l.'nttcd Slates
Agency
Office 01 Research and
Development
Washington, IX" 20460
&EPA Characterizing Risk
at Metal Finishing
Facilities
Meeting the Needs of
All Stakeholders
An EPA Reinvention Initiative
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CHARACTERIZING RISK AT METAL FINISHING FACILITIES
27 January 1998
Dennis J. Brown, Ph.D.
Parsons Engineering Science, Inc.
2101 Webster Street, Suite 700
Oakland, CA 94612
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A draft of this report was prepared during the author's tenure as a Fellow under the
American Association for the Advancement of Science/U.S. Environmental Protection Agency
Fellowship Program during the summer of 1997. Since that time significant changes have been
made to the report in response to comments received from technical reviewers both from -within
and from outside of EPA. The views expressed herein are entirely the author's and do not
represent official policy of either the EPA or AAAS. The report is subject to further review and
revision. Mention of trade names of commercial products does not constitute endorsement or
recommendation.
ACKNOWLEDGMENTS
The author wishes to thank the AAAS and the EPA for providing the opportunity to pursue
the work described herein and for supporting the 10-week Summer Environmental Science and
Engineering Fellowship Program. The author also wishes to thank his mentor, Paul Shapiro, for
his guidance, helpful discussions, and review of the work both during and after the fellowship
period. The author is grateful to the following persons who provided assistance during the
fellowship: Babasaheb Sonawane and the staff of EPA's National Center for Environmental
Assessment for providing technical support and the resources to conduct this work; Michael
Callahan, John Schaum, and Herman Gibb for reviewing and commenting on various versions of
this document; Peter Gallerani, for discussing his work on metal finishing facility emissions and
for arranging a tour of the B.F. Goodrich metal finishing operation in Vergennes, Vermont;
Ronald Vezzi, B.F. Goodrich Process Engineer; Karen Morehouse, EPA Fellowship Coordinator;
and Claudia Sturges, AAAS Fellowship Program Manager. The author is grateful to the National
Metal Finishing Resource Center for providing information on the metal finishing industry.
Among those who provided useful comments on the earlier draft report the author wishes
to thank Caroline Freeman and William Perry, Occupational Safety and Health Administration;
Amy Vasu and Ted Palma, EPA, Office of Air Quality Planning and Standards; Peter Preuss and
Richard Walentowicz, EPA, ORD, National Center for Environmental Research and Quality
Assurance; Dean Menke, 1997/1998 AAAS/EPA Risk Assessment Fellow; Chris Branson,
National Institute of Standards and Technology/Industrial Technology Institute Manufacturing
Extension Center; and Joel Barnhart, American Chrome and Chemicals Company and the Chrome
Coalition.
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TABLE OF CONTENTS
Page
ABSTRACT v
1. INTRODUCTION 1
1.1 NEW APPRO ACHES TO ENVIRONMENTAL PROTECTION 1
1.2 THE METAL FINISHING INDUSTRY 2
1.3 COMMON SENSE INITIATIVE 3
1.4 PROJECT OBJECTIVES 8
2. RISK ASSESSMENT FOR METAL FINISHING FACILITIES 9
2.1 THE RISK ASSESSMENT PROCESS 9
2.1.1 Hazard Identification 11
2.1.2 Dose-Response Assessment 13
2.1.3 Exposure Assessment 18
2.1.4 Risk Characterization 22
2.2 ASSESSING RISK FOR CHROMIUM ELECTROPLATING FACILITIES 25
2.2.1 Hazard Identification 25
2.2.2 Dose-Response Values for Hexavalent Chromium 25
2.2.3 Exposure Assessment 27
2.2.4 Risk Characterization 32
2.3 RISK COMMUNICATION 34
3. SUMMARY 36
4. REFERENCES 37
ACRONYMS 41
APPENDIX A Output from Risk Assistant™ A-l
111
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TABLES
No. Page
1-1 Chemical Substances Potentially Used in, Generated by, or Emitted from
Metal Finishing Facilities 4
2-1 Principle Steps of the Risk Assessment Process for Metal Finishing Facilities 12
2-2 Published EPA Human Health Toxicity Values for Chemical Substances
Potentially Emitted by Metal Finishing Processes 15
2-3 Exposure Assessment Data Needs for Metal Finishing Facilities 19
2-4 Generalized Dose Equations 20
2-5 Environmental Concentrations of Hexavalent Chromium Used in the
Example Risk Assessment 27
2-6 Summary of Exposure Factors Used in Example Risk Assessment 28
2-7 Relative Proportion of Hexavalent Chromium Concentrations Measured
in the Workplace 29
2-8 Predicted Lifetime Excess Cancer Risks and Hazard Quotients
for Exposure to Hexavalent Chromium 33
FIGURES
No. Page
1-1 Metal Finishing Sector Organization Within the Common Sense Initiative 5
2-1 The Risk Assessment/Risk Management Paradigm 9
2-2 Conceptual Exposure Model for Electroplating Process 18
2-3 Exposure Scenarios for Workers .- 30
2-4 Exposure Scenarios for Residents 31
2-5 Lifetime Excess Cancer Risk for Community Residents for
Example Risk Assessment 34
IV
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ABSTRACT
Facility-based risk characterization for workers and surrounding communities is a high
priority issue for stakeholders in the Environmental Protection Agency's Common Sense Initiative
Metal Finishing Sector. Platers, environmental groups, community groups, labor, and regulators
all need and want to know what emissions are coming out and in what amounts from metal
finishing operations. They also want to know what health risks those emissions create for
workers and the surrounding communities.
A process is described herein that includes a problem formulation phase to identify the types
and forms of information that are wanted by the different stakeholders and a risk assessment
phase to quantify the health risks associated with facility emissions. A screening level risk
assessment is performed in which toxicity information and exposure data are used to show how a
facility-based risk assessment could be performed for a typical electroplating operation.
Information needs for a more refined assessment are presented.
A single iteration of the problem formulation and risk assessment processes may lead
directly to a risk management decision or the steps may be modified and repeated, taking into
account input from stakeholders obtained during the risk communication process. Uncertainties
associated with toxicity information and exposure scenarios will present challenges for providing
simple (but not simplistic) methods of risk assessment that can be applied by facility operators,
community groups, and other stakeholders. This type of risk characterization is not only desired
but possible to carry out for a variety of exposure scenarios.
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1. INTRODUCTION
The mission of the United States Environmental Protection Agency (EPA) is to protect and
improve the quality of public health and the environment. As applied to industrial sources of
pollution, this mission has been carried out primarily through the development and implementation
of policies and programs to reduce or prevent releases of chemicals to the environment. Many of
these policies and programs focus on media-specific (i.e., air, water, soil) controls on emissions
through the authority granted the EPA by various regulatory statutes (e.g., the Clean Air Act, the
Clean Water Act, and the Resource Conservation and Recovery Act). The EPA and others have
recently suggested that the current regulatory system, which uses a chemical-by-chemical,
medium-by-medium, risk-by-risk approach to assess and reduce environmental health risks, be
modified to consider health and environmental effects of pollutants in their broader context, which
often includes emissions to more than one medium and/or exposures of multiple populations (e.g.,
on-site workers, the public) (Browner, 1994; Presidential/Congressional Commission on Risk
Assessment and Risk Management, 1997a, 1997b).
1.1 NEW APPROACHES TO ENVIRONMENTAL PROTECTION
To aid in the development and assessment of new approaches to environmental protection,
EPA has sought input from persons who may be affected by any change in EPA's regulatory
process through programs such as the Common Sense Initiative (CSI) and Project XL. These
persons (stakeholders) may include representatives from industry, workers, trade organizations,
community groups, environmental justice groups, environmental groups, and state and local
governments. It is EPA's stated purpose to use the input from these groups to reinvent the way
that it accomplishes environmental protection (Browner, 1994). One form that reinvention has
taken is to move away from "command-and-control" policies toward the greater use of
performance-based approaches that reward environmental excellence as much as they punish non-
compliance (EPA, 1997b). The EPA has developed several pollution prevention programs that
encourage industry to reduce the quantity of hazardous chemicals released to the environment by
substituting less toxic chemicals in their operations, by using smaller quantities of chemicals, or by
recycling or reusing chemicals within their manufacturing operations (EPA, 1995d).
As measured by reduced total emissions of toxic chemicals to the air, soil, and water,
pollution prevention programs have been successful (EPA, 1997c). However, a reduction in total
emissions reveals only part of the story. Reduced emissions do not necessarily equate to a
proportional reduction of health risks. The relative change in health risks may be
disproportionately larger or smaller than the reduction in total emissions because health risks are a
function of both the degree of exposure to toxic chemicals and the nature and intensity of the
chemicals' toxic effects. With regards to exposure, reducing emissions where there is little or no
exposure would yield a smaller health benefit relative to reducing emissions where there is much
potential exposure. With regards to toxicity, a large decrease in the emission of a chemical of
relatively low toxicity may have a smaller health benefit than a small decrease in a more toxic
compound. Only by describing emissions in terms of both exposure and toxicity can any health
benefits from reduced emissions be determined.
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Risk assessment is the process of estimating the chance that adverse health effects will result
from exposure to a chemical, biological, or physical agent. Human health risk assessment
attempts to quantify the adverse health effects by identifying the nature of the potential injury
(hazard identification) and the populations that are at risk (exposure assessment), by measuring
the relationship between a given exposure and the potential injury (dose-response assessment),
and by combining these three pieces of information to estimate the probability that harm will
occur (risk characterization) (NRC, 1983; NRC 1994). Risk assessment is used by EPA and
others as one input to making risk management decisions.
Risk management is the process of identifying, evaluating, selecting, and implementing
actions to reduce risk to human health and to ecosystems. The goal of risk management is to
identify and implement actions that reduce or prevent risks while taking into account social,
cultural, ethical, political, and legal considerations. A recent report by the
Presidential/Congressional Commission on Risk Assessment and Risk Management (1997a,
1997b) emphasizes the importance of engaging stakeholders throughout the risk assessment/risk
management process to assure that risk managers~e.g., government officials—take into account
these considerations to achieve good risk management decisions.
The development of a better understanding of the risks to workers and surrounding
communities associated with emissions from individual facilities is a high priority issue for
stakeholders in EPA's CSI Metal Finishing Sector (EPA, 1997a). Platers, environmental groups,.
community groups, labor, and regulators all need and want to know what emissions are being
produced and in what amounts by metal finishing operations. They also want to know what
health risks those emissions create for workers and the surrounding communities. The process of
risk assessment can provide a tool for stakeholders associated with the metal finishing industry to
better understand and evaluate the human health effects associated with chemicals emitted by
metal finishing facilities. The next two sections provide a brief overview of the metal finishing
industry and discuss the forum (i.e., the EPA's Common Sense Initiative) that provided the
impetus for this project.
1.2 THE METAL FINISHING INDUSTRY
The metal finishing industry encompasses a broad range of processes that are performed on
manufactured parts, usually after they have been shaped and machined (Murphy, 1996; EPA,
1995 a, 1995c). These processes generally alter the surface of the article to lend it properties not
possessed in its "unfinished state." The processes most commonly impart a decorative finish on
the article or provide it with additional functional characteristics such as corrosion resistance.
Common metal finishing operations include electroplating, electroless plating, anodizing,
conversion coating, and painting (Murphy, 1996). Additional steps that may be performed before
or after finishing operations include cleaning (e.g., degreasing with organic solvents), etching, and
corrosion protection. Many of these processes (e.g., electroplating, electroless plating, and
anodizing) involve the immersion of the metal parts through a series of liquid baths containing
solutions that impart the desired finish.
The metal finishing industry is comprised of both "job shops," mostly small businesses with
limited capital and personnel, and "captive" metal finishing operations within larger manufacturing
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facilities. Job shops perform finishing processes on parts that they receive from outside sources,
whereas captive shops perform finishing processes on parts that their firms manufacture. Captive
shops are typically involved in the manufacture of such items as machinery, automobiles,
appliances, and musical instruments. Job shops involved in metal finishing are classified primarily
under the Department of Commerce's Standard Industrial Classification (SIC) Code 3471, metal
plating and polishing. Manufacturing facilities that incorporate captive shops are generally
classified within SIC Codes 34 through 39, which encompass facilities that fabricate metal
products.
Estimates of the number of metal finishing facilities varies somewhat depending upon how
the industry is defined, but it is believed to include about 3,000 job shops and about 10,000
captive shops (EPA, 1997d). The typical job shop is about 30 years old, employs about 10 to 20
people and has annual net sales of approximately $1.1 million (NCMS, 1994; CAMP, 1995).
Facilities can be found throughout the country, but are concentrated in industrialized areas in the
Northeast, Midwest, Texas, and California.
Metal finishing facilities release a variety of toxic compounds (EPA, 1995a). Chlorinated
hydrocarbons are emitted during cleaning (degreasing) of metal parts, caustic mists, cyanides, and
metals are released from electroplating operations; and volatile organic compounds are emitted
during painting. The emitted chemicals can cause a variety of adverse health effects depending
upon the toxic nature of the chemical; the medium of exposure (i.e., air, water, soil, or food); the
chemical concentration to which an individual is exposed; and the duration and frequency of the
exposure. In addition, exposed individuals will have varying degrees of sensitivity to chemicals
depending upon the person's health status, age, and sex. Adverse health effects may include
cancer (hexavalent chromium, benzene), developmental toxicity (lead, mercury, glycols),
neurotoxicity (solvents, mercury), chemical bums (acids and alkalis), or dermal, respiratory, or
eye irritation (acid vapors, solvents, metals) (Klaasen, 1995).
Table 1-1 lists some of the chemicals that may be found in metal finishing process emissions
(EPA, 1995a). The list is not a description of the actual emissions from any specific facility.
Emissions from each facility are dependent upon the processes performed and the types and
effectiveness of any pollution control practices and control devices that are used at the facility. By
combining emissions data with chemical exposure and toxicity information in the risk assessment
process, an evaluation of the human health effects of emissions can be made.
