The Coastal Resource Coordinator's Bioassessment Manual

HAZMAT 93-1–Toxicity Tests
CHAPTER 3
TOXICITY TESTS
INTRODUCTION
A toxicity test is a procedure that involves the exposure of organisms to complex
environmental samples (water, sediment, or sediment extract) under controlled conditions
to determine if adverse effects occur. Test samples usually contain unknown amounts of
mixtures of contaminants. This procedure is sometimes referred to as a bioassay, but
'toxicity test' is the more appropriate term because a bioassay is a test to determine the
toxicity threshold of a specific substance, while this test is used to determine the toxicity of a
whole sample, not its chemical components. Toxicity tests may be performed in the
laboratory or with caged organisms in the field; however, protocols for in-situ toxicity tests
are still in the developmental stage. Many organisms, from bacteria to mammals, have been
used in such testing, and recently, toxicity tests using cell cultures and biomarker type
indicators have been developed (see Chapter 2). These tests measure a variety of organism
responses (endpoints) to determine the toxic effects of substances on biological organisms.
While the most commonly measured endpoint is death of the organisms, other endpoints
frequently measured include developmental abnormalities, behavioral changes, changes in
reproductive success, and alteration of growth. Although some programs also measure the
bioaccumulation of contaminants at the end of toxicity testing, the use of bioaccumulation
as an endpoint is not discussed in this chapter. Toxicity tests are becoming increasingly
important in bioassessment, in part, because they are relatively inexpensive and numerous
tests can be conducted quickly. Although the following discussion applies to toxicity testing
in general, most of the emphasis is on sediment toxicity tests since these are often
recommended at waste sites.
Objectives of Toxicity Testing
Toxicity tests put environmental chemical data into perspective by acting as a measure of
bioavailability. They can be used to document the extent of bioavailable contamination and
to illustrate the potential for adverse effects at a waste site. Toxicity test results can be used
early in the investigation of a site as a screening tool to indicate whether further
bioassessment (for example, benthic community analyses) should be conducted. Results of
toxicity tests can provide some information to indicate whether (and where) remediation
should occur. Toxicity testing may help determine target levels for remediation. Results of
toxicity tests alone will not be adequate for making remediation decisions; however, when
3-1 August 1997