Ecological risk assessment is the process by
which exposure and effects data are systematically evaluated to
assess the likelihood that adverse ecological effects may occur as a
result of exposure to stressors. In California, technical data needs
for ecological risk assessment are diverse and include both chemical-
and species-specific exposure and effects information. These data
needs are often met by data retrieval from the scientific literature
or by collection of new data. In order to facilitate access to
existing information that may be utilized in ecological risk
assessments conducted or reviewed by member boards, departments, and
offices within the California Environmental Protection Agency
(Cal/EPA), the Office of Environmental Health Hazard Assessment
(OEHHA), in collaboration with the University of California at Davis,
Information Center for the Environment, has developed Cal/Ecotox.
Cal/Ecotox is a relational database which contains California Wildlife Biology, Exposure Factor,
and toxicity information.
The database collates species-specific information for 28 exposure
factors (e.g., body weights, ingestion rates, seasonal activities and
population dynamics) commonly used to estimate exposure to
contaminants. The exposure factors in Cal/Ecotox were patterned
after the United States Environmental Protection Agency (USEPA)
Wildlife Exposure Factor Handbook (USEPA, 1993) but augment USEPA's
efforts by including information for 62 California mammal, bird,
reptile and amphibian species. In addition to exposure factors,
toxicological data for population-level to individual-level effects
have been included for these species, when available.
Cal/Ecotox is a unique database in that it combines exposure and
effects information for a wide variety of California terrestrial
species. It will continue to expand as data for additional
terrestrial, and eventually aquatic, species are added and as data
for the current species are updated. By providing convenient access
to this scientific information, it is hoped that regulators, the
regulated community and the public may benefit due to the improved
quality of ecological risk assessments that are produced using Cal/Ecotox.
Content of Cal/Ecotox
Literature searches were conducted to
identify available exposure factor and toxicological information for
each wildlife species in Cal/Ecotox. Relevant data from the primary
literature were entered into Cal/Ecotox as datasets. Each dataset
contains value(s) for the particular exposure factor or toxicological
endpoint, along with a set of dataset descriptors that provide
additional information about the study design. Linked to each dataset
is the citation information to identify the primary literature
source. Additional information about the content of Cal/Ecotox is
Species in Cal/Ecotox
Species coverage in Cal/Ecotox focuses
exclusively on those known to occur in California. Most common
California species also occur outside of the state, and data from
studies conducted in other states may be included in the database,
depending on the availability of California-specific information.
Currently, Cal/Ecotox includes only vertebrate species, and, since a
number of aquatic toxicity databases exist already, the focus of the
initial phase of data entry was on terrestrial or semi-terrestrial
organisms. Ongoing updates of the database are anticipated to include
aquatic taxa and other terrestrial species.
Many of the wildlife species covered by Cal/Ecotox were
selected based on the potential utility of the species to serve as an
indicator or surrogate species in ecological risk assessments. These
species were judged to be potentially useful as representative
species for modeling or extrapolating effects for other species based
on four specific criteria: 1) distribution and occurrence, 2) habitat
type, 3) trophic level and 4) taxonomic group.
Accordingly, the initial group of species entered into Cal/Ecotox
contains common California species that represent a breadth of
taxonomic families, trophic groupings, habitats, and distribution
within the state. An important source of range and habitat
information for species selection was the California Department of
Fish and Game "California’s Wildlife" series (Zeiner et
al., 1988; 1990a; 1990b). Several of the species selected have been
previously reviewed for exposure factors in the Wildlife Exposure
Factors Handbook (USEPA, 1993), and were included for comparative
purposes with respect to USEPA and Cal/Ecotox databases. These
species were also selected because they were associated with large
datasets of existing exposure factor and/or toxicological
information, which permitted testing of Cal/Ecotox querying
capabilities. Other "California" species covered in the
Wildlife Exposure Factors Handbook were specifically not included to
avoid duplication of effort. It is anticipated that this preliminary
list will provide information for a number of appropriate indicator
and/or surrogate species for ecological risk assessment. Use of the
data for surrogate species development, however, would require
incorporation of appropriate species extrapolation methods by the
Additionally, some species covered by Cal/Ecotox were selected
based on their status as a legally rare species requiring special or
priority consideration in ecological risk assessments in California.