1.3 COMMON SENSE INITIATIVE
CSI is an attempt by EPA to take a new approach to creating policies and environmental
management solutions for American industries (Browner, 1994). Participants in the CSI program
have been asked to work together to achieve environmental protection on an industry-by-industry
basis. Stakeholders associated with six industrial sectors—automobile manufacturing, computers
and electronics, iron and steel, printing, metal finishing, and petroleum refining—currently
participate in the CSI program. These six sectors represent a cross-section of American industry
and taken together they comprise over 11% of the U.S. Gross National Product; employ over 4
million people; and account for about 12% of reported releases of toxic substances. Because of
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Table 1-1
Chemical Substances Potentially Used in, Generated by, or Emitted
from Metal Finishing Facilities
Metals and Metal Compounds
Aluminum
Arsenic, arsenic disulfide
Barium
Cadmium, cadmium acetate, cadmium chloride
Chromium, chromic acid
Copper
Iron
Lead
Manganese
Mercury
Nickel, nickel acetate, nickel sulfate
Nickel-cobalt acetate
Selenium
Silver
Tin-lead
Zinc
Alkalis
Sodium hydroxide
Cyanides
Potassium cyanide
Sodium cyanide
Zinc cyanide
Strong Acids
Hydrochloric acid
Hydrofluoric acid
Nitric acid
Phosphoric acid
Sulfuric acid
Weak Acids
Acetic acid
Citric acid
Oxalic acid
Tartaric acid
Other Inorganics
Chlorine
Fluoride
Potassium nitrate
Sulfur dioxide
Organics
Acetone
Acetone cyanohydrin
Benzene
Carbon disulfide
Carbon tetrachloride
Chlorinated fluorocarbons, l,l,2-trichloro-l,2,2-
trifluoroethane (Freon-113), Trichlorofluoro-
methane
Chlorobenzene
Chloroform
Cresols (cresylic acid)
Dichloromethane (methylene chloride)
Ethyl acetate
Ethyl benzene
Ethyl ether
2-ethoxyethanol
Formaldehyde
Glycols
Isobutanol
Kerosene
Ketones, cyclohexanone, methyl ethyl ketone, methyl
isobutyl ketone
Methanol
Mineral oil
Naphtha
n-butyl alcohol
Nitrobenzene
2-nitropropane
1,2-dichlorobenzene
Phenol
Pyridme
Tetrachloroethylene
Toluene
1,2,4-trichlorobenzene
1,1,1 -trichloroethane
1,1,2-trichloroethane
Trichloroethylene
Xylene
(Modified from USEPA, 1995c)
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the importance of these industries as measured by these characteristics and because of their
diversity in size, products, and operations, EPA believes that they offer an excellent opportunity
to create environmental solutions that can operate across industries and to expand CSI to other
sectors (EPA, 1994).
The overall direction of CSI is determined by stakeholders from each industry sector. A
CSI Council, comprised of high-level decision-makers from all stakeholder groups and across all
involved industrial sectors, provides a forum for the exchange of ideas among sectors (Figure 1-
1). The CSI Council is chaired by the EPA Administrator. For each industrial sector in CSI, EPA
also has convened a team of stakeholders (i.e., a sector-specific subcommittee) that looks for
opportunities to create new sector-specific alternatives to the current regulatory system to achieve
greater environmental gains at less cost to industries and taxpayers (a process sometimes labeled
"cleaner, cheaper, smarter") (EPA, 1994).
Figure 1-1
Metal Finishing Sector Organization
Within the Common Sense Initiative
Common Sense
Initiative Council
Printing
Subcommittee
Petroleum
Refining
Subcommittee
Metal
Finishing
Subcommittee
Metal Finishing
Sector
Work Groups
±
Iron and Steel
Subcommittee
Computers &
Electronics
Subcommittee
JL
Auto
Manufacturing
Subcommittee
Regulatory and Reporting
Research and Technology
Risk Characterization
Promoting Improved Performance
Environmentally Responsible Transition
Compliance and Enforcement
Access to Capital
Strategic Goals
EPA hopes that CSI, with its involvement of a diverse and comprehensive group of
stakeholders, will serve as a model for changing the environmental protection process from one of
conflict to one of collaboration and consensus. Historically, much of EPA's rule-making has
resulted in litigation. This process diverts valuable resources of all parties from the work of
protecting the environment and public health. The EPA hopes CSI will provide a forum within
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which former adversaries will become partners in protecting the environment. To assure
communication among stakeholders, sector subcommittees have met regularly since CSFs
inception to identify and refine their objectives, to plan projects to meet those objectives, and to
discuss progress in the various projects underway, policy considerations, and other issues (EPA,
1997d).
Each industry sector subcommittee has been asked to explore common issues, including
alternative regulatory systems, pollution prevention, reporting, compliance, permitting, and
environmental technology, that may have broad applicability to their sector as well as to other
industry sectors. EPA hopes that the new systems will be more flexible, will encourage
innovation, and will be tailored to the needs of the industry and its environmental problems, while
at the same time the systems will encourage public participation, provide information about
facilities' environmental performance, and meet or exceed legal requirements (EPA, 1994).
The Metal Finishing Subcommittee has about 24 members representing metal finishing
companies, trade associations, suppliers, environmental and community groups, organized labor
and state and local governments. Representative organizations include the American
Electroplaters and Surface Finishers Society (AESF), the Natural Resources Defense Council
(NRDC), the United Auto Workers (UAW), the Barrio Planners of Los Angeles, the Water
Environment Federation, and the Association of Municipal Sewerage Agencies (AMSA).
Members of the subcommittee have identified a set of National Performance Goals for the sector
that include three facility-based performance goals:
• Reduction in hazardous emissions and exposures ("cleaner");
• Increased economic payback and decreased costs ("cheaper");
• Improved resource utilization ("smarter");
and two sector-wide performance goals:
• Industry-wide achievement of the facility-based goals;
• Industry-wide compliance with environmental performance requirements (EPA,
1997b).
To meet these goals, the subcommittee has endorsed 14 projects, and supports an additional CSI
small business sector project. It has created eight work groups (Figure 1-1) to carry out these
projects and to identify important needs for the sector.
The Metal Finishing Subcommittee's Research and Technology Work Group examines and
provides information about new technologies for the metal finishing industry and seeks to better
understand the technology needs of the metal finishing industry, as a basis for tailoring Federal
and private sector research and development to meet those needs. The work group's desired end
product is a "customer-oriented" research and development strategy for the industry. The work
group's objectives are to assure that research efforts (including technology transfer and diffusion)
will address the most significant environmental needs of the metal finishing industry; that the
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results will be accessible to the typical metal finishing job shop; and that the research program will
focus on pollution prevention and remediation technologies, so as to be of greatest benefit to
small job shops, some of which are located in brownfield areas.
The work described herein was undertaken in response to one of eight priority research
needs identified by the Research and Technology Work Group in its National Metal Finishing
Environmental R&D Plan (R&D Plan) (EPA, 1997a). The eight priority research needs were
identified from among 74 projects that were rated by 27 experts from all metal finishing sector
stakeholder groups. The experts rated the research needs according to three criteria—the likely
impact of the project in achieving or exceeding Federal, state, and local compliance requirements;
achieving widespread adoption within the industry; and reducing risks to workers, the
surrounding community, and the environment. The rating system was used to prioritize research
and development needs and to make recommendations for the highest priority research areas.
The eight specific recommendations for further research that were made in the R&D Plan
include:
• Develop and apply simple methods to describe the emissions from plating operations
and use these values to characterize risks to workers, surrounding communities, and
the environment;
• Continue and expand research and development on various aspects of reducing and
eliminating multi-media emissions from hexavalent chromium plating operations;
• Focus research and development on reducing cyanide emissions and on developing
improved analytic methods to determine the presence, concentration, and impacts of
cyanide in waste streams;
• Demonstrate methods of off-site recovery of metals, acids, and cleaners;
• Focus research and development on low emission and emissionless chlorinated solvent
vapor degreasing systems for metal plating operations and on evaluating alternatives to
chlorinated solvents for cleaning—especially new, alternative cleaners that have
recently come on the market;
• Develop a rapid verification protocol that provides information on technology
performance, cost and maintenance requirements on which companies could base
decisions to purchase technologies;
• Conduct research and development to reduce cadmium emissions and to seek
alternatives to its use; and
• Develop and disseminate short, well-researched, peer-reviewed articles on the
selection and use of simple technologies for improved environmental performance.
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1.4 PROJECT OBJECTIVES
Among the goals in the R&D Plan the highest priority was given to developing and
applying simple methods to characterize the emissions from plating operations (and more
specifically, chromium electroplating operations) and to use the output from these methods to
characterize the health risks to workers, surrounding communities, and the environment (EPA,
1997a). To help attain this goal the objectives of this project are:
1) to identify the types and sources of information that are needed to assess risks to
workers and surrounding communities from metal finishing facilities;
2) to develop a general facility model that describes potential human exposure
pathways;
3) to present equations that characterize the exposure pathways from emission
sources to workers and the public; and
4) to quantify the lifetime excess cancer risk and potential for other health hazards
from hexavalent chromium in a screening risk assessment process.
By explaining the steps performed and the data needed to conduct a risk assessment we hope to
assist those associated with the industry to better understand the risk assessment process and the
questions that can be answered by the process.
Although this report focuses on the potential effects that emissions from metal finishing
operations may have on human health, emissions from some facilities may also affect ecological
receptors. An ecological risk assessment can be performed for those facilities where ecological
receptors may be at risk beginning with a problem formulation phase that develops a site
conceptual model for the ecological receptors at risk and identifies the questions that the risk
assessment process would be designed to answer (EPA, 1996b).
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2. RISK ASSESSMENT FOR METAL FINISHING FACILITIES
2.1 THE RISK ASSESSMENT PROCESS
Human health risk assessment is one part of the process that begins with the recognition
that a potential health problem exists (Problem Formulation) and continues to a decision by risk
managers to take actions (Risk Management) to reduce or eliminate any identified potential for
harm (Figure 2-1). Risk assessment entails the evaluation of information on the hazardous
properties of chemicals and the extent of human exposure and the characterization of the resulting
risks. The complete risk assessment process is comprised of four steps—hazard identification,
dose-response assessment, exposure assessment, and risk characterization (NRC, 1983; 1994).
Figure 2-1
The Risk Assessment/Risk Management Paradigm
Research _
Epidemiology
Clinical Studies
Animal Studies
Cell/Tissue Experiments
Exposure Monitoring
Develop Fate and
Transport Models
rroDiem rormuiation -*-
Discussion Among Risk Assessor,
Risk Manager, and Stakeholders
-^P-
_. . .
Risk Assessment ~^~
^^,
" Hazard Identification
Dose Response Assessment
Exposure Assessment
Risk Characterization
-^P^
Risk Communication
Discussion Among Risk Assessor,
Risk Manager, and Stakeholders
~^0-
Risk Management
Evaluation of Public Health, Social,
Economic, Political, Engineering
Factors
Repeat St<
•o
W
fi>
V>
3
CO
(D
D.
O
a
1
Decision or Action
No Action
Information Programs
Economic Incentives
Ambient Standards
Pollution Prevention
Chemical Substitution
Chemical Ban
(Based on NRC, 1983; 1994)
Although complete risk assessments contain all four steps, they may nevertheless involve
varying levels of effort. Risk assessments are often performed using a phased approach hi which
upper estimates of exposure and chemical concentrations, which are believed to be conservative
(i.e., health protective) and likely to overestimate risk, are first used to assess risk. A phased
approach to risk assessment allows the risk assessor to identify those health risks that are
potentially the most important and consequently to eliminate from further evaluation those
chemical exposures that clearly do not present a health risk. This approach simplifies and focuses
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subsequent phases of analysis and at the same time reduces the cost and time to perform the risk
assessment, especially at facilities with relatively low levels of emissions or emissions of relatively
non-toxic compounds.
Problem formulation is a useful process to perform prior to the risk assessment process
because it provides an opportunity to gather input from all stakeholders prior to commencing any
analysis. The purpose of the problem formulation process is to sharpen the focus of the risk
assessment on those problems of greatest concern to those persons, risk managers and
stakeholders alike, who will be using the information. Problem formulation may involve a
statement of the suspected problem based on available information; the identification of questions
to be answered by the risk assessment; the identification of any research that may be needed
before beginning the risk assessment; and/or the presentation, review, and comment on an analysis
plan for the risk assessment process. Once the objectives of the risk assessment process have
been identified the four steps of risk assessment can be conducted.
The first step of the risk assessment process, hazard identification, seeks to identify the
potential health effects (e.g., dermal irritation, neurotoxicity, cancer, reproductive toxicant) that
may result from exposure to a chemical or physical agent. This information is gathered from the
health effects literature, which may provide evidence either for or against the agent as the cause of
a specific type of health effect. Such studies often characterize the behavior of a chemical within
the body and its interactions with organs, cells, or even parts of cells. Data regarding these
interactions may be of value in answering the ultimate question of whether the forms of toxicity
observed in an epidemiology study, population group, or test animal are also likely to occur as a
result of an environmental exposure.
For any harmful effect that is identified, the second step of the risk assessment process,
dose-response assessment, is conducted. Dose-response assessment attempts to determine the
relationship between the quantity of substance to which an individual is exposed and the severity
of the adverse health effect. Dose-response data are derived from animal studies or, less
frequently, from studies in exposed human populations (e.g., epidemiological studies of workers
have been performed for chemicals of concern to industry). There may be several dose-response
relationships for a substance because it may induce more than one type of harmful effect or it may
induce different effects via different pathways of exposure. The level of confidence in an estimate
of a dose-response relationship is partly dependent upon the source of data used to derive the
estimate. Generally, estimates derived from human studies, such as epidemiological studies of
workers, contain less uncertainty than those derived from animal studies. The first two steps of
the risk assessment process are chemical (substance) specific. Once completed, the information
can be used again in many assessments of various "real-life" situations.
The third step of the risk assessment process, exposure assessment, seeks to characterize
"real-life" situations by determining the intensity, frequency, and duration of exposures to the
chemical substance(s) in question that are known to occur or could occur in the future. Exposure
assessments can evaluate past, present, or future exposures and may involve either direct or
indirect assessments of exposure. Direct assessments measure the contact between the exposed
person(s) and the substance(s) being studied through the use of personal monitors (e.g., a small
air pump and filter that collects air contaminants from within the breathing zone of the person
10
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being studied). Indirect assessment uses measurements of concentrations and other data in the
physical surroundings of the people being studied (e.g., air flow direction and rate), along with
information about where the people are and what they are doing to bring themselves into contact
with the substance(s).
Risk characterization, the final step of the risk assessment process, combines the
assessments of hazard, dose-response, and exposure to estimate the probability of the occurrence
of a specific adverse effect in an exposed individual or population. The results of the risk
characterization are then communicated to risk managers and other interested parties with an
overall analysis of the quality of the information in the assessment (NRC, 1994). The uncertainty
associated with the risk assessment and the sources of this uncertainty are presented. The
uncertainty analysis should indicate whether the assumptions made in the preceding steps tend to
under- or over-estimate the level of risk.
