Bioaccumulation concept

Table 2 Fate and effects of metals in a stream receiving a point-source of metals (upper part of the table) or diffuse input via urban runoff (lower part of the table). Summary of the expected influence of four different hydrological situations base-flow in a rainy period a flood after a rainy period low-flow after a long period of low rainfall (water scarcity) and a flood produced after this drought. Metal concentration (M) metal retention efficiency (measured on the basis of the nutrient spiraling concept) exposure (dose and duration) bioaccumulation (in fluvial biofilms) and metal sensitivity (of biofihns)...

Binodal curves, 20 320-321 Bins concept, 70 32 Bioaccumulation, of herbicides, 73 310 Bioactive barrier, defined, 3 758t Bioactive fixation, 72 611 Bioactive food ingredients, 7 7 646 Bioactive nutritions, 7 7 645t Bioactive substances identifying, 77 646 safety of, 77 647 Bioactive zone, defined, 3 758t Bioadhesive agents, 9 48, 49 Bioadhesive drug delivery systems, 9 45... 

High school. Teach concepts of toxicology (dose response, etc.) and environmental toxicology (bioaccumulation, etc.), as these concepts can be introduced into general science courses. 

In the previous chapters, various issues of PTS contamination such as magnitude of pollution, environmental transport and fate, features of bioaccumulation in organisms as well as trends of contamination have been discussed with in-depth examples of case studies conducted in particular countries in the Asia-Pacific region. These chapters have provided both general and concrete concept of the ultimate fate of PTS in local perspectives and addressed a number of issues of PTS contamination that specifically exist in each country/area. 

Luoma SN, Rainbow PS. 2005. Why is metal bioaccumulation so variable Biodynamics as a unifying concept. Environ Sci Technol 39 1921-1931. 

REACH introduces the concept of adequate control in EU chemical law. Traditionally, the term adequate control has been used to refer to good practice in the workplace. REACH now redefines adequate control in the form of risk management measures detailed in an exposure scenario necessary for the control of hazardous properties. Through a set of systematic procedures, risk management measures must be selected to reduce exposure below which adverse effects to human health or the environment are likely to occur (i.e., a DNEL, DMEL or PNEC). There is debate as to whether a concept of a safe level of exposure reduction, similar to adequate control, can apply to non-threshold carcinogens and mutagens, endocrine disruptors, persistent, bioaccumulative and toxic (PBT) or VPVB substances (e.g., [270]). Industry may need to demonstrate that exposure to these substances is always avoided or minimised, as specified in Annex I of the REACH Regulation. 

In real life , humans and animals can be exposed to some toxicants both pre- and postnatally. Many organic xenobiotics have the potential to bioaccumulate within exposed individuals, possibly affecting future generations by way of genetic and epigenetic effects. However, reproductive endpoints, such as conception rates and sperm counts, are relatively insensitive, and subtle, toxicant-induced changes in reproductive efficiency can be overlooked or missed (Evans, 2007). 

For inorganic compounds and metals, the concept of degradability as applied to organic compounds has limited or no meaning. Rather the substance may be transformed by normal environmental processes to either increase or decrease the bioavailability of the toxic species. Equally the use of bioaccumulation data should be treated with care. Specific guidance will be provided on how these data for such materials may be used in meeting the requirements of the classification criteria. 

Fig. 1. The concept of attaining an internal effect concentration in time as the result of bioaccumulation. An organism is exposed to a contaminant from the ambient environment, which can be water (top) or soil (middle), or from food (bottom). The more it has taken up the higher its internal concentration will be until a critical internal concentration is reached, e.g. the lethal body burden, and the associated effect, e.g. death, is elicited...

A well-known subacute effect is the growth reduction in algae. Hitherto, only external effect concentrations have been reported for this type of subacute effect, since experimental problems make it difficult to determine those internal effect concentrations, and existing bioaccumulation models for, e. g., fish, do not apply to algae, e.g. [78]. It must be noted that algae and other small organisms are prone to diffusive uptake for contaminants from the ambient environment for which the link between bioconcentration and the internal effect concentration concept would be very promising. 

Numerous relationships exist among the structural characteristics, physicochemical properties, and/or biological qualities of classes of related compounds. Simple examples include bivariate correlations between physicochemical properties such as aqueous solubility and octanol-water partition coefficients (Jtow) and correlations between equilibrium constants of related sets of compounds. Perhaps the best-known attribute relationships to chemists are the correlations between reaction rate constants and equilibrium constants for related reactions commonly known as linear free-energy relationships or LFERs. The LFER concept also leads to the broader concepts of property-activity and structure-activity relationships (PARs and SARs), which seek to predict the environmental fate of related compounds or their bioactivity (bioaccumulation, biodegradation, toxicity) based on correlations with physicochemical properties or structural features of the compounds. Table 1 summarizes the types of attribute relationships that have been used in chemical fate studies and defines some important terms used in these relationships. 

Terrestrial wildlife movements are such that site-specific tools are more efficiently used to refine exposure estimate. In this case, site-specific exposure estimates are used and compared with safe thresholds for toxicity, termed toxicity reference values (TRVs). Toxicity reference values for wildlife have been developed for energetic compounds. This chapter presents a brief overview of the processes used to establish these tools for ERA for explosives and related soil contaminants that are frequently of potential ecological concern at the affected military sites. This chapter also provides recommendations for use of these values in the ERA process. Investigations addressing the importance and extent of habitat disturbance as a component of the ERA process on explosives-contaminated ranges are reviewed in Chapter 11. General bioaccumulation principles and applications of the bioaccumulation factor and bioconcentration factor (BAF and BCF, respectively) concepts that are often employed in the ERA process to determine bioaccumulation potential of MC for terrestrial receptors are reviewed in Chapter 10. 

It is understood that the concept of fugacity can be potentially very useful in identifying the static and dynamic behavior of toxic substances in the environment. Phenomena such as bioaccumulation becomes readily understandable and predictable. Also, it is valuable in assisting in the elucidation of the dominant process responsible for a substance s degradation or removal from the environment, and in identifying the signiHcant transfer process. 

Also, although the concept of a quality objective has a similar meaning for several international organisations, the procedures proposed for the setting of quality objectives can be extremely different. In some cases these procedures are supported by relatively rigid rules such as the USEPA approach (Stephan et al., 1985), which requires 16 acute toxicity tests, 3 chronic tests, 2 plant tests, and 1 bioaccumulation study. The procedures proposed by the OECD and practised, for example, in the Netherlands for assessment of the effects of priority chemicals are very similar in design as well as in their quantifiable details. 

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