Biological effect, toxicity measurement

It is assumed that the measurement endpoints for biological effects (toxicity tests, benthic community structure) are appropriate relative to the assessment endpoints. 

Correlations between measured COPCs and biological effects (toxicity, alterations to the benthic community) could be strongly influenced by the presence of unmeasured toxicants that may or may not vary with the measured contaminants. 

It determines the exposure of biota to a potential toxicant initially discharged into the aqueous phase (Section 3.2) and the extent to which it is justifiable to correlate observed biological effects with measured concentrations of the toxicant. 

Deaths of target organisms associated with intentional pesticide applications to insect-infested crops, weed-choked roadsides, and nematode-laced fields are predictable, desirable, and relatively easy to measure. Likewise, catastropic releases of chlorine from ruptured tank cars or of crude oil from scuttled supertankers may produce a spectrum of biological effects including toxicity. These events are easily associated with exposures to toxic substances and particular environmental circumstances. 

Biological effects measurements - chronic toxicity and mutagenicity tests ... 

If the biological effect of a chemical is related to its dose, there must be a measurable range between concentrations that produce no effect and those that produce the maximum effect. The observation of an effect, whether beneficial or harmful, is complicated by the fact that apparently homogeneous systems are, in fact, heterogeneous. Even an inbred species will exhibit marked differences among individuals in response to chemicals. An effect produced in one individual will not necessarily be repeated in another one. Therefore, any meaningful estimation of the toxic potency of a compound will involve statistical methods of evaluation. 

Levels of chlorobenzene and its metabolites have been measured in blood, urine, and exhaled air however, no studies were located linking any level of chlorobenzene in humans with a biological effect. Levels ranging from 0.05 to 17 ng/L were detected in the blood and 25 to 120 pg/L in the urine of residents living near a former toxic chemical dump, while trace amounts were found in exhaled air (Barkley et al. 1980). 

During exposure to contaminated sediments, test organisms can concentrate chemicals in their tissue and exhibit measurable (sub)lethal effects linked to accumulated substances. In the field of sediment toxicity assessment, it is noteworthy to mention that some studies have been conducted to characterize both exposure and biological effects in parallel. Exposure to contaminants can be gauged by measuring their concentrations in water/sediment and tissue, and effects can be estimated with endpoints such as survival and growth. These studies are important, for example, to detect threshold concentrations at which chemicals begin to exert adverse effects. As such, they can be useful to recommend effective chemical quality standards that will be protective of aquatic life. 

Long, E.R. and Chapman, P.M. (1985) A sediment quality triad measures of sediment contamination, toxicity and infaunal community composition in Puget Sound, Marine Pollution Bulletin 16, 405-415. Long, E.R. and Morgan, L.G. (1990) The potential for biological effects of sediment-sorbed contaminants tested in the National Status and Trends Program, NOAA Technical Memorandum NOS OMA 52, Seattle, WA. 

Toxicity LOE received medium weight, since they measure adverse biological effects on receptor species intended to represent the overall assessment endpoint, and incorporate a measurement of COPC bioavailability. However, toxicity LOE are ranked lower than the benthic community LOE due to the need to extrapolate laboratory results as indicative of field effects. 

Bioassay using a biological system which measures toxic effects of the liquid/aquatic phase of a test material (e.g., porewater, elutriate, leachate) and determines a response (e.g., acute and/or chronic toxicity). See also Solid-phase (toxicity) test. Volume 1(2), Volume 2(9). 

The biological effects of compounds, their responses, or y variables, can be assembled in one of two main ways measured directly by the investigators or collected from literature sources, hi the case of the latter it is important where possible to refer to the original literature. Transcription errors are surprisingly common and often propagate from paper to paper to review. Reviews, naturally, are a particularly attractive source of literature information since they can contain a lot of data in one handy source. Toxicity data sources and common errors encountered in literature data are discussed in detail in Chapter 2. 

It has been claimed by some workers that Li is more readily transported into erythrocytes than is Li and that there are differences in their biological effects (72). It has also been postulated that Li may produce fewer side effects or less toxicity than the naturally occurring isotope mixture (73). Li nuclear magnetic resonance (NMR) spectroscopy in vivo has been used to measure tissue lithium levels in humans noninvasively and with safety. These experiments showed tissue lithium concentrations significantly lower than those in the serum (74). The NMR technique has been used also to distinguish the isotopes in transport studies in red blood cells (75, 76) and in other cell types (77). 

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