Risk assessment is closely linked but distinct from risk management, the process by which
the results of a risk assessment are integrated with political, social, economic, and engineering
considerations to arrive at decisions about the need and methods for reducing risk. A risk
assessment should be prepared, therefore, with both risk managers and stakeholders in mind, to
assure that appropriate information will be provided in a format that is understandable and useable
to all interested parties. Maintaining communication among risk managers, stakeholders, and the
risk assessor throughout the risk assessment process will increase the likelihood that all interested
parties will remain engaged in the process and will contribute input on political, social, and
economic issues that are part of the risk management process.
2.1.1 Hazard Identification
The first step of the risk assessment process at a metal finishing facility is to identify the
chemicals present that may affect human health (Table 2-1). Chemicals that may be used, stored,
or generated at the facility from all potential sources including raw materials, process
intermediates, and waste products should be considered. A preliminary list of the hazardous
substances that may be associated with metal finishing processes has been compiled (Table 1-1)
(EPA, 1995a). The actual list of chemicals at any given facility will consist of a subset of this list,
possibly supplemented with additional chemicals (e.g., as technology innovations occur and new
chemical processes are developed, additional chemicals may require evaluation). Raw materials
could be identified from company purchasing records or from the facility's Material Safety Data
Sheets; process intermediates could be identified by evaluating the chemical processes that are
conducted at the facility; and waste products could be identified from government-required
reporting forms such as EPA forms for the reporting of chemicals to the Toxic Release Inventory.
Once a facility-specific list of chemicals is compiled, the adverse health effects associated
with the chemicals can be identified by reviewing existing toxicological information. One source
of this information is EPA's Integrated Risk Information System (IRIS), which is available on the
internet (www.epa.gov/ncea/iris.htm). It is possible at this step of the risk assessment that some
chemicals will be identified for which little or no toxicological information is available. Lack of
such information is a source of uncertainty in the risk assessment. Additional laboratory or
epidemiological research on the chemicals may be needed to reduce this uncertainty.
11
-------
Table 2-1
Principle Steps of the Risk Assessment Process
for Metal Finishing Facilities
Risk Assessment Step
Associated Tasks
Hazard Identification
Identify chemicals emitted or released from known chemical usage and
emissions data from the facility or industrial sector.
Identify unwanted health effects of chemicals that are emitted or released.
Dose-Response Assessment
Identify cancer potency factors, unit risks, reference concentrations, and
reference doses for each chemical as derived by EPA or by others from
animal studies and human epidemiological studies.
Verify assumptions used in existing data with historical information about
the facility or industrial sector.
Exposure Assessment
Collect plant emissions information from permits, emissions reports,
interviews, and industry records. Characterize any variations in
emissions over time (e.g., daily or longer term fluctuations that result
from variations in facility schedules and production runs).
For workers, describe work environment, such as ventilation in rooms, air
exchange rates, direction of air flow, and whether any special systems are
present to prevent or reduce worker exposure (including any personal
protective equipment that workers may be required to wear). Describe
design, placement and effectiveness of building ventilation system.
For more refined assessments of exposure pathways in air, obtain
meteorological data from weather service and air districts (commonly
available for use in EPA air models) and predict concentrations of
pollutants in air at varying distances from the emission source using air
dispersion model(s).
For more refined assessments of exposure pathways in water, collect
hydrogeological data from United States Geological Survey (USGS),
water districts, or state and county governments and use to predict the
movement of chemicals in groundwater and surface water.
Collect demographic information from census information, county and
city records, and site surveillance.
Verify concentrations of chemicals in environmental media through
workplace and/or community observation and/or monitoring. Describe
how emissions controls and environmental fate and transport processes
affect exposure concentrations for off-site populations.
Risk Characterization
Describe the probability of unwanted health effects by combining
information from hazard identification, dose-response assessment, and
exposure assessment steps.
Identify and discuss sources of uncertainty and variability associated with
variables in the risk assessment.
(Based on Schaum, 1997)
12
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2.1.2 Dose-Response Assessment
The dose-response assessment attempts to determine the relationship between the quantity
of substance ingested, inhaled, and/or absorbed (e.g., through the skin) and the probability of the
occurrence and severity of an adverse health effect. The dose-response assessment considers
whether sensitive or special populations, such as children, persons with compromised immune
systems, or the elderly may be more susceptible to a chemical's harmful effects. Generally, dose-
response information is gathered from two types of sources—animal studies and human
epidemiologjcal studies. Dose-response values derived from both types of studies contain some
degree of uncertainty. Values that are based on animal studies are extrapolated from the
responses of test animals that are exposed under laboratory conditions, often at relatively high
concentrations. Adjustments must be made to the experimentally-derived dose-response values to
obtain a dose-response value appropriate for humans. The adjustments account for metabolic and
physiological differences between humans and animals, differences in exposure duration and
intensity, and differences in exposure pathways (e.g., ingestion in food versus ingestion in water).
Values that are based on studies of human populations contain less uncertainty but still often
require extrapolation from a high dose, short-term exposure, such as occurs from accidental
exposure or an intentional overdose, to a low dose, chronic exposure. When the studied
population used to derive the dose-response value is similar to the population of interest in the
risk assessment (e.g., epidemiological studies of workers used to derive safe workplace
concentrations) the estimates of dose-response are more certain.
EPA's IRIS database contains dose-response information for over 500 specific chemical
substances. The database was initially developed for EPA staff in response to demand for
consistent information on chemical substances for use in risk assessments, decision-making, and
regulatory activities. Dose-response values in the database represent EPA consensus scientific
positions on potential adverse human health effects that may result from chronic (e.g., lifetime)
exposure to environmental contaminants. This information has been evaluated by scientists from
EPA's program offices and Office of Research and Development (ORD) who are experienced in
issues related to both the qualitative and quantitative risk assessment of carcinogenic and toxic
agents. The review process leads to an internal EPA scientific consensus regarding risk
assessment information on a chemical.
Dose-Response Values for Noncarcinogenic Effects. One widely held view among
toxicologists is that many of the harmful effects that result from exposure to toxic chemicals occur
only when an individual's exposure (via inhalation, ingestion, and/or dermal contact) exceeds
some threshold level of uptake. The threshold level is generally expressed as a chemical dose
(e.g., reference dose, or RfD) to which an individual may be exposed over a portion of a lifetime
(subchronic RfD) or during a lifetime (chronic RfD) without an appreciable risk of adverse
effects. The chemical dose is expressed as the weight of chemical per kilogram of body weight
per day (e.g., milligrams/kilogram»day or mg/kg*day). For chemicals in air the threshold level is
expressed as a concentration (reference concentration, or RfC) such as micrograms of chemical
per cubic meter of air (ug/nr*).
The dose-response values noncarcinogenic effects are based on toxicological information
derived from either animal or human studies. Chemical exposure in these studies may be acute (a
brief exposure of a few minutes to a few days), subchronic (a few weeks to months), or chronic
13
-------
(usually includes at least a tenth of the life span of a species, generally six months or more).
Chronic exposures generally have the lowest thresholds for adverse effects and are most
commonly used to derive chemical RfDs and RfCs for EPA risk assessments. However, if
emissions are episodic or of short duration, the RfDs and RfCs that relate to acute exposures may
be appropriate to use in the risk assessment. The RfDs and RfCs cited in this report were derived
by EPA's program offices and ORD and have been reported in the IRIS database or in EPA's
Health Effects Assessment Summary Tables (EPA 1995b; 1997e) (Table 2-2). These values are
estimates (with uncertainty spanning perhaps an order of magnitude) of continuous exposure to
the human population that are likely to be without appreciable risk of deleterious effects during a
lifetime.
EPA's RfDs and RfCs have been calculated to be protective of sensitive members of human
populations. A margin of safety has been applied to derive RfDs and RfCs from experimental
data. This margin of safety is applied to account for intra- and inter-species variations, for limited
or incomplete data, for evaluating the significance of adverse effects, and for adequately
protecting sensitive human populations. In practice, the experimentally-derived values are divided
by an uncertainty factor (generally, a number between 3 and 1,000) and possibly by an additional
modifying factor to add this margin of safety to the RfDs and RfCs. EPA's rationale for the
application of these safety factors is given in the IRIS database for each chemical where a RfD or
RfC is given.
Dose-Response Values for Carcinogenic Effects. EPA considers the weight of evidence
that a chemical is a carcinogen and for chemicals that are known or likely to cause cancer, the
agency calculates an oral slope factor and/or inhalation unit risk (EPA, 1986; 1996a). Oral slope
factors and unit risks are estimates of the relationship between dose or concentration and the
probability that a chemical will induce cancer. Oral slope factors are upper bound estimates of the
cancer risk per unit intake of a chemical over a person's lifetime. Inhalation unit risks are upper
bound estimates of the cancer risk per unit of concentration of a chemical in air over a person's
lifetime. Because the slope factors and unit risks are upper bound estimates, the risk of cancer for
an exposed individual over a lifetime is unlikely to exceed the calculated probability and likely will
be less. Oral slope factors and/or inhalation unit risks are given in Table 2-2 for each chemical
where information is available. Slope factors are expressed as the inverse of the dose,
"(rng/kg*day)"V while unit risks are expressed as the inverse of concentration, "(ng/m3)"1"
Slope factors and unit risks in this report were derived by EPA's program offices and ORD.
Some states, notably California, have derived slope factors that differ from those derived by EPA
(DTSC, 1994b).
The dose-response estimates have numerous uncertainties, including those associated with
extrapolations from animal data to humans and from high experimental doses to lower
environmental exposures. These uncertainties may span an order of magnitude or more. Actual
incidence of health effects is influenced by the physiology and health-status of the exposed
individual or populations such as general health, age, and sex and by the degree of exposure to the
chemical, which is estimated during the exposure assessment step of the risk assessment (EPA,
1993).
14
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Table 2-2
Published EPA Human Health Toxicity Values for Chemical Substances
Potentially Emitted by Metal Finishing Processes
Chemical
Metals (1)
Aluminum
Arsenic
Barium
Cadmium
Chromium (VI)
Copper
Iron
Lead
Manganese
Mercury (3)
Nickel
Selenium
RfC
mg/m3
|'ft|f"i
ill::. "'JV^-lv: .;;.
5.0 x 10'4
n.d.
n.d
n,d.
n,d.
Bas
5.0 x 10'5
3.0 x lO'4
n.d.
n.d
unit risk
(lig/mV
m.*m
4.3 x 10"3
'•••'•'•'.-n-iai^-.
1.8 x 10'3
1.2 x 1C'2
•::,.n.a,;,;'
' ':[''.'M'. :':/ '
^d on biokine
n.a.
n.a.
n.a.
n.a.
RfD0
mg/kg/day
1.0 xlO1
3.0x10-"
7.0 x 10'2
5.0 x 10'4
5.0 x 10-3
3.7xlO'2
n.d.
SF0
(mg/kg/day)-1
.::/'• n^a- '!
1.5 x 10°
:::v'::nift;:-' !;j;:
;;:::::.n;a.' /.:!!;
::: n.a. !.'
.:; :-.*><8:. :;.. •'
':•;•• •ihia.^;i::::
tic uptake models
4.7 x ID'2
3.0 x 10'4
2.0 x 10'2
5.0 x ID'3
';: ;;•' n;a.': ' :.:.
::::;:::,n.a.:. •:;;:;.
:;; /.:bia.;:;:;:;;;
:':;::n:a.: '-:'
Chemical
Silver
Tin
Zinc
Alkalis (4)
Sodium hydroxide
Cyanides
Potassium cyanide
Sodium cyanide
Zinc cyanide
Mineral Acids (4)
Hydrochloric acid
Hydrofluoric, nitric, and
sulfuric acids
Phosphoric acid
RfC
mg/m3
n.d.
ltd.
n.d.
'I.1 . ^.li: . .::
n.d.
n.d.
n.d.
2.0 x 1Q-2
n.cL
l.Ox 10'2
unit risk
(ng'm3)'1
n.a.
n.a.
n.a.
ii::;:: 'n.a. ... . .;
n
-------
Table 2-2 (continued)
Published EPA Human Health Toxicity Values for Chemical Substances
Potentially Emitted by Metal Finishing Processes
Chemical
Organic Acids (4)
Acetic, citric, oxalic, and
tartaric acids
Other Inorganics
Fluoride
Potassium nitrate (5)
Sulfur dioxide
Chlorine
Organics
Acetone
Acetone cyanohydrin
Benzene
Carbon disulfide
Carbon tetrachloride
RfC
mg/m3
n.d.
n.d.
n.d.
n.d,
n.d.
: .»•<>•
n,d.
6.0 x 10'3
7.0x10-'
2.0 x 10'3
unit risk
(jig/m3)-1
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
: n.a.
8.3 x 10'6
n.a.
l.SxlO'5
RfD0
mg/kg/day
n.d.
6.0 x 10'2
1.6x10°
n.a.
1.0 x 10°
1.0 xlO'1
8.0 x 10'4
n.d. ....,
1.0 x 10'1
7.0 x 10-"
SF0
(mg/kg/day)'1
n.a.
n,a.
n,a.
n,a.
n.a.
n,a.
n.a.
2.9 x 1Q-2
nia.
1.3 x 10-'
Chemical
Chlorobenzene
Chloroform
Cresol (Cresylic acid)
Cyclohexanone
1 ,2-dichlorobenzene
Dichloromethane
(methylene chloride)
2-ethoxyethanol
Ethyl acetate
Ethylbenzene
Ethyl ether
Formaldehyde
Glycols (6)
Isobutanol
RfC
mg/m3
2.0 x 10'2
n.d
n d
n.d.
2.0 x ID'1
3.0x10°
2.0 x 10''
n.d.
1.0x10°
n.d.
'••• "4
n.d.
n.d.
unit risk
(ng'm3)'1
n.a.
2.3 x 10'5
n.a.
n,a.
n,a.
4.7 x 1Q-7
n.a.
n.a.
; n,a.
n.a.
1.3 x ID'5
n,a.
: n.a.
RfD0
mg/kg/day
2.0 x lO'2
1.0 x 10'2
n.d.
5.0 x 10°
9.0 x 10'2
6.0 x 10'2
4.0 x 10'1
9.0 x 10'1
1.0 x 10'1
2.0 x 10'1
2.0 x 10"'
2.0x10°
3.0x10-'
SF0
(mg/kg/day)"1
n.a.
6.1 x 10'3
n.a.
n,a.
n,a.
7.5 x 1Q-3
n,a.
n.a.
n,a.
n,a.
n,d,
n.a.
n,a.
Footnotes are listed at end of Table 2-2.
