (platinum) 3.8 4.5 S (sulfur) 73920 58060 Sb (antimony) <48.2 <74.0 Se (selenium) <19.3 <29.6 4.5 <0.2 Si (silicon) 743.2 86.75 204 Sn (tin) <28.9 <2.3 <2.3 

33 
Delayed Process Green Coke - 2003 

Sample 1 API Sample # 4-1-140 2 Micronized Delayed 

Coke – 1981 

Sample 

pellet 

(initial)4

pellet 

(final)5

micronized 

(initial) 

micronized 

(final) 

Delayed Process 

Coke 1981 Analysis 

Ti (titanium) 12.9 11.7 <14.8 14.4 V (vanadium) 1938 1559 1805 1580 145 140 Zn (zinc) 12.0 8.9 <14.8 11.2 Benzene Extract, % wt 1.79 2.08 PAHs, ppm Naphthalene 3.6 3.6 11 11 1-methyl naphthalene 2.7 3.1 10 12 2-methyl naphthalene 11 12 26 26 Acenaphthene ND 0.18 ND 0.51 Acenaphthylene ND 0.12 ND 0.5 Fluorene 0.34 0.37 1.5 1.5 11 ND Phenanthrene 0.69 0.64 7.8 8.2 ND ND Anthracene ND 0.29 3.3 3.6 Pyrene 1.3 1.2 8.6 10 ND 165 Fluroanthene ND 0.1 1.4 1.6 Benzofluorenes ND ND Benzo(a)anthracene 0.58 0.59 7.1 8 544 Benzp(a,b)anthrcene 280 Chrysene 0.88 1.1 9.4 10 126 210 Benzo(a)pyrene 1.8 1.7 11 13 440 175 Benzo(e)pyrene 110 85 Beno(b)fluoranthene 0.52 0.62 3.8 3.9 ND ND Benzo(k)fluoranthene ND ND ND 1.5 

34 
Delayed Process Green Coke - 2003 

Sample 1 API Sample # 4-1-140 2 Micronized Delayed 

Coke – 1981 

Sample 

pellet 

(initial)4

pellet 

(final)5

micronized 

(initial) 

micronized 

(final) 

Delayed Process 

Coke 1981 Analysis 

Perylene ND Methyl benzo(a)pyrene ND ND Benzo(g,h,i)perylene 1.1 1.4 8.7 12 439 120 Dibenzo(a,h)anthracene 0.49 0.51 4.1 4.3 ND NQ Benzo(g,h,i)fluoranthene ND ND Indeno(1,2,3-cd)pyrene 0.34 0.45 3.5 3.3 Dimethylbenz(a)anthracene Methylbenzo(g,h,i)perylene Coronene ND ND Toxicology study(s) in which samples were used: 1 OECD 203 Fish acute toxicity test; OECD 202 Invertebrate acute toxicity test; OECD 201 Algal growth inhibition test; 

Seedling emergence and growth of terrestrial plants; OECD 207 Earthworm acute toxicity test; OECD 421 Reproduction/developmental toxicity screening test 2 Mouse dermal carcinogenicity study; Salmonella assay; mouse lymphoma cell assay 3 Rat chronic inhalation study; Monkey chronic inhalation study; Salmonella assay; Rat in vivo cytogenicity assay 4 initial refers to analyses conducted prior to initiation of the toxicology studies 5 final refers to analyses conducted following completion of the toxicology studies 

ND = not detected NQ = detected, but not quantifiable Blank cells = analysis not performed * values are average mean particle size ** size not measured; value estimated from scanning electron micrographs References: Aveka, Inc., 2003; CONCAWE, 1993; Chevron Products Company, 2003, 2005; Lancaster Laboratories, Inc.

35