These special status species were included on the initial species
list because they are often the target species of ecological risk
assessments, and because identification and recovery of data for
these species can be difficult. As with common species, it was not
practical to include all special status species, and subjective
selection criteria were developed primarily based on type of
protected status. Highest priority in the initial selection of
special status species was given to federally endangered species,
followed by state endangered, federally threatened, and state
threatened species. Several California Species of Special Concern
were also included in this list.
View list of species in Cal/Ecotox
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Literature Sources for Cal/Ecotox
Biological, exposure factor,
and toxicological information in Cal/Ecotox was obtained from
scientific articles in peer-reviewed journals, theses or government
reports. In order to identify these sources of data, extensive
literature searches have been conducted for each species. The searches
follow a two-tiered approach which consisted of electronic database
searches for more recent articles, and reviews of primary and
secondary sources for older articles. Once citations are identified,
a standard procedure is followed to identify, document and retrieve
citations with potentially useful information. Literature searches
for the current version of Cal/Ecotox were completed in February
In order to complete comprehensive searches regarding biological and toxicological data for each species, citations
are gathered from one or more of the following databases:
Aquatic Sciences and Fisheries Abstracts, produced by
Cambridge Scientific Abstracts, contains aquatic science citation
information from journals, conference proceedings and gray
Biosis Preview, a Biological Abstracts, Inc. database,
contains citations from Biological Abstracts which scans 7,500
journals reporting original research and Biological
Abstracts/Reports, Reviews, and Meetings which indexes research
reports, reviews, conference reports, monographs and books.
Current Contents, from the Institute for Scientific
Information, provides citations from over 7,000 journals and meeting
abstracts in the sciences, social sciences, arts and humanities.
Environmental Science and Pollution,
produced by Cambridge Scientific Abstracts, covers aquatic
pollution, ecology, environmental impact statements, and risk
Medline, a part of the National Library of Medicine’s
electronic citations database, covers approximately 4,000 medical
and health sciences journals.
Toxline, produced by Cambridge
Scientific Abstracts, offers access to information in all areas of
toxicology, including chemicals and pharmaceuticals, pesticides,
environmental pollutants, mutagens and teratogens.
Zoological Record, produced by Biological Abstracts, Inc.,
covers references from 6,500 journals, reviews, monographs, meeting
proceedings, books and reports in the field of zoology.
These databases were searched for each species (with the exception
of Aquatic Sciences and Fisheries Abstracts, which was used for
selected species only) to identify citations containing either the
common or scientific (genus and species) species name in the title,
subject or abstract fields.
For each species, the literature cited in reviewed citations was
examined to identify additional sources of data. Additionally, a
number of secondary sources were examined to identify older
citations. A list of the most commonly used secondary sources is
presented in the References section below.
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Biological and Exposure Factors
Biological exposure factors include a variety
of physiological and ecological parameters that are used in
ecological risk assessments for calculating or predicting the
exposure of animals to chemical toxicants. Selection of exposure
factors to include in Cal/Ecotox was largely based on the Wildlife
Exposure Factors Handbook (USEPA, 1993). Unlike the latter document,
however, Cal/Ecotox does not provide estimates, via allometric
equations, of exposure factors for selected species. Only
species-specific empirical data captured from the literature are
included in Cal/Ecotox. Parameters for which no information has been
published remain as data gaps for a given species. A list of the
different exposure factors included in the database is provided
Age at Fledging, Metamorphosis, or Weaning: Age at which
young: 1) can maintain sustained flight (fledging); 2) commence the
process of metamorphosis (metamorphosis); or 3) begin to leave the
nest or den to actively feed for most of their food (weaning).
Age at Sexual Maturity: Earliest age at which first
successful reproduction occurs.
Body Fat: Amount of fat on an animal’s body, often
expressed as a term relative to total body mass (e.g., percent body
Body Weight: Whole body weight, measured as fresh or wet
weight. Body length is also used as an indicator of size.
Clutch or Litter Size: The number of eggs laid per female in
a single nest or clutch, or the number of live offspring born at one
time to one female.