16
-------
Table 2-2 (continued)
Published EPA Human Health Toxicity Values for Chemical Substances
Potentially Emitted by Metal Finishing Processes
Chemical
Kerosene
Methanol
Methyl ethyl ketone
Methyl isobutyl ketone
Mineral oil
Naphtha
n-butyl alcohol
Nitrobenzene
2-nitropropane
Phenol
RfC
mg/m3
n.d
n.d.
1.0x10°
8.0 x 10'2
n,d,
fl.d
n.d.
2.0 x 10'3
2.0 x 10'2
n.d.
unit risk
(ng/m3)-'
n.a.
n.a.
n.a;
n.a.
n.a.
n,a.
n.a.
n.a.
n.a.
n.a.
RfD0
mg/kg/day
n.d.
5.0 x ID'1
6.0 x 10'1
8.0 x ID'2
n.d.
ti.d.
l.OxlO'1
5.0 x lO'4
n.d.
6.0 x 10'1
SF0
(mg/kg/day)-1
n.a.
n.a.
n,a.
n,a.
n,a.
ita.
n.a.
n.a.
n.a.
n.a.
Chemical
Pyridine
Tetrachloroethylene
(perchloroethylene)
Toluene
1 ,2,4-trichlorobenzene
Trichlorofluoromethane
(Freon-11)
1,1,2-trichloro- 1,2,2-
trifluoroethane (Freon-113)
1,1,1 -trichloroethane
1 , 1 ,2-trichloroethane
Trichloroethylene
Xylene (1)
RfC
mg/m"
rV:M^':'.'f
:' ::;; ltd/":. ::
4.0 x 10'1
2.0 x ID'1
7.0 x 10-'
3.0x10'
ltd.
n.d
rtd.
ruL
unit risk
(ng/m3)'1
:..::::' n.a:..
^•:;'n.dr
• ;:: n,a. • .
n:y'.h;a.:::l:'
i::l n4
; n.a.
n.a.
1.6 x 10'5
n.d.
n.a.
RfD0
mg/kg/day
1.0 x 10-3
1.0 x 10'2
2.0 x 10'1
l.OxlO-2
3.0 x 10"'
3.0 x 101
3.5xlO'2
4.0 x 10'3
6.0 x 10'3
2.0 x 10°
SF0
(mg/kg/day)-1
n.a.
5.2 x 10-2
n,a.
n,a.
n,a.
n.a.
n.a.
5.7 x 10"2
l.lxlO'2
n.a.
Source: (EPA 1995b; 1997e) Because the source references are updated periodically, values in table should be verified before using in a risk assessment.
(1) Includes metals and metal compounds
(2) n.d. - not determined. EPA has not determined a reference concentration, reference dose, or unit risk for this chemical.
n.a. - not applicable. Cancer slope factor or unit risk value has not been derived for this chemical because there is a lack of evidence that indicates that this
chemical is a carcinogen, because this chemical is not carcinogenic, or because the chemical is not carcinogenic by the oral or inhalation exposure route.
(3) RfD0 is for mercuric chloride; RfC is for elemental mercury.
(4) The primary hazard associated with most acids and alkalis is corrosivity. The more volatile acids produce irritating vapors.
(5) Values for potassium nitrate are based on the toxicity of the nitrate anion and are expressed as nitrate-nitrogen.
(6) Values in table are for ethylene glycol; values for other glycols will vary.
(7) Value is for mixed xylenes.
-------
2.1.3 Exposure Assessment
Exposure assessment seeks to determine the intensity, frequency, and duration of actual or
potential exposures to a chemical in the environment (Figure 2-2). To assess exposure,
information about the concentrations of chemicals in air, soil, water, and food is needed along
with information about how humans may be exposed to these media (through breathing, skin
contact with water or soil, drinking of water or milk, or eating produce or other foods) to assess
the level of exposure (Table 2-3). An individual's exposure will vary over time because chemical
concentrations in the environment vary (e.g., with distance from the emissions source or with time
as the chemical is dispersed by physical processes or is degraded by biological, chemical or
physical processes) and because an individual's location relative to the facility varies over time.
To accurately describe exposure for different groups of people, chemical concentrations in water,
air, soil, and food must be measured or estimated in several directions and at various distances
from a source of chemical emissions. Information about the variation in concentrations over time
also increases the accuracy of the exposure assessment. This information may be obtained by
measuring and analyzing emissions or, for outdoor air concentrations, by using environmental fate
and transport models and/or air dispersion models (e.g., ISC2, an existing EPA model, or the
Total Risk Integrated Methodology, which is currently in development) to establish the
relationship between emissions and chemical concentrations in the environment.
Figure 2-2
Conceptual Exposure Model for Electroplating Process
t
/Venti
y'Treatmer
>
i
ation N.
t System\^
..'-.'• ' • -. • - Fugi
• - I; ; ' Mist ' ; !• Emis!
• '• • formation- • '.
±
Plating Bath
i
Worker
Exposure
Inhalation
tive ' Ingestion
>ions jf _
/* Dermal
Jpills Contact
Water Treatment
System
f
\ /
,
\
(
^
(
i
i
\
^ i
I
•3
D
3
a
y
= Public
Exposure i
Inhak
^- Soil r—^-
, W"9
Water ^ ^
r
ition
-^.
estion
*•*•
nal
tact
Concentration data for each medium are combined with information regarding population
characteristics (e.g., volume of air breathed during different work activities, surface area of skin
exposed to soil during gardening, volume of water drunk, or amount of food consumed) and
18
-------
Table 2-3
Exposure Assessment Data Needs for Metal Finishing Facilities
Exposed
Population
Required Inputs
Chemical Concentration
Exposure Duration and
Frequency
Population
Characteristics
Nearby
Residents
Site-specific and media-specific
chemical concentration data
(concentrations may be
measured or modeled)
Regional or local area chemical
concentrations monitoring data
Emissions rate information
Local meteorology (wind
direction, speed, turbulence,
solar radiation)
Surrounding terrain and
buildings
Duration of residence
Daily activity patterns by age group:
Hours spent at home
Hours spent outdoors
Age
Sex
Health Status
Workers
Site-specific and media-specific
chemical concentration data
(concentrations may be
measured or modeled)
Materials balance for facility
processes
Ventilation patterns and
exchange rates
Controls on indoor emissions
Activity patterns by job description
or category
By job description or category:
Hours worked per week
Weeks worked per year
Years worked per job
Degree of exertion
Engineering and administrative
controls on exposure
Personnel protective equipment
Age
Sex
Health Status
(Based on Sdiaum, 1997)
activity patterns (e.g., hours spent performing a specific work process, hours spent at home
outdoors, number of years spent at a residential location) to determine the amount of chemical to
which an individual is exposed (Table 2-4).
In Table 2-4, all values (exclusive of conversion factors) that are used to calculate the
average daily dose have some degree of variability associated with them. Variability refers to
observed differences attributable to heterogeneity in a population or exposure parameter. Sources
of variability are the result of natural random processes and may be associated with
19
-------
Table 2-4
Generalized Dose Equations
Route of Exposure
Equation 2-1
Inhalation of Volatiles or Particulates
*nn _ r ,. InhRa x ETa x EFa x EDa
BW x AT x 365 days/yr
Equation 2-2
Ingestion of Soil, Dust, or Surface Deposits
Ann r ._ IRsxEFsxEDsXlCT6
AJJJJsi Us X
BW x AT x 365 days/yr
Equation 2-3
Ingestion of Water
APPuoL., = rwx IRwxEFwxEDw
BWxATx365days/yr
Values
ADDai
MlRa
ETa
EFa
EDa
BW
AT
ADD*
{-*$
IRs
EFS
EDS
10"6
BW
AT
ADD™
Cw =
IRw
EFW
EDW
BW
AT
= Average Daily Dose
via air inhalation
= Chemical concentration in air
(milligrams/meters3)
= Inhalation rate
(meters3/hour)
= Exposure time
(hours/day)
— Exposure frequency
(days/year)
= Exposure duration
(years)
= Body weight
(kilograms)
= Averaging time
(years)
= Average Daily Dose
via soil ingestion
= Chemical concentration in soil
(milligrams/ldlogram)
= Intake rate
(milligrams/day)
= Exposure frequency
(days/year)
- Exposure duration
(years)
= Conversion factor
(kilograms/milligram)
= Body weight
(kilograms)
= Averaging time
(years)
= Average Daily Dose
via water ingestion
Chemical concentration in water
(milligrams/liter)
= Intake rate
(liters/day)
= Exposure frequency
(days/year)
(years)
= Body weight
(kilograms)
= Averaging time
(years)
20
-------
Table 2-4 (continued)
Generalized Dose Equations
Equation 2-4
Dermal Contact with Soil, Dust or Surface Deposits
= c x SSAs x AF x ABS x ETS x EFS x EDS x
BWxATx365days/yr
ADDsc= Average Daily Dose
via soil contact
Cs = Chemical concentration in soil
(milligrams/kilogram)
SSAs = Skin surface area
(centimeters2/hr)
AF = Soil adherence factor
(rnilligram/centimeter2)
ABS = Dermal absorption factor
(unitless)
ETS = Exposure time
(hours/day)
EFS = Exposure frequency
(days/year)
EDS = Exposure duration
(years)
1CT6 = Conversion factor
(kilograms/milligram)
BW = Body weight
(kilograms)
AT = Averaging time
(yearsj
Equation 2-5
Dermal Contact with Water
ADD™ =
Tw x IP'3 x EVW x EFW x EDW x SSAW
BWxATx365days/yr
(steady state equation - see text for discussion of non-steady state approach)
ADDwc = Average Daily Dose
via water contact
= Chemical concentration in water
(milligrams/liter)
= Dermal permeability constant
(centimeters/hour)
SSAW = Skin surface area
(centimeters2)
Tw = duration of event (hr/event)
EVW = Event frequency
(events/day)
EFW = Exposure frequency
(days/year)
EDw = Exposure duration
(years)
10~3 = Conversion factor
(liters/centimeters3)
BW = Body weight
(kilograms)
AT = Averaging time
(years)
environmental, lifestyle, and genetic differences among humans and other organisms. Examples of
variability include physiological variation such as differences in body weight, breathing rate, and
the amount of food and water consumed. Environmental variation may include fluctuations in air
temperature, wind speed and direction, and soil conditions, all of which can affect the
concentration of a chemical in a specific medium in the environment and thus the average
concentration term that is used in the dose equation. Variability is usually not reducible by further
measurement or study (although it can be better characterized).
21
-------
Finally, different methods are used for inorganic and organic chemicals to calculate the
amounts of these chemicals that are absorbed from water (EPA, 1992). The method for inorganic
chemicals assumes a "steady-state" approach whereas the method for organic chemicals assumes a
"nonsteady-state" approach. Steady-state means that the system reaches equilibrium over time
and then does not change or changes only negligibly over the measurement time period. In
general, the nonsteady-state approach is believed to most accurately reflect normal human
exposure conditions since the short contact times associated with bathing and swimming generally
mean that steady-state (equilibrium) conditions will not occur. The nonsteady-state method also
accounts for the dose that can occur after the actual exposure event due to absorption of
contaminants stored in fats and oils in the skin. Application of this method requires that the
chemical in question partition between an organic solvent (octanol) and water. Inorganics do not
exhibit this characteristic and thus the nonsteady-state methodology is not applicable to
inorganics. The steady-state approach is therefore currently recommended for inorganics.
2.1.4 Risk Characterization
Risk characterization combines the assessments of hazard, dose-response, and exposure to
estimate the probability of specific harm to an exposed individual or population. It assesses the
overall quality of the information in the assessment, identifying any sources of uncertainty
associated with the risk assessment, and it indicates whether the assumptions made in the
preceding steps tend to under- or over-estimate the level of risk.
Cancer risks are expressed as probabilities. As presented here the risk equations estimate
the upper bound incremental increase in cancer risk over a lifetime due to the described exposure
scenario. Because the calculated risks are upper bound estimates, the actual risks are unlikely to
be greater. The calculated risks are the incremental increase over the "background" cancer rate
among persons living in the U.S. The current U.S. background rate for all cancers over a lifetime
is 30 about percent (i.e., 30 persons in 100 will be diagnosed with some form of cancer in their
lifetime). The calculated risk due to the chemical exposure is the additional risk (e.g., one in a
thousand, ten in a million, one in a million) above this lifetime background level.
For noncancer health effects the RfD or RfC is compared to the calculated dose or exposure
concentration. When the exposure dose divided by the RfD or the exposure concentration
divided by the RfC is greater than one (the calculated values are called "hazard quotients"), some
potential for harmful health effects exists.
