Title 22 Hazardous Waste Bioassay
- joe15219
- Apr 25
- 2 min read
Updated: Apr 25
The Title 22 Hazardous Waste Bioassay is a regulatory biological test defined by California Code of Regulations (CCR), Title 22, Division 4.5. It is designed to assess whether a waste exhibits the characteristic of acute aquatic toxicity, one of several criteria used to determine whether a waste is classified as hazardous in California.
Title 22 Hazardous Waste Bioassay
Under Title 22, Chapter 11, Article 3, a waste is deemed hazardous if it exhibits certain characteristics, including toxicity. One type of toxicity defined under these regulations is acute aquatic toxicity, which is evaluated using bioassays that expose aquatic organisms to the waste material or its extract.
The standard Title 22 bioassay is a 96-hour acute aquatic toxicity test. It is typically conducted using freshwater species such as the fathead minnow (Pimephales promelas) or rainbow trout (Oncorhynchus mykiss), although other species may be approved. The organisms are exposed to various concentrations of the waste or leachate in a controlled environment, and their survival is monitored over a 96-hour period.
The primary goal is to determine the LC50 (lethal concentration 50%), which is the concentration at which 50% of the test organisms die within the 96-hour period. According to Title 22, if the LC50 is ≤ 500 mg/L, the waste is considered to exhibit acute aquatic toxicity and is therefore classified as hazardous. The test is conducted under strict laboratory conditions, following protocols established by the California Department of Toxic Substances Control (DTSC) and based on methodologies developed by organizations like the U.S. EPA and ASTM.
The sample tested can be either the neat waste or an aqueous extract, depending on the physical and chemical nature of the waste. For example, solid wastes are often tested using a water leachate prepared by a standardized extraction method.
In practice, this bioassay is a tool for:
Hazardous waste classification: Industries and waste generators use it to determine whether their waste streams require management as hazardous under California law.
Regulatory compliance: It ensures that businesses comply with state-level hazardous waste management laws, which are more stringent than federal regulations under RCRA (Resource Conservation and Recovery Act).
Environmental risk assessment: The bioassay provides insight into the potential harm a waste might cause to aquatic ecosystems if improperly disposed.
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