Bioaccumulation

Bioaccumulation occurs when an organism absorbs a chemical substance at a rate greater than that at which the substance is lost. Thus, even if environmental levels of the substance are very low, the concentration of the substance in living organisms can be much higher. One indicator of whether particular substances will bioaccumulate is the partition coefficient P. 

The partition coefficient is defined as the ratio of the concentration of a substance in the aqueous phase to the concentration of the substance in a water-immiscible solvent (usually n-octanol) as the neutral molecule. Partition coefficients are often quoted as logio values. Thus, a substance with a partition coefficient of 1000 would have a log P value of 3. This latter point on neutrality is very important. 

If the molecule in question contains groups that can act as proton (H ) donors or acceptors, then the neutrality of the molecule will be significantly affected by pH, and thus the pH at which the partihon coefficient must be measured could be anywhere along the pH scale. Since bioaccumulation (which is effectively enhanced partitioning of a substance into the lipid tissues of an organism) will generally only occur for neutral molecules, measurement of the partition coefficient at extreme pH values (which are unlikely to exist in nature) is environmentally irrelevant. 

A more pragmatic study is the determination of the distribution coefficient D. 

This is defined as the ratio between the concentration of the unionized substance in the water-immiscible organic solvent and the concentration of both ionized and unionized substance in the aqueous phase, and this also is usually quoted as its logio value. This value is not a constant but varies with pH. Its advantage is that it can be measured for any pH value (normally around pH 7), which provides an environmentally relevant measure of lipophilicity and thus a clear indication of whether the substance in question is likely to bioaccumulate via partitioning. 

There have been limited studies investigating the bioaccumulation of FSAs and FTOHs (Table 3.2). A study [81] on the uptake, transformation and elimination of FTOHs and PFOS A determined that these compounds are rapidly transformed and eliminated in fish. As such, it is unlikely that most FTOHs and FSAs will undergo substantial bioaccumulation. Furdui et al. [82] have reported a field-based bioaccumulation factor (logBAF) of 3.8 for PFOSA, based on measured concentrations in Great Lakes waters and whole fish homogenates. 

Bioaccumulation studies of PFSAs ( = 6 and 8) and PFCAs ( = 7, 8, 10, 11 and 13) in rainbow trout (Oncorhynchus mykiss) have been conducted by Martin et al. [83, 84] (Table 3.2). These studies indicated that dietary exposure to PFSAs and PFCAs did not result in biomagnification. Bioaccumulation was observed for PFSAs and PFCAs consisting of more than six and seven carbon atoms respectively. The laboratory-based bioconcentration factor (log BCF) for PFOS was 3.04 L/kg and ranged from 0.602 to 4.36 L/kg for the PFCAs. Log BCFs were observed to increase with increasing length of the perfluoroalkyl tail and for the PFCAs increased by a factor of approximately 8 for each additional CF2 moiety for PFCAs ( = 8 to 12), but deviated from linearity for PFTetA. In addition, PFSAs were more bioaccumulative than PFCAs. 

Acetone is highly volatile and readily biodegradable and therefore does not tend to bioaccumulate in the common sense. Therefore, the bioaccumulation of acetone from the environment is scored very low, with very low uncertainty (lA). The tendency of [BMIM] [BF4] and [DMIM] [BFJ to bioaccumulate is unknown. However, [DMIM] [BFJ can be presumed to have a tendency to be incorporated into membranes, because of its stmctural similarity to membrane lipids, comprising a charged head group with a nonpolar tail. Generally, the existing water solubility 

If there is a known adverse effect associated with a chemical, and there is also a potential for widespread exposure, then new information indicating pro-noimced bioaccumulation is reportable. Bioaccumulation in fish beyond five thousand times water concentration, or an n-octanol/water partition coefficient of greater than twenty-five thousand are measures and indications of pronoimced bioaccumulation. 

If an adverse effect that was not previously known is observed in coimection with a chemical that is known to have bioaccumulated to a pronoimced degree or known to be widespread in environmental media, that result must be reported. It is not the fact of bioaccumulation that is reportable under 

The 2006 Frequent Questions include the following parameters describing when data on acute and chronic toxicity in aquatic organisms must be reported  

LC50 is the lethal concentration in 50 percent of organisms, and EC50 is the concentration at which 50 percent of organisms show effects such as those adversely affecting reproductive performance or loss of mobility. 

