Hazard Testing for New Chemical Substances: Regulatory Requirements, Test Items, and Methods

Hazard testing for new chemical substances provides the physicochemical, toxicological, and ecotoxicological data required to register chemicals that are not yet listed on national inventories such as the IECSC, the TSCA Inventory, and the European EC inventory. Performed in accordance with OECD test guidelines and GLP principles at accredited third-party laboratories, these studies underpin environmental management registration under frameworks including China's MEE Order No. 12, EU REACH, and the US Toxic Substances Control Act. This article explains the scope of testing, sample requirements, core test items, analytical methods, and practical considerations for manufacturers and importers.

Technical Overview

A new chemical substance is any chemical that does not appear on the existing chemical inventory of the jurisdiction in which it is manufactured or imported. In China, the key inventory is the Inventory of Existing Chemical Substances of China (IECSC), and substances absent from it are regulated under the Measures for the Environmental Management Registration of New Chemical Substances (Ministry of Ecology and Environment Order No. 12, effective January 1, 2021). Comparable frameworks include EU REACH registration, the Premanufacture Notification (PMN) process under the US Toxic Substances Control Act (TSCA), and K-REACH in South Korea.

Under MEE Order No. 12, registration obligations are tiered by annual tonnage: record filing applies below 1 ton per year, simplified registration applies from 1 to 10 tons per year, and regular registration applies at 10 tons per year or above. Hazard testing generates the scientific evidence needed to classify the substance, screen for persistent, bioaccumulative, and toxic (PBT) or very persistent and very bioaccumulative (vPvB) properties, quantify dose-response relationships, and define the risk control measures attached to a registration certificate.

Hazard evaluation rests on three data pillars: physicochemical properties that govern behavior and classify physical hazards, mammalian toxicity endpoints that characterize health hazards, and ecotoxicological endpoints combined with environmental fate studies that characterize hazards to aquatic and terrestrial ecosystems. The depth of the required dataset scales with tonnage band, exposure scenario, and the outcome of initial screening studies.

Inventory Screening as the First Step

• Confirm the substance identity (CAS number, molecular formula, structural formula, spectral confirmation) before any testing program begins.
• Search the applicable inventories (IECSC, TSCA Inventory, EINECS/ELINCS, Korean and Japanese inventories) to determine whether the substance is actually new.
• Check for applicable exemptions, such as low-volume research and development quantities, articles containing the substance, or intermediates under strictly controlled conditions.

Testing Samples

Pure and Chemically Well-Defined Substances

For mono-constituent and multi-constituent substances, the test sample must be representative of the commercial material intended for registration. Accredited third-party laboratories typically verify identity using infrared spectroscopy, nuclear magnetic resonance, mass spectrometry, and ultraviolet-visible spectroscopy, and document purity, impurity profiles, and water content. A purity of at least 98 percent is generally recommended for toxicology studies, while technical-grade materials may be used when they represent the substance as placed on the market.

Polymers

Polymer assessments emphasize number-average molecular weight and molecular weight distribution, residual monomer and reactant content, the fraction of low-molecular-weight species (typically species below 500 and 1,000 daltons), reactive functional groups, and solubility or extractability in water and environmental media. These parameters determine whether a polymer qualifies for reduced data requirements as a polymer of low concern or whether full testing applies.

UVCB Substances

Substances of unknown or variable composition, complex reaction products, or biological materials require characterization by constituent analysis, chromatographic fingerprinting, and representative sampling protocols. Because batch-to-batch variability affects data interpretation, registrants should harmonize sample selection with the laboratory before initiating studies.

Sample Quantity, Purity, and Logistics

• Physicochemical panels typically require 10 to 100 grams per set of endpoints.
• Aquatic acute toxicity tests on fish, Daphnia, and algae generally consume 100 to 500 grams in total, depending on water solubility and analytical verification needs.
• Mammalian studies such as a 28-day repeated-dose toxicity test may require several hundred grams to more than one kilogram depending on dose levels.
• Samples must be accompanied by a composition certificate, safety data, recommended storage conditions, and stability information to ensure integrity during shipment and the test period.

