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| '''Bioconcentration''' is the accumulation of a chemical in or on an organism when the source of chemical is solely water.<ref name="Tox. II Book">{{cite book|title=Introduction to Environmental Toxicology: Molecular Structures to Ecological Landscapes|year=2011|publisher=CRC Press|location=Boca Raton, FL|isbn=978-1-4398-0410-0|pages=117–162|author=Landis WG, Sofield RM, Yu MH|edition=Fourth}}</ref> Bioconcentration is a term that was created for use in the field of [[aquatic toxicology]].<ref name="Tox. II Book" /> Bioconcentration can also be defined as the process by which a chemical concentration in an aquatic organism exceeds that in water as a result of exposure to a waterborne chemical.<ref name="Gobas and Morrison Book">{{cite book|title=Handbook of Property Estimation Methods for Chemicals: Environmental and Health Sciences|year=2000|publisher=Lewis|location=Boca Raton, FL, USA|author=Gobas FAPC|authorlink=Bioconcentration and bioaccumulation in the aquatic environment|coauthors=Morrison HA|editor=Boethling RS, Mackay D, eds|pages=189–231|chapter=Biococentration and biomagnification in the aquatic environment}}</ref>
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| There are several ways in which to measure and assess [[bioaccumulation]] and bioconcentration. These include: octanol-water [[partition coefficient]]s (K<sub>OW</sub>), bioconcentration factors (BCF), bioaccumulation factors (BAF) and biota-sediment accumulation factor (BSAF). Each of these can be calculated using either [[empirical data]] or measurements as well as from [[mathematical models]].<ref name="Arnot and Gobas (2004)">{{cite journal|last=Arnot|first=Jon A.|coauthors=Frank A.P.C. Gobas|title=A Food Web Bioaccumulation Model for Organic Chemicals in Aquatic Ecosystems|journal=Environmental Toxicology and Chemistry|year=2004|volume=23|issue=10|pages=2343–2355}}</ref> One of these mathematical models is a [[fugacity]]-based BCF model developed by Don Mackay.<ref name="Mackay (1982)-Fugacity">{{cite journal|last=Mackay|first=Don|title=Correlation of bioconcentration factors|journal=Environmental Science and Technology|year=1982|volume=16|pages=274–278}}</ref>
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| Bioconcentration factor can also be expressed as the ratio of the concentration of a [[chemical]] in an [[organism]] to the [[concentration]] of the chemical in the surrounding [[environment (biophysical)|environment]]. The BCF is a measure of the extent of chemical sharing between an organism and the surrounding environment.<ref name="Ecology PBT Definitions">{{cite web|title=Chapter 173-333 WAC Persistent Bioaccumulative Toxins|url=http://www.ecy.wa.gov/laws-rules/wac173333/p0407_cont_a.pdf|work=Department of Ecology|accessdate=6/2/2012}}</ref>
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| In surface water, the BCF is the ratio of a chemical's concentration in an organism to the chemical's aqueous concentration. BCF is often expressed in units of liter per kilogram (ratio of mg of chemical per kg of organism to mg of chemical per liter of water).<ref name="Fate and Transport Book">{{cite book|last=Hemond|first=Harold|title=Chemical Fate and Transport in the Environment|year=2000|publisher=Elsevier|location=San Diego, CA|isbn=978-0-12-340275-2|pages=156–157}}</ref> BCF can simply be an observed ratio, or it can be the prediction of a partitioning model.<ref name="Fate and Transport Book" /> A partitioning model is based on assumptions that chemicals partition between water and aquatic organisms as well as the idea that chemical equilibrium exists between the organisms and the aquatic environment in which it is found<ref name="Fate and Transport Book" />
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| == Calculation ==
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| Bioconcentration can be described by a bioconcentration factor (BCF), which is the ratio of the chemical concentration in an organism or biota to the concentration in water:<ref name="Gobas and Morrison Book" />
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| <math>BCF=\frac{Concentration_{Biota}}{Concentration_{Water}}</math><ref name="Gobas and Morrison Book" /> | |
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| Bioconcentration factors can also be related to the octanol-water partition coefficient, K<sub>ow</sub>. The octanol-water [[partition coefficient]] (K<sub>ow</sub>) is correlated with the potential for a chemical to [[bioaccumulate]] in organisms; the BCF can be predicted from log K<sub>ow</sub>, via computer programs based on [[structure activity relationship]] (SAR)<ref name="USEPA PBT Info.">{{cite web|title=Category for Persistent, Bioaccumulative, and Toxic New Chemical Substances|url=http://www.epa.gov/fedrgstr/EPA-TOX/1999/November/Day-04/t28888.htm|work=Federal Register Environmental Documents|publisher=USEPA|accessdate=3 June 2012|author=EPA}}</ref> or through the [[linear equation]]:
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| <math>log BCF=m log K_{OW}+b</math> <ref name="Mussel Study">{{cite journal|last=Bergen|first=Barbara J.|coauthors=William G. Nelson, Richard J. Pruell|title=Bioaccumulation of PCB Congeners by Blue Mussels (''Mytilus edulis'') deployed in New Bedford Harbor, Massachusetts|journal=Environmental Toxicology and Chemistry|year=1993|volume=12|pages=1671–1681}}</ref> | |
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| Where:
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| <math>K_{OW}=\frac{Concentration_{octanol}}{Concentration_{water}}=\frac{C_O}{C_W}</math> at equilibrium
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| === Fugacity capacity ===
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| Fugacity and BCF relate to each other in the following equation:
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| <math>Z_{Fish}=\frac{P_{Fish}\times{BCF}}{H}</math> <ref name="Fate and Transport Book" />