The general equations for the calculation of risk for carcinogens and hazard for
noncarcinogens are as follows:
Risk via air inhalation
risk = unit risk*Ca*(InhRa/0.83)*(EFa/365)*(ETa/24)*(EDa/70)*(70/BW)2/3
HQ=
22
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Where:
Ca = Concentration in air
InhRa = Inhalation rate (meter3/hour)
EFa = Exposure frequency (days/year)
ETa = Exposure time (hours/day)
EDa = Exposure duration (years)
BW = Body weight (kilograms)
HQ = Hazard quotient
RfC = Reference concentration (may require adjusting from published value to account for
populations that differ from default EPA exposure scenarios)
Risk via ingestion of soil
risk = oral slope factor*Cs*(IRs*EFs*EDs*CFs)/(BW*ATcarc)
HQ = [Cs*(IRs*EFs*EDs*CFs)/(BW*AT*365days/year)]/RfD
Where:
Cs = Concentration in soil
IRs = Intake rate for soil (milligrams/day)
EFS = Exposure frequency (days/year)
EDS = Exposure duration (years)
CFS = Conversion factor (10"6 kilograms/milligrani)
BW = Body weight (kilograms)
ATcarc = Averaging time for carcinogens (25,550 days)
HQ = Hazard quotient
RfD = Reference dose
AT = Averaging time for noncarcinogens, equal to exposure duration (years)
Risk via ingestion of water
risk - oral slope factor*Cw*(IRw*EFw*EDw)/(BW*ATcare)
HQ = [Cw*(IRw*EFw*EDw)/(BW*AT)]/RfD
Where:
Cw = Concentration in water
IRW = Intake rate for water (liters/day)
EFW = Exposure frequency (days/year)
EDW = Exposure duration (years)
BW = Body weight (kilograms)
ATcarc = Averaging time for carcinogens (25,550 days)
HQ = Hazard quotient
RfD = Reference dose
AT = Averaging time for noncarcinogens, equal to exposure duration (years)
23
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Risk via dermal contact with water (steady-state conditions)
risk = oral slope factor*(Cw*Kp*Tw*CFw)*(EVw*EFw*EDw*SSAw)/(BW*ATcarc)
HQ = [(Cw*Kp*Tw*CFw)*(EVw*EFw*EDw*SSAw)/(BW*AT*365days/year)]/RfD
Where:
Cw = Concentration in water (milligrams/liter)
Kp = Dermal permeability (centimeters/hour)
Tw = Duration of event (hours/event)
CFW = Conversion factor (10~3 liters/centimeter3)
EVW = Event frequency (events/day)
EFW = Exposure frequency (days/year)
EDW = Exposure duration (years)
SSAW = Exposed skin surface area (centimeter2)
BW = Body weight (kilograms)
ATcare = Averaging time for carcinogens (25,550 days)
HQ = Hazard quotient
RfD = Reference dose
AT = Averaging time for noncarcinogens, equal to exposure duration (years)
Risk via dermal contact with soil/dirt
risk = oral slope factor* Cs*(SSAs*AFs*0.01*ETs*EFs*EDs*CFs)/(BW*ATcarc)
HQ = [Cs*(SSAs*AFs*0.01*ETs*EFs*EDs*CFs)/(BW*AT*365days/year)]/RfD
Where:
Cs = Concentration in water (milligrams/liter)
SSAs = Exposed skin surface area (meter2)
AFS = Soil adherence factor (unitless)
ETS = Exposure time (hours/day)
EFS = Exposure frequency (days/year)
EDS = Exposure duration (years)
CFS = Conversion factor (10"6 kilograms/miUigram)
BW = Body weight (kilograms)
AT^ = Averaging time for carcinogens (25,550 days)
HQ = Hazard quotient
RfD = Reference dose
AT = Averaging time for noncarcinogens, equal to exposure duration
Transfer of Chemicals Between Environmental Media. In addition to the sources of
uncertainty regarding environmental concentrations, exposure factors, and toxicity values
discussed above, the estimates of risk presented here do not account for the potential transfer of
contaminants between different environmental media. For some chemicals and under some
exposure conditions, the transfer of contaminants between environmental media may represent
24
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significant exposure pathways. For example, volatile contaminants in water may be released to
the air during showering, dish washing, or other indoor household activities. The volatilized
chemical could then be inhaled. A conceptual model of a facility should be prepared prior to
performing a facility-specific risk assessment to identify those pathways of exposure that are
important for that facility.
2.2 ASSESSING RISK FOR CHROMIUM ELECTROPLATING FACILITIES
2.2.1 Hazard Identification
Chrome plating is a common process in metal finishing operations and as a result, chromium
(primarily as hexavalent chromium) is prevalent in metal finishing emissions. Eight of the top 25
most commonly used metal finishing processes use chromium and it is estimated that about 2
million pounds per year of chromium are emitted to the air (23,000 pounds), discharged in
wastewater (4,600 pounds), or disposed as wastewater sludge (900,000 pounds) or other solid
waste (1,100,000 pounds) by hard chrome operations in the U.S. (EPA, 1995a). Hexavalent
chromium is emitted during the chromium electroplating process in the form of a visible yellow
mist. The mist is composed of entrained chromic acid droplets that form when hydrogen and
oxygen gases are released from the surface of the plating solution.
Hexavalent chromium is a human carcinogen and can cause a variety of other adverse health
effects (ATSDR, 1993; IARC, 1990; EPA, 1984). Breathing in chromium can cause irritation to
the nose, such as runny nose, sneezing, itching, nosebleeds, ulcers, and, over long periods of time,
holes in the nasal septum. Respiratory system effects (e.g., asthma) and immune system effects
(e.g., allergic sensitivity from dermal exposure) have been documented (ATSDR, 1993).
2.2.2 Dose-Response Values for Hexavalent Chromium
Inhalation Unit Risk. EPA estimates that the unit risk for hexavalent chromium is 0.012
(ug/m3)"1 The IRIS database provides the following information about the derivation of the
inhalation unit risk.
"Results of occupational epidemiologic studies of chromium-exposed
workers are found to be consistent across investigators and study populations.
Dose-response relationships have been established for chromium exposure and
lung cancer. Chromium-exposed workers are exposed to both chromium III and
chromium VI compounds. Because only chromium VI has been found to be
carcinogenic in animal studies, however, it was concluded that only chromium VI
should be classified as a human carcinogen. "
The IRIS database notes that the unit risk should not be used if the air concentration of
hexavalent chromium exceeds 0.8 ng/m3 The assumption that the relationship between risk and
concentration is linear may not be appropriate above this concentration (EPA, 1997e). Both
higher and lower estimates of the inhalation unit risk for hexavalent chromium have been derived
from human epidemiological studies (DTSC, 1994b; OSHA, 1995). A discussion of the merits
25
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and weaknesses of these various estimates is outside the scope of this paper, but is noted as a
source of uncertainty in attempting to quantify human health risks.
Oral Slope Factor. The IRIS database does not contain an oral slope factor for hexavalent
chromium because EPA believes that hexavalent chromium is not carcinogenic by the oral route
of exposure. When ingested, hexavalent chromium is reduced to trivalent chromium hi the saliva
and gastric juice of the upper alimentary tract (Anderson et al., 1993 and references therein).
Because the reduction of hexavalent chromium to trivalent chromium is relatively rapid and
because trivalent chromium is not carcinogenic in animals EPA believes that ingested hexavalent
chromium is not carcinogenic (EPA, 199la). However, there is some disagreement with this
conclusion and at least one state, California, has provisionally derived an oral slope factor of 4.2 x
10"1 for hexavalent chromium.
Reference Concentration. EPA does not currently list a RfC for hexavalent chromium. In
1991, EPA proposed a RfC of 0.002 ug/m3 for both hexavalent and trivalent chromium (EPA,
1991b), but this value has been withdrawn and the RfC for hexavalent and trivalent chromium are
currently under review. It has been argued by Finley, et al. (1992) that separate RfCs should be
established for the different valence states as well as for the different forms (particulates versus
acidic mists) of chromium since they present different toxicological profiles. They proposed
alternative RfCs of 1.2 and 0.12 ug/m3 for hexavalent chromium particulates and acidic mists,
respectively.
Reference Dose. EPA's RfD for soluble salts of hexavalent chromium, such as potassium
and sodium dichromates and potassium and sodium chromates, is 0.005 mg/kg»day. This value
was derived from a chronic (1-year) drinking water study in rats in which no adverse health
effects were observed hi the test animals over the treatment period. Similar "no-effect" levels
have been observed in dogs and humans (EPA, 1997e). An uncertainty factor (margin of safety)
of 500 was applied to the experimental "no-effect" dose in the rat study. The IRIS database notes:
"Confidence in the chosen study is low because of the small number of
animals tested, the small number of parameters measured and the lack of toxic
effect at the highest dose tested. Confidence in the data base is low because the
supporting studies are of equally low quality, and teratogenic and reproductive
endpoints are not -well studied. Low confidence in the RfD follows. "
Dermal Toxicity Values. Because there are few toxicity data for chemicals administered
to the skin of laboratory animals or humans, toxicity via dermal exposure is often evaluated using
oral RfDs or slope factors (EPA, 1992). This introduces a degree of uncertainty hi risk estimates
because chemicals introduced via the oral route may behave differently than if introduced through
the skin. Since pharmacokinetic data are not available for most chemicals to help interpret or
correct for potential differences hi chemical behavior/toxicity, it is often uncertain how the use of
oral toxicity factors may affect the estimate of true risk from dermal exposure. The oral RfD for
hexavalent chromium is used to assess the potential noncarcinogenic risk that can result from
dermal exposure.
26
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2.2.3 Exposure Assessment
Two worker and two residential exposure scenarios that include possible exposures via
inhalation, ingestion of drinking water, incidental ingestion of soil or other dirt (e.g., through
contamination of hands and subsequent hand to mouth actions), and dermal contact are evaluated
(Figures 2-3 and 2-4). Two levels of hexavalent chromium concentrations were selected for each
medium in the example risk assessments from among values reported in the scientific literature
(Table 2-5).
Table 2-5
Environmental Concentrations of Hexavalent Chromium Used in the
Example Risk Assessment
Concentration Level 1
Concentration Level 2
Environmental Medium
Air
Workers
0.5 ng/m3
5|ig/m3
Residents
1 ng/m3
5 ng/m3
Water
Workers/Residents
0.02 ng/L
0.2ng/L
Soil/Dirt
Workers/Residents
0.4 mg/kg
4.0 mg/kg
Although some professional judgment was used to estimate worker exposures and "typical"
residential exposures, data used in the example risk assessment for an electroplating facility are
based generally on population information compiled by EPA (EPA, 1989). The values used in the
calculation of risk estimates (Section 2.2.4) are summarized in Table 2-6. These values represent
only a few of the possible exposure scenarios. Actual exposures would vary among individual
facilities. For the dermal exposure pathway a dermal permeability factor, Kp, is needed to
determine exposure dose. A Kp of 2.0 x 10"3 cm/hr, the recommended value for sodium
chromate, is used (EPA, 1992). This value was selected by EPA because it was reported in
several studies using both human and animal subjects. Experimentally-derived Kp values ranging
from 3.1 x 10 to 1.2 x 10 cm/hr have been reported for other chromium compounds.
Concentrations in Workplace Air. OSHA's Integrated Management Information System
(IMIS) database contains the results of 424 personal, full-shift air samples that were collected
between 1979 and 1993 and were analyzed for hexavalent chromium (Table 2-7). These samples
were collected in industry sectors classified in SIC Codes 33 through 39 and represent 8-hour
TWA exposure of employees with job titles such as "plater," "plating operator," "electroplater,"
and "anodizer." Almost two-thirds of the IMIS samples were obtained in industry sectors within
SIC Code 3471. Approximately 92% of the values were less than 10 ug/m3 and almost 75% were
less than 1.0 ug/m3 OSHA is currently considering a new workplace exposure limit for
hexavalent chromium in the range of 0.5 to 5.0 ug/m3 (Freeman and Condit, 1995). Workplace
concentrations of 0.5 ng/m3 and 5.0 M-g/m3 are used in the example risk assessment calculations.
27
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Table 2-6
Summary of Exposure Factors Used in Example Risk Assessment
Air
Scenario Name
adult resident-Scenario 2
adult resident-Scenario 1
child resident-Scenario 2
child resident-Scenario 1
worker-Scenario 2
worker-Scenario 1
Water
Scenario Name
adult resident-Scenario 2
adult resident-Scenario 1
child resident-Scenario 2
child resident-Scenario 1
worker-Scenario 2
worker-Scenario 1
Soil/Dirt
Scenario Name
adult resident-Scenario 2
adult resident-Scenario 1
child resident-Scenario 2
child resident-Scenario 1
worker-Scenario 2
worker-Scenario 1
Inhalation Rate
0.83
0.63
0.42
0.36
0.83
0.63
m3/hour
m3/hour
m'/hour
m3/hour
m3/hour
m3/hour
Intake Rate
2.4
1.4
1.3
0.7
2.4
1.4
L/day
L/day
L/day
L/day
L/day
L/day
Intake Rate
100
50
400
200
100
50
mg/day
mg/day
mg/day
mg/day
mg/day
mg/day
Exposure Frequency
350
340
350
340
250
240
days/year
days/year
days/year
days/year
days/year
days/year
Exposure Frequency
350
340
350
340
250
240
days/year
days/year
days/year
days/year
days/year
days/year
Exposure Frequency
350
275
350
275
250
240
days/year
days /year
days/year
days/year
days/year
days /year
Exposure Time
24
16
24
16
8
8
hours/day
hours/day
hours/day
hours/day
hours/day
hours/day
Exposure Time
0.25
0.17
0.14
0.11
0.50
0.25
hours/day
hours/day
hours/day
hours/day
hours/day
hours/day
Exposure Time
23
16
23
16
8
8
hrs/day
hrs/day
hrs/day
hrs/day
hrs/day
hrs/day
Exposure Duration
24
7
6
2
25
7
years
years
years
years
years
years
Exposure Duration
24
7
6
2
25
7
years
years
years
years
years
years
Exposure Duration
24
7
6
2
25
7
years
years
years
years
years
years
Skin Surface Area
23,000
20,000
9,180
7,930
4,290
3,190
cm2
cm2
cm2
cm2
cm1
cm2
Skin Surface Area
5.800
6,000
2,300
1,980
4,290
3,190
cm2/hr
cm2/hr
cm2/hr
cm2/hr
cm!/hr
cm2/hr
Averaging Time
24
7
6
2
25
7
years
years
years
years
years
years
Averaging Time
24
7
6
2
25
7
. years
years
years
years
years
years
Averaging Time
24
7
6
2
25
7
years
years
years
years
years
years
Body Weight
70
70
15
15
70
70
kg
kg
kg
kg
kg
kg
Body Weight
70
70
15
15
70
70
kg
kg
kg
kg
kg
kg
Body Weight
70
70
15
15
70
70
kg
kg
kg
kg
kg
kg
Soil Adherence Factor
AFelRMe
AFelcr
1.0
0.2
Averaging Time
AT
" ' cauinogens al
Kp
70
0.002
mg/cm2
mg/cm2
years
cm/hr
28
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Note that the higher concentration exceeds the recommended upper concentration limit for use
with EPA's unit risk as described in Section 2.2.2.
Table 2-7
Relative Proportion of Hexavalent Chromium Concentrations
Measured in the Workplace
Concentration in Air (jig/m3)
<0.1
70%
0.1 -1.0
3.5%
1.0-2.0
2.8%
2.0 - 5.0
8.5%
5.0 - 10.0
6.8%
10.0-50.0
6.4%
>50.0
2.6%
Total does not equal 100% due to rounding.
Concentrations in Ambient Air. Measurements of atmospheric hexavalent chromium hi a
non-industrial area of New Jersey ranged from 0.2 to 3.8 nanograms (ng)/m3, with a mean of 1.2
ng/m3 (Finley, et al., 1995). Measurements hi 20 California cities reportedly ranged from less than
0.2 to 9 ng/m3 with a majority of samples at about 1 ng/m3 (Finley, et al., 1996). A recent
Canadian study reported atmospheric concentrations of 0.1 to 1.6 ng/m3, with a geometric mean
of 0.55 ng/m3 (Bell and ffipfher, 1997). The Canadian study also cites other works that indicate a
hexavalent chromium concentration hi the range of 1 to 5 ng/m3 hi urban areas. Ambient air
concentrations of 1 and 5 ng/m3 are used in the example risk assessment calculations for the
residential exposure scenario. These concentrations represent the estimated current background
concentration of hexavalent chromium from natural and anthropogenic (human-related) sources,
which may include some contribution of chromium from plating facilities. Concentrations of
hexavalent chromium may be higher than background in the vicinity of chromium plating facilities.
