United States Prevention, Pesticides EPA712-C-08-014
Environmental Protection And Toxic Substances October 2008
Agency (7101)
&EPA Fate, Transport and
Transformation Test
Guidelines
OPPTS 835.2370
Photodegradation
in Air
• -Jl
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INTRODUCTION
This guideline is one of a series of test guidelines that have been
developed by the Office of Prevention, Pesticides and Toxic Substances
(OPPTS), United States Environmental Protection Agency for use in the testing
of pesticides and toxic substances, and the development of test data to meet the
data requirements of the Agency under the Toxic Substances Control Act (TSCA)
(15 U.S.C. 2601), the Federal Insecticide, Fungicide and Rodenticide Act
(FIFRA) (7 U.S.C. 136, et seq.), and section 408 of the Federal Food, Drug and
Cosmetic (FFDCA) (21 U.S.C. 346a).
OPPTS developed this guideline through a process of harmonization of
the testing guidance and requirements that existed for the Office of Pollution
Prevention and Toxics (OPPT) in Title 40, Chapter I, Subchapter R of the Code
of Federal Regulations (CFR), the Office of Pesticide Programs (OPP) in
publications of the National Technical Information Service (NTIS) and in the
guidelines published by the Organization for Economic Cooperation and
Development (OECD).
For additional information about OPPTS harmonized guidelines and to
access this and other guidelines, please go to http://www.epa.gov/oppts and
select "Test Methods & Guidelines" on the left side menu.
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OPPTS 835.2370 Photodegradation in air
(a) Scope—(1) Applicability. This guideline is intended for use in meeting testing
requirements of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) (7 U.S.C. 136, et
seq.). It describes procedures that, if followed, would result in data that would generally be of
scientific merit for the purposes described in paragraph (b) of this guideline.
(2) Background. The source materials used in developing this OPPTS guideline are OPP
161-4 Data requirements for photodegradation studies in air, OPP 160-4 General test standards,OPP
160-5 Reporting and evaluation of data (Pesticide Assessment Guidelines, Subdivision N -
Chemistry: Environmental Fate, EPA report 540/9-82-021, October 1982).
(b) Purpose. Photodegradation studies in air provide data on photolytic pesticide dissipation
and on the nature and persistence of photoproducts formed from pesticides in the vapor phase in
order to assess the potential for general atmospheric contamination and nontarget risk. Information
from these studies enables the Agency to determine the stability of the pesticide when exposed to
sunlight and to predict the likelihood of the pesticide persisting in the environment, the
photoproducts that are likely to be produced, and their stability when exposed to sunlight.
(c) General considerations—(1) Uses supported by study data. Laboratory
photodegradation studies in the vapor phase support end-use products intended for terrestrial,
greenhouse, forestry, and residential outdoor uses. Such data also support orchard or field vegetable
crop uses that involve potentially significant exposure to workers. Data from such studies also
support each application for registration of a manufacturing-use product which legally could be used
to formulate such an end-use product.
(2) EPA evaluation. The agency will evaluate the following information provided by the
registration applicant to make an assessment of the potential for exposure to pesticides in the vapor
phase:
(i) Vapor pressure at 25 °C and water solubility of the pesticide active ingredient.
(ii) Soil adsorption coefficient (Kd) of the test substance using the soil from a typical
intended application site.
(iii) Soil characteristics, including moisture content, at the intended site of application.
(iv) Method, rate, and intervals of pesticide application.
(v) Temperature, humidity, and air flow rates at the site of application.
(vi) Ventilation sequences or practices for commercial greenhouse applications.
(3) Prior consultation. In view of methodological difficulties with the study of
photodegradation in air, prior consultation with the Agency regarding the protocol is recommended
before the test is performed.
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(d) Test method—(1) Test substance. Studies should be conducted with the technical or
purer grade of each active ingredient in the product, or where radioisotopic analytical techniques are
used (they are preferred), studies should be conducted with the analytical grade of each active
ingredient in the product.
(2) Test procedures—(i) Concentrations. One or more concentrations of the test substance
should be used for this study and at levels that will permit isolation and identification of
photoproducts formed.
(ii) Light sources. Air samples should be exposed to a spectrum of light providing or
simulating expected use conditions. If an artificial light source is used, its intensity, wavelength
distribution, and the length of the exposure should be comparable to sunlight, as the rate of
photolysis is dependent on these factors and will vary if the artificial light source is different from
the natural sunlight.
(iii) Temperature. Temperature should be held relatively constant at 30 °C.
(iv) Controls. Samples of air treated with the pesticide at the same application rates for
irradiated samples and maintained in darkness should be used as experimental controls.
(v) Test duration and sampling intervals. Air samples should be analyzed at four or more
sampling time intervals with at least one observation made after one-half of the test substance has
degraded or 30 days, whichever comes first. The maximum duration of the study does not have to
exceed 30 days.
(vi) Special considerations. Crosby and Moilanen (paragraph (f)(l)) describe use of a
reaction vessel to allow the investigation of vapor phase photolysis while minimizing the effect of
reactions on vessel walls.
(e) Reporting and evaluation of data. Reporting units should be in the metric system.
(1) Test method. Each report should contain a statement regarding the test method used,
including a full description of the experimental design and procedures.
(2) Test substance, (i) The report should identify the test substance, and should include
chemical name of the active ingredient, molecular structure of the active ingredient, and qualitative
and quantitative description of the chemical composition.
(ii) If radiolabeled material is used, the chemical and radiochemical purity of the material, its
activity in Curies/mole and disintegrations per minute per gram (dpm/g) or other standard unit, the
site of radiolabeling, the isotope used, and the source when appropriate.
(iii) Manufacturer, and lot and sample numbers of the test substances.
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(iv) Properties of the test substance, including physical state, pH, and stability.
(3) Light source. If sunlight is used as the light source, a record of the intensity of incident
sunlight, time of exposure, and other major variables which affect incident light such as latitude,
time of year, and atmospheric cover. If artificial light is used as the light source, the nature of the
source, intensity, wavelength distribution, and time of exposure, as well as the relationship of the
light intensity employed to that of natural sunlight should be reported.
(4) Photoproducts. Identification of each photoproduct produced in greater than 10 percent
yield at any point during the course of the study, and material balance and half-life estimates for the
parent substance.
(5) Test equipment. The report should include a description of the test equipment used, and
photographs or detailed descriptions of nonstandard equipment.
(i) The identity of the instrumentation, equipment and reagents used, and the operating
conditions of the instrumentation.
(ii) A description of the equipment used to measure the wavelength range and intensity of
the incident light.
(6) Analytical method. A full description of each method used in this study, the method
validation data, recovery and method detection limit data, quality control procedures and results,
sample chromatograms, sample calculations, and a material balance. A detailed description of the
procedures used in preparation and handling of the sample throughout the method.
(7) Results/discussion. This section should contain the scientific results of the study. Each
report should contain the principal mathematical equations used in generating and analyzing data, as
well as representative calculations using these equations. Data regarding rates of formation and
decline of parent compounds or their degradates should be expressed as amounts, concentrations,
and corresponding percentages. Rate constants should be reported in conjunction with rate data.
Tabular data, as well as graphs for decline curves should be submitted.
(f) References. The following reference should be consulted for additional background
information for developing a protocol to conduct an air photolysis study:
(1) Crosby, D.G., and K.W. Moilanen. 1974. Vapor-phase photodecomposition of
aldrin and dieldrin. Arch. Environ. Contam. Toxicol . 2:62-74.
(2) Reserved.
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