OECD Guidelines for the Testing of Chemicals (OECD TG) are a set of internationally accepted specifications for the testing of chemicals decided on by the Organisation for Economic Co-operation and Development (OECD). They were first published in 1981. They are split into five sections:
Section 1: Physical Chemical Properties Section 2: Effects on Biotic Systems Section 3: Environmental Fate and Behaviour Section 4: Health Effects Section 5: Other Test Guidelines
Guidelines are numbered with three digit numbers, the section number being the first number. Sometimes guidelines are suffixed with a letter.
Guidelines are under constant review, with guidelines being periodically updated, new guidelines being adopted, and guidelines being withdrawn. Previous guidelines are maintained on the website for reference purposes. Animal welfare concerns are dealt with by ensuring that animal tests are only permitted where necessary. An OECD Directive obligates a national regulator to use TG studies performed in another member country (Mutual Acceptance of Data, ‘MAD’ (enacting OECD’s mission of reducing non-tariff trade barriers), and the OECD reaches out non-OECD countries to use the TG when those countries regulate chemicals.
Many of the TG for health effects (toxicity tests) function together, in a process called ‘dose-ranging’; lowering doses while extending exposure period. The in vitro effects of a chemical are quickly discovered using a wide range of doses, which sets the doses for acute in vivo tests; next a semi-chronic exposure tests in vertebrates, whose purpose is to find the ‘Maximally Tolerated Dose’ (MTD)–the dose that the animals are likely to tolerate for the duration of the final TG—a chronic test of typically one to two years exposure (to mimic a lifetime of human exposure). The MTD becomes the highest dose in the chronic exposure test, and typically one to three more lower dose levels are added (typically spanning about 20 to 100-fold), often in the ‘mg/kg per day’ range (e.g., 400, 150 & 50 mg/kg d-). See the TG 453 (Combined Chronic Toxicity/Carcinogenicity) for more on dose ranging.
At these high chronic exposure doses, toxicity is likely in some but not all animals, allowing a small, affordable number of animals. The risk assessment is finished by taking the TG's no- or the lowest-effect dose, dividing it by a safety factor (e.g. 100-fold) and comparing that 'safe dose' to the anticipated exposures.
It has been observed that these chronic TG doses are unrealistically high (close to the poisonous doses) for determining effects from our actual exposures–i.e. they do not actually test their hypothesis. Academic researchers in contrast are interested in the hypothesis, ‘what effects from our actual exposures?’, and to date have published at least 20,000 findings of chemicals' toxicity at low doses in vertebrate animals, at the rate of about 3 or 4 every day. The chronic TG have further insensitivities to find toxicity: they sacrifice the animals at the human equivalent of the early sixties of age–before most chronic diseases even manifest. Effects are detected only with visible light microscopes. Finally, they are performed by the party with a huge financial interest in the chemical being shown to be safe enough to market. Nevertheless, regulators, politicians and other stakeholders believe the TG are reliable to determine risks with.
The guidelines are available in both English and French.