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| where Z<sub>Fish</sub> is equal to the [[Fugacity capacity]] of a chemical in the fish, P<sub>Fish</sub> is equal to the density of the fish (mass/length<sup>3</sup>), BCF is the partition coefficient between the fish and the water (length<sup>3</sup>/mass) and H is equal to the Henry's law constant (Length<sup>2</sup>/Time<sup>2</sup>)<ref name="Fate and Transport Book" />
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| === Regression equations for estimations in fish ===
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| {| class="wikitable"
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| ! Equation !! Chemicals Used to obtain equation !! Species Used | |
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| | <math>log BCF=0.76log Kow-0.23</math> || 84 || [[Fathead Minnow]], Bluegill Sunfish, [[Rainbow Trout]], [[Mosquitofish]]
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| | <math>log BCF=log Kow-1.32</math><ref name="Mackay (1982)-Fugacity" /> || 44 || Various
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| | <math>log BCF=2.791-0.564 logS(S=water solubility)</math> || 36 || [[Brook trout]], [[Rainbow trout]], Bluegill Sunfish, [[Fathead minnow]], [[Carp]]
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| | <math>log BCF=3.41-0.508 logS</math><ref name="Chiou et. al">{{cite journal|last=Chiou|first=CT|coauthors=Freed, VH, Schmedding, DW and Kohnert, RL|title=Partition Coefficient and Bioaccumulation of Selected Organic Chemicals|journal=Environmental Science and Technology|year=1977|volume=29|pages=475–478}}</ref> || 7 || Various
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| | <math>log BCF=1.119 log Koc-1.579</math> || 13 || Various
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| |}
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| == Uses ==
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| === Regulatory uses ===
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| Through the use of the [[Persistent bioaccumulative toxic chemical|PBT]] Profiler and using criteria set forth by the [[United States Environmental Protection Agency]] under the [[Toxic Substances Control Act]] (TSCA), a substance is considered to be not bioaccumulative if it has a BCF less than 1000, bioaccumulative if it has a BCF from 1000-5000<ref name="BCF Range">{{cite web|title=Bioaccumulation Criteria|url=http://www.pbtprofiler.net/criteria.asp|accessdate=3 June 2012}}</ref> and very bioaccumulative if it has a BCF greater than 5,000.<ref name="BCF Range" />
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| == Applications ==
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| A bioconcentration factor greater than 1 is indicative of a [[hydrophobic]] or [[lipophilic]] chemical. It is an indicator of how probable a chemical is to [[bioaccumulate]].<ref name="Tox. II Book" /> These chemicals have high lipid affinities and will concentrate in tissues with high lipid content instead of in an aqueous environment like the [[cytosol]]. Models are used to predict chemical partitioning in the environment which in turn allows the prediction of the biological fate of lipophilic chemicals.<ref name="Tox. II Book" />
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| === Equilibrium partitioning models ===
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| Based on an assumed steady state scenario, the fate of a chemical in a system is modeled giving predicted endpoint phases and concentrations.<ref name=Rand>{{cite book|last=Rand|first=Gary|title=Fundamentals of Aquatic Toxicology|year=1995|publisher=CRC Press|location=Boca Raton|isbn=1-56032-091-5|pages=494–495}}</ref>
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| === Fugacity models ===
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| Fugacity is another predictive criterion for equilibrium among phases that has units of pressure. It is equivalent to partial pressure for most environmental purposes. It is the absconding propensity of a material.<ref name="Tox. II Book" /> BCF can be determined from output parameters of a fugacity model and thus used to predict the fraction of chemical immediately interacting with and possibly having an effect on an organism.
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| === Food web models ===
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| If organism-specific [[fugacity]] values are available, it is possible to create a food web model which takes [[Food web|trophic webs]] into consideration.<ref name="Tox. II Book" /> This is especially pertinent for [[conservative chemicals]] that are not easily metabolized into degradation products. [[Biomagnification]] of conservative chemicals such as toxic metals can be harmful to [[apex predators]] like [[killer whales|orca whales]], [[osprey]], and [[bald eagles]].
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| == Applications to toxicology ==
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| === Predictions ===
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| Bioconcentration factors facilitate predicting contamination levels in an organism based on chemical concentration in surrounding water.<ref name=Rand /> BCF in this setting only applies to aquatic organisms. Air breathing organisms do not take up chemicals in the same manner as other aquatic organisms. Fish, for example uptake chemicals via [[ingestion]] and osmotic gradients in [[gill lamellae]].<ref name="Fate and Transport Book" />
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| When working with [[benthic macroinvertebrates]], both water and [[benthic]] sediments may contain chemical that affects the organism. Biota-sediment accumulation factor (BSAF) and [[biomagnification factor]] (BMF) also influence toxicity in aquatic environments.