Any increase hi concentration that results from emissions would result hi an incremental increase
hi risk for exposed populations. As noted above, air concentrations can be determined by
dispersion modeling or by measurement.
Concentrations in Drinking Water. A survey of tap water hi the United States conducted
during the 1970s found that the concentration of total chromium ranged from 0.4 to 8.0 ug/L,
with a mean of 1.8 ^g/L (ATSDR, 1993). ATSDR notes that these values may be higher than the
actual values, due to inadequate flushing of tap water before sample collection. In addition,
because the values are for total chromium, hexavalent chromium would be expected to be some
percentage of the total chromium concentration. Hexavalent chromium concentrations of 0.02
and 0.2 ug/L, approximately 1% and 10% of the mean total chromium concentration hi the cited
study, are used hi the example risk assessment calculations for both the worker and residential
exposure scenarios.
Concentrations in Soils. The natural chromium concentrations hi soils vary greatly and
depend on the composition of the parent rock from which the soils were formed. The trivalent
form of chromium predominates hi most soils (ATSDR, 1993). A study of soils hi the United
States by the United States Geologic Survey (USGS, 1984) reported that the concentration of
total chromium ranged from 1 to 2,000 mg/kg, with a geometric mean of 37 mg/kg. A Canadian
29
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Figure 2-3
Exposure Scenarios for Workers
Air Emissions
Ventilation
Treatment System
• Mist" .
formation'
Fugitive
Emissions
Plating Bath
Spills
Inhalation
Ingestion
Dermal
Contact
Water Treatment
System
7-Year Worker
Exposure Scenario
8-hour work day
40-hour work week
4 weeks of leave per year
7 years on the job
Moderate breathing rate and
water consumption at
typical exertion level
Air Emissions
Ventilation
Treatment System
f
Inhalation
• Mist .
formation'
Fugitive ^ Ingestion
Emissions Jj
Plating Bath
Spills
Dermal
Contact
Water Treatment
System
25-Year Worker
Exposure Scenario
8-hour work day
40-hour work week
2 weeks of leave per year
25 years on the job
Elevated breathing rate and
water consumption at
above average exertion level
30
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Figure 2-4
Exposure Scenarios for Residents
Air Emissions
ventilation
Treatment System
9-Year Resident Exposure Scenario
16 hours per day
340 days/year (about 4 weeks away
from home)
2 years as a child plus 7 years
as an adult for carcinogens OR
2 years as a child for noncarcinogens
(see text for explanation)
Breathing rate and water consumption
at average levels
Inhalation
Ingestion
Dermal
Contact
Air Emissions
Ventilation
Treatment System
30-Year Resident Exposure Scenario
24 hours per day
350 days/year (about 2 weeks away
from home)
6 years as a child plus 24 years
as an adult for carcinogens OR
6 years as a child for noncarcinogens
(see text for explanation)
Breathing rate and water consumption
at above average levels
Inhalation
Ingestion
Dermal
Contact
31
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study reported concentrations that ranged from 5 to 1,500 mg/kg, with a mean of 43 mg/kg
(ATSDR, 1993). Hexavalent chromium concentrations of 0.4 and 4 mg/kg, approximately 1%
and 10% of the mean total chromium concentration in the two cited studies, are used in the
example risk assessment calculations for both the worker and residential exposure scenarios.
The estimate of workplace exposure via dermal pathways contains a great deal of
uncertainty because concentrations of hexavalent chromium in the work environment are highly
dependent upon the effectiveness of industrial hygiene practices applied in the workplace. While
concentrations of chromium on surfaces near electroplating tanks may be high, the use of
personnel protective equipment such as gloves would greatly reduce exposure via dermal contact.
2.2.4 Risk Characterization
Using the input variables for toxicity, exposure and environmental concentrations described
in the preceding sections, estimated excess cancer risks and hazard quotients have been calculated
for exposure to hexavalent chromium in two settings, a workplace exposure scenario and a
residential exposure scenario. For each of the two exposure settings the exposure factors (e.g.,
inhalation rates, exposure time, exposure duration) and environmental concentrations of
hexavalent chromium were varied to yield a total of four estimates of cancer risk and assessments
of the potential for adverse health effects due to noncarcinogenic effects. Estimates of excess
cancer risks to residents were calculated using the assumption that exposure occurred over a
period of time that includes both adult and childhood exposure. Hazard quotients for residents
were calculated using exposure factors for children only. Hazard quotients for children are higher
than for adults (at exposure to equivalent environmental concentrations) because children have
lower body weights and higher intakes via certain pathways (e.g., ingestion of soil) than adults.
Calculations were performed by entering example exposure data (Section 2.1.3), example
environmental concentrations (Section 2.1.4), and risk equations (Section 2.1.4) onto a computer-
based spreadsheet in Microsoft® Excel.
Residential Exposure Scenario. The four estimates of total lifetime excess cancer risk
(Table 2-8 and Figure 2-5) for residential exposures are calculated for hypothetical 9- and 30-
year exposures (Table 2-5) at the lower and upper environmental concentrations (Table 2-6). The
9-year exposure assumes that the exposed individual is present for 2 years as a child and 7 years
as an adult. The 30-year exposure assumes that the exposed individual is present for 6 years as a
child and 24 years as an adult. The scenarios yield estimates of total lifetime excess cancer risks
that range from 8.3 x 10~7 to 2.7 x 10~5 All of this risk is derived from the inhalation pathway
because hexavalent chromium is not believed to be carcinogenic by ingestion or dermal uptake.
Because the risk calculation for the inhalation pathway uses a hexavalent chromium concentration
in air that has been reported for several urban areas, these values reflect a minimum (background)
estimate of risk for the inhalation route of exposure that can be calculated using this methodology
and the exposure factors presented herein.
The hazard quotients for the residential exposures are all well below unity, indicating that
concentrations of hexavalent chromium for these exposure scenarios would not present a
noncancer health hazard.
32
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Table 2-8
Predicted Lifetime Excess Cancer Risks and Hazard Quotients
for Exposure to Hexavalent Chromium
Excess Cancer Risks
Concentration Level 1
Concentration Level 2
Worker Exposure Scenario
7-Year Exposure
2.0 x W4
*
25-Year Exposure
4.3 x 1(T3
*
Resident Exposure Scenario
9-Year Exposure
8.3 x 1CT7
4.1x10^
30-Year Exposure
5.3 x 1CT6
2.7 x 1CT5
* Concentration of hexavalent chromium exceeds valid range for calculating risk using EPA's unit risk value.
Hazard Quotients for Noncarcinogens
Concentration Level 1
Concentration Level 2
Worker Exposure Scenario
7-Year Exposure
<.001
.001
25-Year Exposure
<.001
.004
Resident Child Exposure Scenario
2-Year Exposure
.001
.012
6-Year Exposure
.003
.029
There is uncertainty associated with the environmental concentrations of hexavalent
chromium in water and soil. While several estimates of hexavalent chromium concentrations in air
were available in the scientific literature, the values for water and soil are based on percentages of
measured values for total chromium. As actual concentrations may be higher or lower, it is
uncertain how the use of these estimates may affect the estimate of risk from oral and dermal
exposures. Direct measurement of facility-specific concentrations would reduce the uncertainty
associated with exposure point concentrations.
Worker Exposure Scenario. Two estimates of total lifetime excess cancer risk for
workplace exposures are calculated for hypothetical 7- and 25-year worker exposures at the
lower environmental concentration. No excess cancer risk is included for the highest workplace
air concentration because it exceeds 0.8 fig/nf, the maximum concentration for which EPA
considers its unit risk to be valid. The scenarios yield estimates of lifetime excess cancer risks that
range from 2.0 x 10"4 to 4.3 x 10"3. As is the case for the residential exposure, all of this risk is
derived from the inhalation pathway.
Although the workplace estimates of risk are higher than that usually associated with
environmental exposures (EPA generally regulates carcinogens in the range of one in ten thousand
[1 x 10"*] to one in a million [1 x 10"6] chances of excess cancer risk), the estimated risks are
similar to the one in a thousand (1 x 10~J) risk level that OSHA considers a "significant" risk when
33
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making risk management decisions to regulate workplace carcinogens. However, OSHA's
estimates of risk are not directly comparable to these estimates because OSHA assumes an 8-hour
day and a 240-day work-year over a 45-year working lifetime and because OSHA develops its
own cancer potency factors, which may differ from EPA's (Rhomberg, 1996). Actual workplace
concentrations and exposure factors would vary among facilities and would depend upon many
factors including the operation and maintenance of ventilation systems, administrative controls to
limit worker exposures, and the use of personnel protective equipment. Direct measurement of
chromium concentrations within workers' breathing zones would reduce uncertainty associated
with worker exposures.
Figure 2-5
Lifetime Excess Cancer Risk for Community Residents
for Example Risk Assessment
3.0E-05
cr
o
c
CO
O
in
in
x
HI
9-Yr Exposure
Low Cone. Levels
9-Yr. Exposure
Upper Cone. Levels
30-Yr. Exposure
Low Cone. Levels
30-Yr. Exposure
Upper Cone. Level.
Residential Exposure Scenario
2.3 RISK COMMUNICATION
Risk assessments should be prepared with potential risk managers and stakeholders in mind,
to assure that appropriate information will be provided in a format that is understandable and
useable to all interested parties. An appropriate level of detail for data presentation and reports
should be identified early in the process because potential risk managers are a diverse group that
may have varying degrees of technical expertise. Presenting risk assessment results in a clear and
concise format increases the likelihood that risk managers will remain engaged in the process and
will contribute input on political, social, and economic issues that are part of the risk management
process.
34
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This paper presents example exposure scenarios and identifies the data inputs (i.e.,
environmental concentrations, measures of exposure, and toxicity information) that are needed to
assess the potential health risks to workers and residential populations that are exposed to
chemical emissions from metal finishing facilities. Such risk-based information is desired by
stakeholders within EPA's CSI Metal Finishing Sector but has not been made widely available to
them. While some emissions data for metal finishing facilities are available, translation of that
information into statements about potential health effects of those emissions has been limited.
Risk-based information is needed to assist risk managers and stakeholders in identifying important
risks, so that they may prioritize those risks and allocate resources to address them. Success of
the risk assessment approach in meeting the need of risk managers to understand the health risks
associated with facility emissions requires that risk managers be informed about the risk
assessment process. The elucidation of the methods of risk assessment as described herein is an
important starting point for the necessary dialog between risk managers and stakeholders involved
with the Metal Finishing Sector, and the risk assessor.
35
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3. SUMMARY
Facility-based risk characterization for workers and surrounding communities is a high
priority issue for stakeholders in EPA's CSI Metal Finishing Sector. Platers, environmental
groups, community groups, labor, and regulators all need and want to know what emissions are
coming out and in what amounts from metal finishing operations (EPA, 1997a). They also want
to know what health risks those emissions create for workers and the surrounding communities.
Potential health risks from emissions can be described and quantified by the process of risk
assessment. Risk assessment evaluates information on the hazardous properties of chemicals and
the extent of human exposure, and characterizes the resulting risks. EPA and others use a risk
assessment process formalized by the National Academy of Sciences that is comprised of four
steps—hazard identification, dose-response assessment, exposure assessment, and risk
characterization (NRC, 1983; 1994).
The Research and Technology Work Group of the CSI Metal Finishing Subcommittee
identified the development and application of simple methods to characterize the emissions from
plating operations as a high priority item in its R&D Plan (EPA, 1997a). Specifically, the R&D
Plan recommended characterizing the emissions from plating operations and from them the risks
to workers, surrounding communities, and the environment. The objectives of this project were
to address the recommendation of the R&D Plan by 1) identifying the types and sources of
information needed to assess risks to workers and surrounding communities from metal finishing
facilities (hazard identification and dose-response assessment), 2) developing a general facility
model that describes potential human exposure pathways (exposure assessment), 3) presenting
equations that characterize the exposure pathways from emission sources to workers and the
public, and 4) quantifying the lifetime excess cancer risk and potential for other health hazards
from hexavalent chromium in a screening risk assessment process (risk characterization).
By explaining the steps performed and the data needed to conduct a risk assessment it is
hoped that this paper will assist those associated with the industry to better understand the risk
assessment process and the questions that can be answered by the process. Based on the work
reported here, it is concluded that the general methodology for carrying out risk assessments for
metal finishing workers and surrounding communities is known; that it is possible to calculate
such risks for a number of worker and community scenarios, and that the methodology has
limitations associated with toxicity information for chemicals used in the metal finishing sector and
with exposure inputs, such as environmental concentrations of chemicals and activity patterns of
potentially exposed individuals.
Important needs for additional development of this approach to facility-based risk
characterization for hard chromium plating and other operations are:
• communication between risk managers, stakeholders, and risk assessors to identify
issues of greatest importance to end users of the risk assessment information;
• determination of environmental concentrations of chemical emissions of interest (either
modeled or measured) for use in risk assessments; and
• refinement of exposure information for potentially exposed populations.
36
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4. REFERENCES
Anderson, R.A., T. Colton, J. Doull, J.G. Marks, and R.G. Smith, 1993. Designing a
biological monitoring program to assess community exposure to chromium: conclusions of an
expert panel. Journal of Toxicology and Environmental Health 40:555-583.
ATSDR, 1993. Toxicological Profile for Chromium. Prepared by Syracuse Research
Corporation under subcontract to Clement International Corporation for the Agency for Toxic
Substances and Disease Registry, Public Health Service, United States Department of Health and
Human Services.
Bell, R.W., and J.C. Hipfher, 1997. Airborne hexavalent chromium in southwestern
Ontario. J. Air & Waste Management 47:905-910.
Browner, Carol M, 1994. Speech delivered by Carol M. Browner, Administrator, United
States Environmental Protection Agency, at the Center for National Policy Newsmaker
Luncheon, Washington, D.C. July 20.
CAMP, 1995. Profile for the Metal Finishing Industry-Draft. Prepared for the Cleveland
Advanced Manufacturing Program (CAMP) under contract to the Energy Environment and
Manufacturing project of the Technology Reinvestment Program (EEM-TRP). Waste Reduction
Institute for Training and Applications Research (WRITAR).
DTSC (California Department of Toxic Substances Control), 1994a. Preliminary
Endangerment Assessment Guidance, January.
DTSC, 1994b. California Cancer Potency Factors, California Department of Toxic
Substances Control, Standards and Criteria Work Group. 1 November.
EPA, 1984. Health Assessment Document for Chromium. Final Report. EPA-600/8-83-
014F. Environmental Criteria and Assessment Office, Research Triangle Park, North Carolina.