Clutches / Litters per year: Number of clutches or litters
produced per year per female.
Dietary Composition: Food types comprising the diet, often
expressed in terms of relative contribution to the total diet.
Duration of Incubation or Gestation: Incubation is the period
measured from the first day of incubation to the time of the first
egg hatching (birds), or from the laying of the last egg to hatching
(reptiles and amphibians). Gestation is measured as days of active
Fledging Rate or Weaning Rate: Fledging rate is the number of
young fledged per active or successful nest. Weaning rate is the
proportion of young born that leave the nest or den to actively
Food Ingestion Rate: Daily food mass or caloric intake, often
normalized to body weight (g/g-day).
Foraging Distance: Distance or area covered by an individual
for foraging purposes.
Growth Rate: Size (mass or other measure) increase per day
over a specified interval. Can be expressed as a constant associated
with a specific mathematical model.
Hatching Success: Number of eggs hatched per number of eggs
Home Range: Area occupied by an individual or family group on
a daily basis.
Inhalation Rate: The daily total volume of air inhaled or
number of inhalations per unit time.
Longevity: Longevity of adult member(s) of the population.
Maximum longevity is usually measured in studies of captive or
Metabolic Rate: Measured or estimated rate of energy
expenditure (e.g., kcal/kg-day or liters O2/kg-day),
often associated with either basal or free-living conditions.
Population Density: Number of individuals per unit area.
Surface Area: Surface area of an organism reported as total
area or area per unit body weight (cm2 or cm2/g).
Survival/Mortality Rate: Number of individuals in a
population surviving or dying during a specified interval (e.g.,
Territory Size: Size of an area that is occupied by an
individual or family group and is defended against other individuals
of the same species.
Time of Fledging or Metamorphosis: Time(s) of year that young
birds first maintain sustained flight (fledging), or that amphibians
metamorphose or transform from the larval stage to the adult stage
Time of Hatching or Parturition: Time of year that emergence
from eggs (hatching) or birth of young (parturition) takes place.
Time of Mating / Laying: Time of year that mating and/or egg
laying take place.
Time of Migration, Aggregation, or Dispersal: Times of the
year associated with spring and fall migration or annual aggregation
or dispersal movements.
Time of Molt: Time of year that birds and mammals undergo
molt of feathers and fur.
Time of Nesting: Time of year at which general bird nesting
activities occur (inclusive of mating, egg-laying, hatching and
Time of Torpor or Hibernation: Time of winter hibernation or
Water Ingestion Rate: Daily water intake, expressed as mass
of water per unit of body weight (e.g., g/g-day).
Toxicological information in Cal/Ecotox
is intended to assist in the interpretation of exposure information
during the effects assessment and risk characterization phases of an
ecological risk assessment. Included in Cal/Ecotox are
species-specific data relating chemical exposure to effects
(dose-response data) and/or tissue concentrations (bioaccumulation/biotransfer
data). Residue data are included only if there is a link to defined
exposure or effects information. Standardized toxicity tests for
ecological receptors are often not available, such that data
reported in Cal/Ecotox for California species are extremely diverse,
and originate from both field and laboratory studies.
The degree to which toxicological data are available for
different species also varies considerably, with only a few species
having been studied extensively. Toxicity benchmarks or reference
doses for species in Cal/Ecotox are not extrapolated from data
collected from other laboratory species. Since Cal/Ecotox is a
species driven database, complete toxicological profiles for a
particular chemical are not provided. Toxicological data are entered
if they exist for a Cal/Ecotox wildlife species (i.e., a chemical is
covered only when toxicological data for a Cal/Ecotox wildlife
species is available and data for species not covered by Cal/Ecotox,
such a laboratory rats, are not included). Chemicals are listed by
their common, or generic, name (if available) as well as Chemical
Abstracts Service (CAS) Registry number. Additionally, several broad
categories of chemicals, without CAS numbers (e.g., lead compounds,
polycyclic aromatic hydrocarbons), have been added to accommodate
studies where the exact chemical was not identified.