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| BCF does not explicitly take metabolism into consideration so it needs to be added to models at other points through uptake, elimination or degradation equations for a selected organism.
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| === Body burden ===
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| Chemicals with high BCF values are more lipophilic, and at equilibrium organisms will have greater concentrations of chemical than other phases in the system. Body burden is the total amount of chemical in the body of an organism,<ref name=Rand /> and body burdens will be greater when dealing with a lipophilic chemical.
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| == Biological factors ==
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| In determining the degree at which bioconcentration occurs biological factors have to be kept in mind.The rate at which an organism is exposed through respiratory surfaces and contact with dermal surfaces of the organism, competes against the rate of excretion from an organism. The rate of excretion is a loss of chemical from the respiratory surface, growth dilution, fecal excretion, and [[metabolic biotransformation]].<ref name="Review article of BCF and BAF" /> Growth dilution is not an actual process of excretion but due to the mass of the organism increasing while the contaminant concentration remains constant dilution occurs.
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| The interaction between inputs and outputs is shown here:<br />
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| <math>\frac{dC_{B}}{dt}=(k_{1}C_{WD})-(k_{2}+k_{E}+k_{M}+k_{G})C_{B}</math><ref name="Review article of BCF and BAF" /><br />
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| The variables are defined as:<br />
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| C<sub>B</sub>is the concentration in the organism (g*kg<sup>−1</sup>).<ref name="Review article of BCF and BAF" />
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| t represents a unit of time (d<sup>−1</sup>).<ref name="Review article of BCF and BAF" />
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| k<sub>1</sub> is the rate constant for chemical uptake from water at the respiratory surface (L*kg<sup>−1</sup>*d<sup>−1</sup>).<ref name="Review article of BCF and BAF" />
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| C<sub>WD</sub> is the chemical concentration dissolved in water (g*L<sup>−1</sup>).<ref name="Review article of BCF and BAF" />
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| k<sub>2</sub>,k<sub>E</sub>,k<sub>G</sub>,k<sub>B</sub> are rate constants that represent excretion from the organism from the respiratory surface, fecal excretion, metabolic transformation, and growth dilution (d<sup>−1</sup>).<ref name="Review article of BCF and BAF" />
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| Static variables influence BCF as well. Because organisms are modeled as bags of fat, lipid to water ratio is a factor that needs to be considered.<ref name="Fate and Transport Book" /> Size also plays a role as the surface to volume ratio influence the rate of uptake from the surrounding water.<ref name="Review article of BCF and BAF" /> The species of concern is a primary factor in influencing BCF values due to it determining all of the biological factors that alter a BCF.<ref name="Fate and Transport Book" />
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| == Environmental parameters ==
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| === Temperature ===
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| Temperature may affect metabolic transformation, and bioenergetics. An example of this is the movement of the organism may change as well as rates of excretion.<ref name="Review article of BCF and BAF" /> If a contaminant is ionic, the change in pH that is influenced by a change in temperature may also influence the bioavailability<ref name="Tox. II Book" />
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| === Water quality ===
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| The natural particle content as well as organic carbon content in water can affect the bioavailability. The contaminant can bind to the particles in the water, making uptake more difficult, as well as become ingested by the organism. This ingestion could consist of contaminated particles which would cause the source of contamination to be from more than just water.<ref name="Review article of BCF and BAF">{{cite journal|last=Arnot|first=Jon|coauthors=Frank A.P.C. Gobas|title=A review of bioconcentration factor (BCF) and bioaccumulation factor (BAF) assessments for organic chemicals in aquatic organisms|journal=NRC Canada|date=13 December 2006|volume=12|pages=257–297|doi=10.1139/A06-005|url=http://research.rem.sfu.ca/papers/gobas/A%20Review%20of%20Bioconcentration%20factor%20(BCF)%20and.pdf|accessdate=7 June 2012}}</ref>
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| ==References==
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| {{Reflist}}
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| ==External links==
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| * [http://www.pbtprofiler.net PBT Profiler]
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| * [http://faculty.wwu.edu/harperr3/ Ruth "The Hammer" Sofield]
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| * [http://chm.pops.int/Convention/ThePOPs/tabid/673/Default.aspx Persistent Organic Pollutants]
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| * [http://www.epa.gov/ United States Environmental Protection Agency]
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| {{Commons category|Toxicology}}
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| {{Commons category|Ecotoxicology}}
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| {{Toxicology}}
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| <br />
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| {{DEFAULTSORT:Bioconcentration Factor}}
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| [[Category:Toxicology]]
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| [[Category:Environmental science]]
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| [[Category:Aquatic ecology]]
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| [[Category:Chemistry]]
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| [[Category:Environmental toxicology]]
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