Testing Items

The test package is assembled from standard hazard endpoints recognized across OECD member jurisdictions. Core items are summarized below.

Physicochemical Properties

• Melting point and boiling point, relative density, and vapor pressure
• Water solubility and partition coefficient (n-octanol/water, log Kow)
• Surface tension, pH, and dissociation constants
• Flash point, flammability, pyrophoricity, and self-heating behavior
• Explosive properties, self-reactivity, and oxidizing properties
• Particle size distribution, including nanoscale characterization where relevant
• Adsorption coefficient (Koc) supporting environmental distribution assessment

Health Hazard Endpoints

• Acute toxicity via oral, dermal, and inhalation routes
• Skin corrosion or irritation and serious eye damage or eye irritation
• Skin sensitization and, where required, respiratory sensitization assessment
• In vitro gene mutation in bacteria (Ames test) and in vitro cytogenicity in mammalian cells (chromosomal aberration or micronucleus)
• Short-term repeated-dose toxicity (28-day) and subchronic toxicity (90-day) studies
• Reproductive and developmental toxicity screening, extended one-generation or two-generation studies at higher tonnage bands
• In vivo mutagenicity confirmation, toxicokinetics, and mechanistic studies triggered by earlier findings

Environmental Hazard Endpoints

• Acute toxicity to fish (96-hour LC50), Daphnia magna (48-hour EC50), and algae (72-hour ErC50 and NOEC)
• Activated sludge respiration inhibition for microbial community effects
• Chronic endpoints at higher tiers: 21-day Daphnia reproduction, fish early-life stage, and fish short-term reproduction tests
• Terrestrial endpoints such as earthworm toxicity, soil microorganism activity, and seedling emergence and growth when exposure indicates a soil risk

Environmental Fate and Degradation

• Ready biodegradability (28-day) as the primary screening study
• Inherent biodegradability and simulation testing in water, sediment, and soil at higher tiers
• Hydrolysis as a function of pH and abiotic phototransformation in water
• Bioaccumulation in fish (BCF) triggered by high log Kow and low degradation rates
• Adsorption-desorption screening using the HPLC method or batch equilibrium method

Testing Methods

OECD Test Guidelines

OECD test guidelines form the internationally harmonized methodological basis. Frequently applied guidelines include OECD TG 102, 103, 104, and 105 for melting point, boiling point, vapor pressure, and water solubility; TG 107 or 117 for the partition coefficient; TG 423, 402, and 403 for acute oral, dermal, and inhalation toxicity; TG 431, 439, 437, and 491 for in vitro skin and eye irritation; TG 429 for skin sensitization (local lymph node assay); TG 471, 473, and 487 for genotoxicity; TG 407 and 408 for repeated-dose toxicity; TG 421, 422, and 443 for reproductive and developmental endpoints; TG 201, 202, 203, 209, 210, and 211 for aquatic toxicity; and TG 301, 302, 305, 308, and 309 for degradation and bioaccumulation.

National and Regional Standard Methods

• Chinese national standards (GB/T series) for chemical hazard testing are largely harmonized with OECD guidelines and are referenced for domestic registration dossiers.
• The US EPA OCSPP 870 series (health effects), 850 series (ecological effects), and 835 series (environmental fate) support TSCA submissions.
• ISO and IEC methods, together with ASTM standards such as ASTM D93 for flash point, cover several physicochemical parameters where OECD guidance does not apply.
• The GB 30000 series provides classification criteria used to assign hazard classes and label elements once test data are available.

GLP Compliance and Laboratory Qualification

Regulatory authorities expect pivotal studies to be conducted under the OECD Principles of Good Laboratory Practice. For registration under MEE Order No. 12, ecotoxicological data must generally be generated by laboratories recognized within China for the relevant endpoints, while physicochemical and certain health-effect data may be accepted from accredited third-party laboratories abroad. ISO/IEC 17025 accreditation further demonstrates analytical competence for supporting measurements such as test concentration verification.