The list of toxicological endpoints used in Cal/Ecotox was
derived from a survey of the wildlife toxicological literature, of
other toxicological databases, and of veterinary and toxicological
texts. In addition to the broad toxicological value types, listed
below, more specific descriptions of the endpoint are included in
Exposure Indicators (TOX-EXP IND)
-Accumulation: Tendency of a chemical to accumulate in the
tissues of an organism via all exposure pathways. Includes chemical
transfer rates, such as that from prey to predator or from parent to
offspring. May be expressed as a factor or ratio, equation, or as
tissue residues corresponding to known exposure levels.
-Biomarkers: Specific or general biological response
(generally at the molecular level) measured in an organism that can
be used to indicate whether and to what degree exposure to a given
chemical has occurred.
-Dose Response Data: Mortality rate in a test population
measured in response to increasing doses (at least three, not
including a control, or zero dose, group).
-Mortality in the Field: Mortality measured in the field
(e.g., carcass searching) associated with defined or undefined
exposure to a chemical(s).
-Toxicity Benchmarks: Mortality expressed as an LD50,
no-observed-adverse-effect level (NOAEL) or
lowest-observed-adverse-effect level (LOAEL).
Non-Reproductive Sublethal (TOX-Non-Repro-Sublethal)
-Behavioral Effects: Includes measures of sensory and motor
function (e.g., spontaneous activity, coordination and strength,
sensory discrimination); natural, innate behaviors (e.g., social and
aggressive behavior, foraging behavior, migratory behavior, etc.);
and cognition, learning and memory (e.g., conditioned avoidance and
preference, recognition abilities, etc.).
-Cellular/Biochemical Effects: Cellular includes measures of
cell organelles and other components, and their associated
functions, production of a particular cell type (e.g., blood cell
counts). Biochemical includes, but is not limited to, measurements of
enzymes (amount or activity of enzymes), immunological molecules,
transport and receptor proteins, hormones (amount or activity),
neurotransmitters, lipids, amino acids, and polysaccharides.
-Genetic Effects: Chromosomal and genome effects (e.g.,
mutations, carcinogenicity, multiple copies, etc.).
-Indirect Effects: Endpoints not associated with direct
exposure to a chemical. Examples include habitat alteration or loss,
change in prey numbers and species, and change in species
-Organ/System Effects: Includes morphological endpoints (form
or structure of a particular organ, or body part) and physiological
endpoints (function of an organism and its parts).
-Whole animal: Parameters that pertain to the whole body of
an animal, including body weight or condition and body temperature.
-Age Distribution Effects: Endpoints associated with the
age/class structure of a population.
-Geographic Distribution Effects: Endpoints associated with
the spatial location of a population.
-Size Effects: Parameters that pertain to the number of
individuals of a defined population (extinction is included here).
-Behavior: Includes male or female adult courtship, nesting
or parental care behaviors, and offspring behavior, where behavioral
change would be due to prenatal exposure.
-Development: Any aspect of prenatal or postnatal development
of offspring. Adverse effects include abnormalities (terata),
changed sex ratios and otherwise altered development and
-Physiology: Any aspect of adult male or female reproductive
physiology, including fertility and other reproductive organ and
-Reproductive Success: Direct measure of reproductive output,
including litter or clutch size (total clutch or litter size of
exposed parents), hatchability (egg-laying species),
fledging/weaning rate, offspring mortality/survival rate, number of
offspring produced over a given period of time (e.g., annual
A number of descriptors are included
for each dataset to provide information on methods used to collect
the data and other study conditions that facilitate interpretation
of the data. Since data quality is not evaluated prior to entry into
Cal/Ecotox, it is anticipated that the user will use such
descriptors to determine whether data quality satisfies his/her
criteria, and whether the data, as collected, are appropriate for
the user’s purposes. In addition, depending on the intended use of
the data, it is strongly suggested that the original citation from
which the data were drawn be reviewed by the user prior to a final
decision regarding use of the data.
Condition of Animal: Refers to modifying factors that may
influence the exposure factor value such as activity, breeding or
Dose-Response Data Format: This is used only if citation
contains toxicological adverse effects data where response was
measured using at least three doses in addition to controls.