NTISPB85-115905.
EPA, 1986. Guidelines for Carcinogen Risk Assessment. 51 Federal Register 33992-
34003.
EPA, 1989. Exposure Factors Handbook. United States Environmental Protection
Agency, Office of Research and Development. EPA/600/8-89/043. May (a preliminary draft
revision of this document was released for comment in August 1996).
EPA, 199la. National Primary Drinking Water Regulations, Final Rule. Code of Federal
Regulations 40: Parts 141,142, and 143, January 30.
EPA, 1991b. Health Effects Assessment Summary Tables, FY-1991. Publ. No. OERR
9200, 6-303 (91-1) United States Environmental Protection Agency, Office of Emergency and
Remedial Response, Washington, D.C.
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EPA, 1992. Dermal Exposure Assessment: Principles and Applications, Interim Report.
United States Environmental Protection Agency, Office of Research and Development.
EPA/600/8-91/01 IB.
EPA, 1993. Introduction to IRIS. August 18.
EPA, 1994. A New Generation of Environmental Protection. CSI: Administrator's
Update, Number 12. July 29.
EPA, 1995a. Draft Report on Emissions from Metal Finishing Operations. United States
Environmental Protection Agency, Office of Research and Development. March 31.
EPA, 1995b. Health Effects Assessment Summary Tables. United States Environmental
Protection Agency, Office of Emergency and Remedial Response, Washington, D.C. May.
EPA, 1995c. Profile of the Fabricated Metal Products Industry. Office of Compliance
Sector Notebook Project, United States Environmental Protection Agency, Office of Enforcement
and Compliance Assurance. September.
EPA, 1995d. Pollution Prevention Assessment for a Manufacturer of Electroplated Truck
Bumpers. United States Environmental Protection Agency, National Risk Management Research
Laboratory. September.
EPA, 1996a. Proposed Guidelines for Carcinogen Risk Assessment, 61 Federal Register
17960, April 23.
EPA, 1996b. Proposed Guidelines for Ecological Risk Assessment, 61 Federal Register
47552, September 9.
EPA, 1997a. National Metal Finishing Environmental R&D Plan. Common Sense
Initiative Metal Finishing Subcommittee. January 7.
EPA, 1997b. Discussion Draft, Strategic Goals Program, Part 1: National Performance
Goals, Part 2: Action Plan. Common Sense Initiative, Metal Finishing Sector. July 15.
EPA, 1997c. 1995 Toxics Release Inventory Public Data Release. United States
Environmental Protection Agency, Office of Prevention, Pesticides and Toxic Substances. EPA
745-R-97-005. April.
EPA, 1997d. Common Sense Initiative. Metal Finishing Sector Fact Sheet. United States
Environmental Protection Agency. EPA 742-B-96-007. March.
EPA, 1997e. Integrated Risk Information System. National Center for Environmental
Assessment. Downloaded from National Library of Medicine on-line service. July.
38
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Finley, B.L., D.M. Proctor, and D.J. Paustenbach, 1992. An alternative to EPA's proposed
inhalation reference concentrations for hexavalent and trivalent chromium. Regulatory Toxicology
and Pharmacology 16:161-176.
Finley, B.L., B.D. Kerger, D.G. Dodge, S.M. Meyers, R.O. Richter, and D.J. Paustenbach,
1996. Assessment of airborne hexavalent chromium in the home following use of contaminated
tapwater. J. Exposure Analysis and Environ. Epidemiol. 6:229-245.
Freeman, C., and K. Condit, 1995. The new OSHA regulations for hexavalent chromium.
16th AESF/EPA Pollution Prevention & Control Conference Proceedings. 13-15 February.
IARC (International Agency for Research on Cancer, 1990. Chromium and Chromium
Compounds. IARC Monograph Series, World Health Organization, Volume 49.
Klaasen, C.D., 1995. Casarett and Doull's Toxicology, The Basic Science of Poisons,
McGraw-Hill, Health Publications Division, New York.
Murphy, M., (ed.), 1996. Metal Finishing: 64th Guidebook and Directory Issue, Vol. 94,
No. 1 A. Elsevier, New York.
NCMS (National Center for Manufacturing Sciences), 1994. Pollution Prevention and
Control Technology for Plating Operations. Prepared for the National Center for Manufacturing
Sciences and the National Association of Metal Finishers, George Cushnie.
NRC (National Research Council), 1983. Risk Assessment in the Federal Government:
Managing the Process. National Academy Press, Washington, D.C.
NRC, 1994. Science and Judgment in Risk Assessment. National Academy Press,
Washington, D.C.
OSHA (Occupational Safety and Health Administration), 1995. Evaluation of
Epidemiological Data and Risk Assessment for Hexavalent Chromium. Prepared for OSHA by
K.S. Crump Division, ICF Kaiser. OSHA Hexavalent Chromium Docket, Docket H-054A,
Exhibit #13-5.
Presidential/Congressional Commission on Risk Assessment and Risk Management, 1997a.
Final Report, Volume 1, Framework for Environmental Health Risk Management.
Presidential/Congressional Commission on Risk Assessment and Risk Management, 1997b.
Final Report, Volume 2, Risk Assessment and Risk Management in Regulatory Decision-Making.
Puri, I.K., 1993. The Metal Products and Machinery Industry - Issues for Pollution
Reduction. Produced in cooperation with Paul Shapiro, United States Environmental Protection
Agency, Office of Environmental Engineering and Technology Demonstration through an
American Association for the Advancement of Science Summer Environmental Science and
Engineering Fellowship. August 9.
39
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Rhomberg, L.R., 1996. A survey of methods for chemical health risk assessment among
federal regulatory agencies, prepared at the request of the Presidential/Congressional
Commission on Risk Assessment and Risk Management.
Schaum, J., 1997. Personal communication with John Schaum, National Center for
Environmental Assessment, United States Environmental Protection Agency.
Thistle Publishing, 1996. Risk Assistant™, version 1.1, Alexandria, VA.
USGS (United States Geological Survey), 1984. Element Concentrations in Soils and
Other Surficial Materials of the Conterminous United States. USGS Professional Paper 1270.
40
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ACRONYMS
AAAS = American Association for the Advancement of
Science
ABS = dermal absorption factor
AF = soil adherence factor
ADD = average daily dose
AESF = The American Electroplaters and Surface
Finisher's Society, Inc.
AMSA = Association of Municipal Sewerage Agencies
AT = averaging time
ATSDR = Agency for Toxic Substances and Disease
Registry
BW = body weight
Ca = concentration in air
Cs = concentration in soil
Cw = concentration in water
CAMP = Cleveland Advanced Manufacturing Program
care = carcinogen
cm = centimeter
CSI = Common Sense Initiative
DTSC = Department of Toxic Substances Control
(California)
ED = exposure duration
EF = exposure frequency
EPA = Environmental Protection Agency (US)
ET = exposure time
EV = event frequency
HQ = Hazard quotient
hr = hour
LARC = International Agency for Research on Cancer
EVQS = Integrated Management Information System
IR = intake rate
InhR = inhalation rate
IRIS = Integrated Risk Information System
kg = kilogram
Kp = dermal permeability constant
L = liter
LOAEL = lowest-observed-adverse-effect-level
m = meter
m3 = cubic meters
mg = milligram
|o.g = microgram
NOAEL = no-observed-adverse-effect-level
NCEA = National Center for Environmental Assessment
NCMS = National Center for Manufacturing Sciences
ng = nanogram
NRC = National Research Council
NRDC = Natural Resources Defense Council
ORD = Office of Research and Development
OSHA = Occupational Safety and Health
Administration
R&D = Research and Development
RfC = Reference concentration
RfD = Reference
SF = Cancer slope factor
SIC = Standard Industry Classification
SSA = skin surface area
TWA = time-weighted average
Tw = duration of event
UAW = United Auto Workers
USGS = United States Geological Survey
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APPENDIX A
Output from Risk Assistant™
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RISK*ASSISTANT for Windows Report
R*A Standard Report 09/28/97
13:18
Approach
The procedures used by RISK*ASSISTANT to calculate exposures have been reviewed by the
Office of Health and Environmental Assessment of the U.S. EPA.Default parameters for calculating
exposures have been extracted from these U.S.EPA documents:
U.S.EPA, Office of Solid Waste and Emergency Response,Risk Assessment Guidance for
Superfund,Volume I: Human Health Evaluation Manual,Supplemental Guidance: Standard Default
Exposure Factors. Directive 9285.6-03; Interim Final. March 25, 1991.
J.Konz, K.Lisi, and E. Friebele, Exposure Factors HandbookU.S.EPA, Office of Health and
EnvironmentalAssessment, EPA/600/8-89/043; March 1989.
Aggregation Method Used, in Analysis
The following table lists the technique used to combine data from multiple samples (i.e. the
Aggregation Method) for each environmental medium included in the analysis. For each class of data
qualifier that might apply to the sample set (non-detects, estimated values, controls not within
limits, or concentration estimated at a dilution factor), the approach used to assign a
concentration to the qualified data values is presented.
Contaminated Aggregation Treatment of Qualified Samples
Medium Method NonDetect Estimated Ctls not within limitsDilution Factor
(U) (J) (R,B,E,M,N,W,*) (D)
Four options are available for dealing with qualified sample data (i.e. concentration values
for which a proxy value has been entered, accompanied by one of the four classes of data
qualifiers recognized by RISK*ASSISTANT.A separate decision can be made for each class of qualified
data. The user may either use all proxy values as entered, use one-half of the entered proxy value,
exclude (drop) the qualified data, or set the concentration for the qualified data to zero.
Chemical Concentrations in Contaminated Media
The concentration values presented in this table are expressed using the S.I. (Systeme
Internationale, also called metric) units most commonly employed in risk assessment. They may differ
from the units used in data entry.
CAS# Chemical Name
540-29-9 CHROMIUM (VI)
GW SW Air Soil Sed Veget Fruit Fish Dairy Meat
ug/1 ug/1 ug/cu m mg/kg mg/kg ug/kg ug/kg ug/kg ug/kg ug/kg
0.2 0.001 0.4
NOTE: scientific notation is used for numbers less that 0.000001 and greater than 1000000.
For example:0.00000021 = 2.1e-7 = 2.1 / 10000000 and 21000000 = 2.1e7 = 2.1 * 10000000.
GW = Groundwater, SW = Surface Water, Sed = Sediment, Veget = Vegetable.
The listed concentration in each medium for a chemical reflects the selection of sample values
employed in aggregation, the aggregation method selected,, and the approach used for dealing with
qualified data. Where concentration data were entered directly, the assessor should be prepared to
explain the values that were chosen.
Exposure Scenarios
In RISK*ASSISTANT,every exposure scenario is associated with a single contaminated medium. While
some scenarios potentially apply to more than one medium, any individual assessment must assign a
scenario to only one contaminated medium.
Groundwater
Drinking Water
Air
Indoor Air
Outdoor Air
Soil
Dust/Soil Indoors
Dust/Soil Outdoors
The dose and concentration estimates in this assessment, as well as any risk estimates that are
derived from them, refer only to the specific exposures that have been described. This description
consists of:
Contaminant concentrations in one or more environmental media.
For each contaminated medium, one or more scenarios describing how a person contacts that
medium.
Parameters that describe each scenario, both in general, and for each potential route of
exposure (oral, inhalation, or dermal).
An assessment that incorporates other exposures, or that does not incorporate all of the exposures
A-l
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described in this analysis, will yield different results. This list presents the exposure scenarios
evaluated for each contaminated medium considered in this assessment.
Cross-Media Transfer Equations Used to Generate Exposure Estimates
For some exposure scenarios a contaminant concentration specified in one environmental
medium must be converted to a concentration in another medium, to which a person is
exposed. (For example, in order to evaluate inhalation exposures while showering,
contaminant concentrations in domestic water must be converted to concentrations in
bathroom air.) The following equations were used in this assessment to predict such
cross-media contaminant transfers in each of the indicated exposure scenarios.
INHALATION OF PARTICULATES INSIDE THE RESIDENCE Soil to respirable Particulates
REFERENCES:
(1) Wark, K. & Warner, C.F.Air Pollution: Its Origin and Control,Second Ed., New York:
Harper & Row, 1981.
(2) Hawley, J.K. 'Assessment of Health Risk from Exposure to Contaminated Soil.' Risk Analysis,
5,(1985)289.
EQUATION: C(i)=D*R*f*C(s)
PARAMETERS User Value
C(i) Inhaled Concentration of Contaminant Calculated
C(s) Concentration in Soil Chemical Specific
R = Respirable Fraction of Dust 73.00%
f = Proportion of Contaminated Dust 0.80%
D = Dust Concentration 56.00 ug per cu.m
INHALATION OF PARTICULATES OUTSIDE THE RESIDENCE Soil or Sediment to respirable
Particulates
REFERENCES: Wark, K. & Warner, C.F.Air Pollution: Its Origin and Control,Second Ed.,
New York: Harper & Row, 1981.
EQUATION: C(i)=D*R*f*C(s)
PARAMETERS User Value
C(i) Inhaled Concentration of Contaminant Calculated
C(s) Concentration in Soil Chemical Specific
R = Respirable Fraction of Dust 73.00%
f = Proportion of Contaminated Dust 1.00%
D = Dust Concentration 75.00 ug per cu.m
Concentrations in Media after Transfers
For some exposure scenarios a contaminant concentration specified in one environmental medium must
be converted to a concentration in another medium, to which a person is exposed. For example, in
order to evaluate inhalation exposures while showering, contaminant concentrations in domestic water
must be converted to concentrations in bathroom air. The values presented in this table are
concentrations of contaminants in exposure media that have been predicted for specific exposure
scenarios from concentrations that were specified in other media.
Chemical Name
Contaminated Media / Scenario Calculated Concentrations
GW SW Air Soil Sed Veget Fruit Fish Dairy Meat Derm.Ab.
ug/1 ug/1 ug/cu m mg/kg mg/kg ug/kg ug/kg ug/kg ug/kg ug/kg mg/sq cm
540-29-9 CHROMIUM (VI)
Soil
Dust/Soil Indoors 1.3e-008
Dust/Soil Outdoors 2.2e-008
NOTE: scientific notation is used for numbers less that 0.000001 and greater than 1000000.
For example:0.00000021 2.1e-7 = 2.1 / 10000000 and 21000000 = 2.1e7 = 2.1 * 10000000.
GW = Groundwater, SW = Surface Water, Sed = Sediment, Veget = Vegetable.