After exposure to a bioavailable toxicant, absorption takes place and the substance is distributed throughout the body or to the different compartments of the ecosystem. If the substance has high affinity for a certain structure or is lipophilic and slowly metabolized, then bioaccumulation takes place. 

After absorption many xenobiotics enter some kind of depot (e.g. adipose tissue, bone tissue, certain proteins or some other tissue components) and are thus excluded from playing a part in leveling the transport gradients. This means that further absorption will take place and the overall levels of the envirotoxicant in the organisms will increase. 

Source Data derived from G. A. LeBlanc, 1994, Environ. Sci. Technol. 28 154-160. 

Bioaccumulation can lead to a delayed onset of toxicity, since the toxicant may be initially sequestered in lipid deposits but is mobilized to target sites of toxicity 

Biological half-times of cadmium in humans are lengthy. Based on body burden and excretion data, cadmium may remain in the human body for 13-47 years. Although cadmium is excreted primarily in urine and feces, cadmium tends to increase in concentration with age of the organism and eventually acts as a cumulative poison. These phenomena have not been documented adequately in wildlife species. 

Two species of freshwater aquatic mosses (Fontinalis dalecarlica, Platyhypnidium ripa-roides) exposed to concentrations between 0.5 and 6.5 xg Cd/L for 28 days had accumulation factors as high as 137,000 and 158,000, respectively. Accumulations increased with increasing cadmium concentration and decreasing 

The exact mechanism of acute cadmium poisoning is unknown, but, among teleosts, it depends, in part, on exposure period, concentration of dissolved and ionic cadmium in the medium, and water temperature and salinity. Under conditions of high cadmium 

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Formic acid is readily biodegraded, and therefore does not bioaccumulate. The theoretical biological demand (BOD) is 350 mg/g (25). 

Mitex [2385-85-5] is l,2,3,4,5,5,6,7,8,9,10,10-dodecachloro-octahydro-l,3,4-metheno-2JT-cyclobuta-p,<7 -pentalene (37) (mp 485°C). The rat LD s are 306, 600 (oral) and >2000 (dermal) mg/kg. Mirex is extremely resistant to biodegradation and was once considered the perfect stomach poison iasecticide for use ia baits to control imported fire ants. However, even at doses of a few milligrams per 10 m it was found to bioaccumulate ia birds and fish and its registrations were canceled ia the United States ia 1976. 

Citi, Chemicals Inspection and Testing Institute, eds.. Biodegradation and Bioaccumulation Data of Existing Chemicals Based on the CSCE Chemical... 

Exposure of wildlife to EDs also occurs via their food and in most ecosystems there is a tendency for persistent chemicals to bioaccumulate and biomagnify organisms higher up the food chain accumulate more of the chemical than those... 

Tetratchloroethylene has been detected in the food chain as a contaminant its volatility prevents significant bioaccumulation but some transfer to aquatic sediments is possible. At low concentrations it is slowly degraded under anaerobic conditions. 

Upper LEVEL 1 Chronic toxicity Toxicity in soil and plants Additional mutagenicity Long-term toxicity Bioaccumulation Inherent biodegradability Additional abiotic degradability 100 t/annum or 500 t cumulative... 

Bioaccumulation-Accumulation of a chemical substance in living tissue. 

Can the substtmee cause an adverse effect on tlte environment because of its toxicity, persistence, or tendency to bioaccumulate ... 

DOSS, because of its use in foods and pharmaceuticals, was the target of numerous studies concerning toxicity, bioaccumulation, and reproduction as well as gastroenterological issues, so it can be concluded that DOSS is one of the best examined surfactants in the sulfosuccinates. 

Little information on effects of DOSS on marine organisms are available [114-116]. A recently published paper deals with an intensive study of toxicity, bioaccumulation, metabolism, and elimination of DOSS in rainbow trout. The LCjq was determined to be 28 mg/L [116]. A very similar value was found for golden ide [117]. 

Fig. 15-8 The mercury cycle, demonstrating the bioaccumulation of mercury in fish and shellfish. Reprinted with permission from An Assessment of Mercury in the Environment" (1978) by the National Academy of Sciences, National Academy Press, Washington, DC.

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)...

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