"Table" or "Figure" are selected depending on
how the dose-response data are presented in the citation.
Exposure: Includes the value indicating degree of exposure
and units of exposure (includes wet or dry weight designations);
includes frequency of exposures if applicable. May refer to direct
dosing concentrations (eg, feeding of toxicants in the diet) or to
indirect levels of exposure (eg, environmental/media toxicant
concentrations, application rates of toxicants to habitat).
Exposure Duration: Refers to amount of time over which
study animals are subjected to treatments (e.g., internal
exposure, or tissue residues, can continue beyond treatment
period, but this period is not included as part of exposure
Exposure Technique: Refers to the method or route(s) by
which study animals are exposed to the toxicant(s).
Life Cycle Stage:Refers to stage of the animal at
the time the data were collected.
Location – Specific: Refers to the specific location(s)
where the data (field study) or experimental animals (lab study)
Location: Three types of location information may be
selected for each study: 1) County: select California
county(ies) in which a field study was located if reported in
citation; 2) State: select state in U.S. in which field
study was conducted or 3) Laboratory: depending on
conditions under which measurements were made, report that the
study was done in the laboratory.
Sample Size: Refers to the number of animals from which
data were collected to estimate mean or range for exposure factor
value, or for a toxic effect or chemical concentration in tissue.
Season/Month: Refers to time of year in which data were
Sex: Refers to the sex of the animals for which data were
collected (males, females or both).
Specific-Age: Refers to the age of the animal at the time
the data were collected.
Statistical Significance: Refers to whether a change in any
endpoint was statistically different (as indicated in citation)
from controls, pre-treatment measurements, or some other reference
Study Duration: Refers to exposure duration and
post-exposure time over which study animals are observed or
measured for toxicological effects.
Data from citations for the selected species are entered into
Cal/Ecotox if the data adheres to the exposure factor or
toxicological endpoint definitions. No judgment as to data quality
and soundness of the scientific approach used in generating the data
in citations is made. However, quality assurance procedures are followed to ensure that the data entered into Cal/Ecotox accurately
summarized citation data. Data entry personnel are individuals
professionally trained in ecotoxicology and familiar with Cal/Ecotox
data entry procedures. For each step of the data entry process, from
citation review to entry, standard operating procedures (SOPs) are followed in order to make data entry as standardized
and complete as possible. Quality control is also practiced at each
phase of data entry to make sure entered data adhered to the
standards detailed in the SOPs. It is highly recommended
however, that the
original citation be consulted by the database user prior to
applying the information to an ecological risk assessment.
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Catalogue of American Amphibians and Reptiles. Society for the
Study of Amphibians and Reptiles. New York.
Jennings, M.R. and M.P. Hayes. 1994. Amphibian and Reptile
Species of Special Concern in California. California Department of
Fish and Game, Inland Fisheries Division, Rancho Cordova, CA. pp.
Mammalian Species. American Society of Mammalogists. New York (a
Poole, A. and F. Gill (Eds.). The Birds of North America: Life
Histories for the 21st Century. Philadelphia: The Academy of Natural
Sciences; Washington D.C.: The American Ornithologists' Union.
U.S. Environmental Protection Agency (USEPA). 1993. Wildlife
Exposure Factors Handbook. Office of Research and Development,
Washington D.C. EPA/600/R-93/187a & b.
Zeiner, D.C., W.F. Laudenslayer, Jr., K.E. Mayer and M. White
(Eds.) 1988. California's Wildlife, Volume I Amphibians and
Reptiles. State of California, The Resources Agency, Department of
Fish and Game, Sacramento, CA. pp. 272.
Zeiner, D.C., W.F. Laudenslayer, Jr., K.E. Mayer and M. White
(Eds.) 1990a. California's Wildlife, Volume II Birds. State of
California, The Resources Agency, Department of Fish and Game,
Sacramento, CA. pp. 732.
Zeiner, D.C., W.F. Laudenslayer, Jr., K.E. Mayer and M. White
(Eds.) 1990b. California's Wildlife, Volume III Mammals. State of
California, The Resources Agency, Department of Fish and Game,
Sacramento, CA. pp. 407
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