Derm.Ab. = Dermal Absorption Rate, (1) Indicates Outside Model Bounds, (2) Indicates Missing Data
Exposure Parameters Used to Generate Exposure Estimates
The dose (or exposure concentration) values presented in this assessment reflect not only
the concentrations of contaminants in various environmental media and the exposure pathways
selected for analysis, but also the specific numerical parameters applied to each exposure
scenario. The following tables summarize the exposure parameters used in this assessment-
Population: Avg American(RME)
General Population Parameters
Body Weight: 70.00 kg
Lifetime: 70.00 years
Exposure Period: 30 years
A-2
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Scenario Specific Parameters
Scenario
Drinking Water
Indoor Air
Outdoor Air
Dust/Soil Indoors
Dust/Soil Outdoors
Scenario
Event Frequency
350 events per year
350 events per year
350 events per year
350 events per year
General Parameters
Event Duration
350
events per year
21 hours per event
3 hours per event
21 hours per event
3 hours per event
Drinking Water
Indoor Air
Outdoor Air
Dust/Soil Indoors
Dust/Soil Outdoors
ORAL
Amount
Ingested
2 litersper event
100
100
mg per event
mg per event
Fraction
Contamin.
100 %
100
100
INHALATION
Breathing
Rate
0.71 cu.m per hour
1. 67 cu.m per hour
0.71 cu.m per hour
1.67 cu.m per hour
DERMAL
Exposed
Skin Area
Average Daily Dose or Exposure Concentration
When an exposure assessment will be used as part of a quantitative risk assessment, a numerical
estimate of exposure must be calculated. The value employed for this estimate varies, according to
the route of exposure.
When evaluating the risk of chronic non-cancer health effects from oral or dermal exposures, EPA
employs the Average Daily Dose (ADD) received during the period of exposure. These are compared to
Reference Doses (RfDs). When evaluating such effects from inhalation exposure, EPA employs
contaminant concentrations, which are compared to Reference Concentrations (RfCs) for continuous
exposure.
ADD
Inh.Conc
=Average Daily Dose (during exposure period) .
Units are milligrams of contaminant per kilogram of body weight per day.
Concentration of contaminant in inhaled air.
Units are milligrams of contaminant per cubic meter of air.
Chemical Oral
Medium ADD
Scenario mg/kg/d
18540-29-9 CHROMIUM (VI)
Groundwater
Drinking Water 0.000005
TOTALS 0.000005
Air
Indoor Air
Outdoor Air
TOTALS
Soil
Dust/Soil Indoors 5.5e-007
Dust/Soil Outdoors 5.5e-007
TOTALS 0.000001
Inhalation
Concentration
mg/cu m
0.000001
0.000001
0.000002
1.3e-008
2.2e-008
3.5e-008
Dermal
ADD
mg/kg/d
NOTE: scientific notation is used for numbers less that 0.000001 and greater than 1000000.
For example:0.00000021 = 2.1e-7 = 2.1 / 10000000 and 21000000 = 2.1e7 = 2.1 * 10000000.
ADD/LADD values are meaningful up to the second significant digit.
Lifetime Average Daily Dose or Adjusted Exposure Concentration
When evaluating carcinogenic risks from exposures that last less than a lifetime, the ADD or
exposure concentration is adjusted to a dose or concentration that would yield an equivalent
exposure if exposure continued for the entire lifetime.
For oral or dermal exposures, this yields the Lifetime Average Daily Dose (LADD):
LADD = ADD * (exposure period in years / lifetime in years)
For inhalation exposures, this yields the Adjusted Concentration:
Adjusted Concentration = Concentration * (exposure period / lifetime)
Typically (and in RISK*ASSISTANT), the adjusted concentration will also incorporate
adjustments for differences between the actual exposure pattern and the assumed pattern of
continuous lifetime exposure. For example, if exposure only occurred for one hour each day, the
Adjusted Concentration would be only l/24th of the concentration during that hour.
LADD
=Lifetime Average Daily Dose.
Units are milligrams of contaminant per kilogram of body weight per day.
Adj.Inh.Conc =Adjusted Inhaled Concentration: Continuous concentration equivalent to
A-3
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exposure concentration; considering frequency and duration of exposure and inhalation rate.
Units are micrograms of contaminant per cubic meter.
Chemical Oral
Medium LADD
Scenario mg/kg/d
18540-29-9 CHROMIUM (VI)
Groundwater
Drinking Water 0.000002
TOTALS 0.000002
Air
Indoor Air
Outdoor Air
TOTALS
Soil
Dust/Soil Indoors 2.3e-007
Dust/Soil Outdoors 2.3e-007
TOTALS 4.7e-007
Inhalation
Adj.Concentration
ug/cu m
0.000306
0.000103
0.000409
0.000004
0.000002
0.000006
Dermal
LADD
mg/kg/d
NOTE: scientific notation is used for numbers less that 0.000001 and greater than 1000000.
For example:0.00000021 = 2.1e-7 = 2.1 / 10000000 and 21000000 = 2.1e7 = 2.1 * 10000000.
ADD/LADD values are meaningful up to the second significant digit.
Carcinogenic Risk
For chemicals that may cause cancer if ingested, risk is calculated as a function of oral Slope
Factor and Dose:
-(Oral Slope Factor * Lifetime Average Daily Dose)
Risk = 1
If the risk results from breathing the chemical,
than dose, as follows:
the calculation is based on concentration, rather
-(Unit Risk * Concentration)
Risk = 1
For dermal exposures, the dose absorbed through the skin is used in combination with the oral slope
factor, using the same equation that is used for calculating risks from oral exposures.
This may lead to underestimation of dermal risk.
These estimates represent theoretical excess cancer risk (i.e. risk over background cancer
incidence) of developing cancer. For example, if the calculated risk is 1 in 1,000,000 (1 e-006),
this would literally suggest that a person would have a one-in-a-million chance of getting cancer
because of the specified chemical exposure, in addition to her/his chance of getting cancer from
other causes.
Oral Slope = Slope of the (carcinogenic) dose-response function,
in the low—dose, linear range.
Used for oral and dermal exposures.
Units are I/(milligram of chemical per kilogram of body weight per day).
Unit Risk = Slope of the (carcinogenic) concentration-response function,
in the low-concentration, linear range.
Used for inhalation exposures.
Units are I/(micrograms of chemical per cubic meter of air).
Slope Factors and Unit Risks are generally estimated as the 95th percentile confidence limits using
the linearized multistage model, when based on animal data (estimates derived from studies in humans
often employ mathematical best estimates). As such, they are conservative estimates of toxic hazard.
Risks estimated by combining these hazard values with exposure estimates are commonly referred to as
upper-bound risks, but because exposure estimates may not represent upper-bound estimates, risk
estimates are not true upper-bound risks.
Weight of Evidence
A
Bl
B2
C
D
E
Chemical
Medium
Scenario
18540-29-9 CHROMIUM (VI)
Weight of Evidence: A
Groundwater
Drinking Water
MEDIUM TOTALS
= EPA class designating overall strength of evidence that
a substance causes cancer in humans.
= Known human carcinogen.
= Probable human carcinogen, limited human data.
= Probable human carcinogen, inadequate or no human data.
= Possible human carcinogen.
= Not classifiable as human carcinogen.
= Evidence that not carcinogenic in humans.
Risk (Odds): Individual Probability of Getting Cancer
from this Exposure Alone
Inhalation Dermal
Oral
No Slope
Missing Slope
Unit Riskd/(ug/m3) ) :0.012 Source: IRIS & HEAST ( 04/14/ 97&04/14/ 97 )
A-4
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Mr
Indoor Air
Outdoor Air
MEDIUM TOTALS
Soil
Dust/Soil Indoors Missing Slope
Dust/Soil Outdoors Missing Slope
MEDIUM TOTALS
ALL MEDIA TOTALS
4 in 1,000,000 (4e-006)
1 in 1,000,000 (le-006)
5 in 1,000,000 (Se-006)
< 1 in 1,000,000 (5e-008)
< 1 in 1,000,000 (3e-008)
< 1 in 1,000,000 (8e-008)
5 in 1,000,000 (5e-006)
NOTE: scientific notation is used for completeness.
For examplerO.00000021 = 2.1e-7 = 2.1 / 10,000,000 (odds of 2 in 10,000,000) and 21,000,000 = 2.1e7 = 2.1
* 10,000,000.
It is generally assumed that carcinogenic risk is zero only when exposure is zero, and that at low
doses, the relationship between dose and response can be approximated by a straight line.
These estimates represent the theoretical excess cancer risk (i.e. risk over background
cancer incidence) of developing cancer. For example, if the calculated risk is 0.000001 (1 e-006),
this would literally suggest that a person would have a one-in-a-million chance of getting cancer
because of the specified chemical exposure, in addition to her/his chance of getting cancer from
other causes. However, in view of the large uncertainties associated with such risk estimates, they
should always be interpreted as general indicators, rather than precise estimates. EPA generally
considers risks below 1 in a 1,000,000 (le-6) to be low.
Hazard Quotient
For agents that cause non-cancer toxic effects, a Hazard Quotient (H.Q.) is calculated, which
compares the expected exposure to the agent to an exposure that is assumed not to be associated with
toxic effects.
For oral or dermal exposures, the Average Daily Dose (ADD) is compared to a Reference Dose (RfD):
H.Q. = Average Daily Dose / Reference Dose
For inhalation exposures, the inhaled concentration is compared to a Reference Concentration (RfC):
H.Q. = Inhaled Concentration / Reference Concentration
An effort is made to ensure that Reference Doses and Reference Concentrations provide a conservative
estimate of non-cancer toxic hazards. The uncertainty factors applied to toxicity data are intended
to take into account differences in sensitivity to toxic effects within and between species, and
differences in toxic effects between chronic and subchronic exposures.
Definitions of abbreviations employed in this table:
RfC
RfD
Chemical
Medium
Scenario
18540-29-9 CHROMIUM
=Reference Concentration (inhaled concentration not associated with toxicity).
Units are milligrams of contaminant per cubic meter of air.
=Reference Dose (daily dose not associated with toxicity).
Units are milligrams of contaminant per kilogram of body weight per day.
Hazard Quotient: Ratio of Average Dose
to 'Safe' Daily Dose
Inhalation Dermal
(VI)
Groundwater
Drinking Water
MEDIUM TOTALS
Air
Indoor Air
Outdoor Air
MEDIUM TOTALS
Soil
Dust/Soil Indoors
Oral
RfD (mg/kg/d): 0.005
0.001096
0.001096
0.000110
Dust/Soil Outdoors 0.000110
No RfC
Missing RfC
Missing RfC
Missing RfC
Missing RfC
Source: IRIS & HEAST(04/14/97&04/14/97)
MEDIUM TOTALS
ALL MEDIA TOTALS
0.000219
0.001315
NOTE: scientific notation is used for completeness.
For example:0.00000021 = 2.1e-7 = 2.1 / 10,000,000 (odds of 2 in 10,000,000) and 21,000,000 = 2.1e7 = 2.1
* 10,000,000.
HQ/HI values are meaningful up to the first significant digit.
It is generally assumed that non-cancer toxic effects have some threshold. That is, up to some
finite level of exposure, physiological defense mechanisms ensure that no toxic effect will occur.
Accordingly, hazard assessment for non-carcinogenic effects involve estimating an exposure that is
less than this threshold level. This is done by applying "uncertainty factors" to exposures that
appear to be near this threshold in laboratory toxicology studies. This yields a Reference Dose
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!RfD) for oral exposures, or a Reference Concentration (RfC) for inhalation exposures.
TOTALS FOR ALL CHEMICALS
Risk (Odds):Individual Probability of
Hazard Quotient Getting Cancer from this Exposure Alone
Oral 0.001315
Inhalation 5 in 1,000,000 (5e-006)
Groundwater 0.001096
Air 5 in 1,000,000 (5e-006)
Soil 0.000219
TOTAL 5 in 1,000,000 (5e-006)
NOTE: scientific notation is used for completeness.
For example:0.00000021 = 2.1e-7 = 2.1 / 10,000,000 (odds of 2 in 10,000,000) and 21,000,000 = 2.1e7 = 2.1
* 10,000,000.
HQ/HI values are meaningful up to the first significant digit.
In some situations, it is appropriate for the user to calculate combined risks from multiple
chemicals and multiple routes of exposure. Many chemicals will produce the same toxic effect,
regardless of the exposure route. For chemicals that cause cancer by several routes of exposure, the
combined risk from all routes may be more informative than route-specific risk estimates, unless
there is evidence that carcinogenic risks from different routes reflect different mechanisms of
action. Similarly, for non-cancer toxic effects, differences between routes may only affect toxic
potency, which will be reflected in the use of route-specific Reference Doses or Reference
Concentrations.
Carcinogenic risk estimates for particular chemicals and routes of exposure may be summed directly
to produce an estimate of total carcinogenic risk. Similarly, Hazard Quotients for chemicals that
produce toxic effects in the same organ system may be summed to yield a Hazard Index. Hazard Indices
< 1.0 are generally considered by EPA to be associated with low risks on non-cancer toxic effects.
In generating estimates of the combined toxic and carcinogenic risks of different chemicals, it is
also important to bear in mind that the risks of exposure to multiple chemicals are not necessarily
additive. Risks may be less than additive, or synergism may lead to risks that are greater than
would be predicted by an additive model. Unfortunately, only very limited data are available on the
risks of exposure to multiple chemicals.
Carcinogenic risks that exceed 0.000001 (1 e-006), whether for a single chemical, route of exposure,
and scenario, or for a combination of chemicals, exposure routes, and scenarios, fall within the
EPA's range of concern. Depending upon the number of persons exposed to these risks and the
plausibility of the assumptions underlying the estimate, some action to control the risks may be
needed. Risks in excess of 0.0001 (1 e -004) are generally considered unacceptable.
In generating estimates of the combined toxic and carcinogenic risks of different chemicals, it is
also important to bear in mind that the risks of exposure to multiple chemicals are not necessarily
additive. Risks may be less than additive, or synergism may lead to risks that are greater than
would be predicted by an additive model. Unfortunately, only very limited data are available on the
risks of exposure to multiple chemicals.
Hazard Quotients and Hazard Indices that exceed 1.0, whether for a single chemical, route of
exposure, and scenario, or for a combination of chemicals, exposure routes, and scenarios, indicate
the possibility of non-cancer toxic risks from the exposure.
If a Hazard Index that exceeds 1.0 represents multiple chemicals and/or multiple routes of exposure,
the assessor should ascertain that exposure to these chemicals/routes will lead to toxic effects in
the same organ system. It may be appropriate to recalculate a Hazard Index that includes only those
chemicals and routes of exposure that have overlapping patterns of toxicity.
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