Alternative Approaches and Data Waiving

• Read-across and category approaches using analogue substances with adequate justification
• QSAR predictions, for example with the OECD QSAR Toolbox, for screening endpoints such as log Kow, biodegradation potential, and acute aquatic toxicity
• In vitro and ex vivo methods consistent with the trend toward reducing animal use
• Weight-of-evidence evaluations combining existing literature, industry data, and structurally related substances
• Exposure-based or technical-feasibility waivers, such as waiver of acute inhalation testing for non-volatile, non-inhalable materials

Applications

Regulatory Registration and Notification

Hazard test reports are the technical core of new chemical substance submissions, including record filings, simplified registrations, and regular registrations under MEE Order No. 12, as well as REACH registration dossiers and TSCA PMN files. Complete, GLP-compliant datasets shorten regulatory review cycles and reduce the risk of clarification requests that delay market entry.

Hazard Classification and Chemical Safety Management

Test results feed directly into GHS-based classification under the GB 30000 series, safety data sheet authoring, transport classification, occupational exposure limit proposals, and the design of workplace controls, packaging, and emergency response procedures.

Risk Assessment and Prioritization

Regulators use hazard data together with exposure information to evaluate PBT and vPvB potential, derive predicted no-effect concentrations, and determine registration conditions such as usage restrictions, release limits, and post-registration monitoring obligations.

Research, Development, and Trade Support

Early-stage screening studies allow developers to deprioritize problematic candidates, support intellectual property positioning, and prepare the documentation needed for import customs clearance, downstream user communication, and supply chain audits.

FAQ

What qualifies as a new chemical substance?

A substance is considered new in a given market when it is not listed on that jurisdiction's existing chemical inventory. In China, a substance not found on the IECSC is subject to environmental management registration before manufacture or import above exempted research quantities, regardless of whether it is already registered elsewhere in the world.

Which tests are minimally required at the simplified registration level in China?

For annual volumes of 1 to 10 tons, a baseline package commonly includes key physicochemical properties, acute aquatic toxicity on algae and Daphnia, ready biodegradability, and the Ames test, supplemented by additional endpoints when screening results or structural alerts indicate concern. The exact dataset is confirmed case by case according to the registration route and exposure pattern.

How much sample should be prepared for a full testing program?

A conservative planning figure is 1 to 2 kilograms for a comprehensive physicochemical and ecotoxicological package, with larger reserves required if mammalian repeated-dose studies are included. Laboratories should always be consulted for a precise calculation based on dose levels, solubility, and analytical verification requirements.

How long does hazard testing take?

Physicochemical studies generally complete within 2 to 4 weeks per endpoint, aquatic acute tests within 4 to 8 weeks including culture maintenance, genotoxicity batteries within 1 to 2 months, and a 28-day repeated-dose study within about 3 months. Higher-tier studies such as 90-day toxicity, Daphnia reproduction, or bioaccumulation may extend the timeline to 6 months or more, so a regular registration dataset typically requires 6 to 18 months overall.

Can literature data or computer models replace laboratory testing?

Regulators accept read-across, QSAR estimates, in vitro results, and published data when the justification is scientifically robust and documented, but pivotal endpoints for human health and aquatic toxicity usually require GLP-compliant experimental studies, particularly at higher tonnage bands.

Must all studies be performed in GLP laboratories?

Pivotal studies supporting registration should be conducted under the OECD Principles of Good Laboratory Practice. For China MEE submissions, ecotoxicological data must typically be produced by laboratories recognized domestically, which is why sponsors coordinate study allocation between domestic and overseas facilities early in the project.

Are polymers tested differently from other substances?

Yes. Polymer assessments focus on molecular weight distribution, residual monomers, low-molecular-weight fraction, and extractability. Polymers meeting polymer-of-low-concern criteria benefit from substantially reduced testing, while polymers with high residual monomer content or reactive groups may require a fuller dataset analogous to conventional substances.