List of guidelines
Section 1: Physical Chemical Properties
NumberTitle101 UV-VIS absorption spectra102 Melting point/Melting range103 Boiling point104 Vapour pressure105 Water solubility106 Adsorption – Desorption Using a Batch Equilibrium Method107 Partition coefficient (n-octanol/water): Shake Flask Method108 Complex formation ability in water109 Density of liquids and solids110 Particle size distribution/ fibre length and diameter distributions111 Hydrolysis as a function of pH112 Dissociation constants in water113 Screening test for thermal stability and stability in air114 Viscosity of liquids115 Surface tension of aqueous solutions116 Fat solubility of solid and liquid substances117 Partition coefficient (n-octanol/water), HPLC Method118 Determination of the Number-Average molecular weight and the molecular weight distribution of polymers using Gel Permeation Chromatography119 Determination of the Low Molecular Weight Content of a Polymer Using Gel Permeation Chromatography120 Solution/Extraction Behaviour of Polymers in Water121 Estimation of the adsorption coefficient (KOC) on Soil and on sewage sludge using High Performance Liquid Chromatography (HPLC)122 Determination of pH, Acidity and Alkalinity123 Partition coefficient (1-Octanol/Water): Slow-Stirring Method
Section 2: Effects on Biotic Systems
NumberTitle201 Freshwater Alga and Cyanobacteria, Growth Inhibition Test202 Daphnia sp. Acute Immobilisation Test203 Fish, Acute Toxicity Test204 Fish, Prolonged Toxicity Test: 14-Day Study205 Avian Dietary Toxicity Test206 Avian Reproduction Test207 Earthworm, Acute Toxicity Tests208 Terrestrial Plant Test: Seedling Emergence and Seedling Growth Test209 Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation)210 Fish, Early-life Stage Toxicity Test211 Daphnia magna Reproduction Test212 Fish, Short-term Toxicity Test on Embryo and Sac-Fry Stages213 Honeybees, Acute Oral Toxicity Test214 Honeybees, Acute Contact Toxicity Test215 Fish, Juvenile Growth Test216 Soil Microorganisms: Nitrogen Transformation Test217 Soil Microorganisms: Carbon Transformation Test218 Sediment-Water Chironomid Toxicity Using Spiked Sediment219 Sediment-Water Chironomid Toxicity Using Spiked Water220 Enchytraeid Reproduction Test221 Lemna sp. Growth Inhibition Test222 Earthworm Reproduction Test (Eisenia fetida/Eisenia andrei)223 Avian Acute Oral Toxicity Test224 Determination of the Inhibition of the Activity of Anaerobic Bacteria225 Sediment-Water Lumbriculus Toxicity Test Using Spiked Sediment226 Predatory mite (Hypoaspis (Geolaelaps) aculeifer) reproduction test in soil227 Terrestrial Plant Test: Vegetative Vigour Test228 Determination of Developmental Toxicity of a Test Chemical to Dipteran Dung Flies (Scathophaga stercoraria L. (Scathophagidae), Musca autumnalis De Geer (Muscidae))229 Fish Short Term Reproduction Assay230 21-day Fish Assay231 Amphibian Metamorphosis Assay232 Collembolan Reproduction Test in Soil233 Sediment-Water Chironomid Life-Cycle Toxicity Test Using Spiked Water or Spiked Sediment234 Fish Sexual Development Test235 Chironomus sp., Acute Immobilisation Test236 Fish Embryo Acute Toxicity (FET) Test237 Honey Bee (Apis Mellifera) Larval Toxicity Test, Single Exposure238 Sediment-Free Myriophyllum Spicatum Toxicity Test239 Water-Sediment Myriophyllum Spicatum Toxicity Test240 Medaka Extended One Generation Reproduction Test (MEOGRT)241 The Larval Amphibian Growth and Development Assay (LAGDA)
Section 3: Environmental Fate and Behaviour
NumberTitle301 Ready Biodegradability302A Inherent Biodegradability: Modified SCAS Test302B Inherent Biodegradability: Zahn-Wellens/ EVPA Test302C Inherent Biodegradability: Modified MITI Test (II)303 Simulation Test – Aerobic Sewage Treatment – A: Activated Sludge Units; B: Biofilms304A Inherent Biodegradability in Soil305 Bioaccumulation in Fish: Aqueous and Dietary Exposure306 Biodegradability in Seawater307 Aerobic and Anaerobic Transformation in Soil308 Aerobic and Anaerobic Transformation in Aquatic Sediment Systems309 Aerobic Mineralisation in Surface Water – Simulation Biodegradation Test310 Ready Biodegradability – CO2 in sealed vessels (Headspace Test)311 Anaerobic Biodegradability of Organic Compounds in Digested Sludge: by Measurement of Gas Production312 Leaching in Soil Columns313 Estimation of Emissions from Preservative – Treated Wood to the Environment314 Simulation Tests to Assess the Biodegradability of Chemicals Discharged in Wastewater315 Bioaccumulation in Sediment-dwelling Benthic Oligochaetes316 Phototransformation of Chemicals in Water – Direct Photolysis317 Bioaccumulation in Terrestrial Oligochaetes
Section 4: Health Effects