Difference between revisions of "Concentrations of PCBs in fish"
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=== Data === | === Data === | ||
| − | Probability distributions of average PCB concentration | + | Probability distributions of '''average WHO-TEQ PCB concentration''' in various fish species were extracted from <ref>http://www.pyrkilo.fi/beneris/index.php/Image:Analytical_data_of_foods-Finland_for_BENERIS_hk_ak.xls</ref> where concentrations of 37 PCB congeners found in marine and freshwater fish samples were collected. Average WHO-TEQ PCB concentration was estimated by the arithmetic mean. Because of small number of measurements per species the non-parametric bootstrap procedure was used to create the probability distribution of the arithmetic mean. |
For fish species with n concentration measurements the procedure employed can be summarized as follows: | For fish species with n concentration measurements the procedure employed can be summarized as follows: | ||
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# Find a parametric probability density function that matches the histogram best. | # Find a parametric probability density function that matches the histogram best. | ||
| − | As a result a set of parametric distributions was obtained that characterize the uncertainty in the average concentration of PCBs in various fish species. | + | As a result a set of parametric distributions was obtained that characterize the uncertainty in the average WHO-TEQ concentration of PCBs in various fish species. |
The parameters of these distributions are summarized below in results part. | The parameters of these distributions are summarized below in results part. | ||
The number of bootstrap replicates m was chosen to be n^n or 2000 (if the numerical evaluation of all n^n samples was impossible). | The number of bootstrap replicates m was chosen to be n^n or 2000 (if the numerical evaluation of all n^n samples was impossible). | ||
| + | |||
| + | |||
| + | |||
| + | The same data and procedure was applied to determine probability distributions of '''average total PCB concentration''' (sum of all PCB congeners) in various sea and inland fish species. The parameters of distributions obtained are given in the result part. | ||
<br> | <br> | ||
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=== Unit === | === Unit === | ||
| − | pg/g fw | + | For '''WHO-TEQ concentration''': pg WHO-TEQ/g fw <br> |
| − | + | For '''total concentration''': ng/g fw <br> | |
| − | |||
| − | |||
| − | <br> | ||
== Result == | == Result == | ||
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|- | |- | ||
| '''Fish species''' | | '''Fish species''' | ||
| − | | ''' | + | | '''Average WHO-TEQ PCB concentration''' |
| + | | '''Total PCB concentration''' | ||
|- | |- | ||
| Baltic Herring | | Baltic Herring | ||
| Normal(2.8797,0.2818) | | Normal(2.8797,0.2818) | ||
| + | | Normal(52.5045,5.8059) | ||
|- | |- | ||
| Vendace(inland) | | Vendace(inland) | ||
| Normal(0.8767,0.1559) | | Normal(0.8767,0.1559) | ||
| + | | Gamma(0.3999,24.1995) | ||
|- | |- | ||
| Vendace(sea) | | Vendace(sea) | ||
| Normal(0.4468,0.0816) | | Normal(0.4468,0.0816) | ||
| + | | Gamma(0.2882,30.0407) | ||
|- | |- | ||
| Whitefish(inland) | | Whitefish(inland) | ||
| Weibull(1.0608,3.8952) | | Weibull(1.0608,3.8952) | ||
| + | | Gamma(0.8863,11.5136) | ||
|- | |- | ||
| Whitefish(sea) | | Whitefish(sea) | ||
| Lognormal(0.7341,0.097) | | Lognormal(0.7341,0.097) | ||
| + | | Lognormal(3.6219,0.1313) | ||
|- | |- | ||
| Pike(inland) | | Pike(inland) | ||
| Gamma(0.1081,5.1975) | | Gamma(0.1081,5.1975) | ||
| + | | Gamma(0.8821,7.6225) | ||
|- | |- | ||
| Pike(sea) | | Pike(sea) | ||
| Normal(1.0544,0.1604) | | Normal(1.0544,0.1604) | ||
| + | | Normal(17.6906,2.8163) | ||
|- | |- | ||
| Perch(inland) | | Perch(inland) | ||
| Beta(7.9494,8.298) | | Beta(7.9494,8.298) | ||
| + | | Gamma(0.3679,14.7802) | ||
|- | |- | ||
| Perch(sea) | | Perch(sea) | ||
| Normal(2.3615,0.3956) | | Normal(2.3615,0.3956) | ||
| + | | Gamma(1.613,24.2709) | ||
|- | |- | ||
| Atlantic Salmon | | Atlantic Salmon | ||
| Normal(11.2524,1.515) | | Normal(11.2524,1.515) | ||
| + | | Normal(194.3885,28.5452) | ||
|- | |- | ||
| Pike-perch(inland) | | Pike-perch(inland) | ||
| Normal(0.6929,0.1551) | | Normal(0.6929,0.1551) | ||
| + | | Normal(10.986,2.4135) | ||
|- | |- | ||
| Pike-perch(sea) | | Pike-perch(sea) | ||
| Normal(1.4828,0.2169) | | Normal(1.4828,0.2169) | ||
| + | | Weibull(29.4135,8.6391) | ||
|} | |} | ||
| − | |||
| − | |||
| − | |||
== References == | == References == | ||
<br> <references /> | <br> <references /> | ||
Latest revision as of 10:24, 7 September 2009
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Scope
Concentrations of PCBs in fish describes average concentrations of polychlorinated biphenyls (PCBs) in fish. Concentrations of marine and freshwater fish species are studied separately.
Definition
Data
Probability distributions of average WHO-TEQ PCB concentration in various fish species were extracted from [1] where concentrations of 37 PCB congeners found in marine and freshwater fish samples were collected. Average WHO-TEQ PCB concentration was estimated by the arithmetic mean. Because of small number of measurements per species the non-parametric bootstrap procedure was used to create the probability distribution of the arithmetic mean. For fish species with n concentration measurements the procedure employed can be summarized as follows:
- Draw m samples of size n with replacement from the original sample. These samples are called bootstrap samples.
- Calculate the sample mean for each of the bootstrap samples.
- Make the density histogram of bootstrap means.
- Find a parametric probability density function that matches the histogram best.
As a result a set of parametric distributions was obtained that characterize the uncertainty in the average WHO-TEQ concentration of PCBs in various fish species. The parameters of these distributions are summarized below in results part.
The number of bootstrap replicates m was chosen to be n^n or 2000 (if the numerical evaluation of all n^n samples was impossible).
The same data and procedure was applied to determine probability distributions of average total PCB concentration (sum of all PCB congeners) in various sea and inland fish species. The parameters of distributions obtained are given in the result part.
Causality
Unit
For WHO-TEQ concentration: pg WHO-TEQ/g fw
For total concentration: ng/g fw
Result
Distributions used: Normal(mean,standard deviation), Beta(alfa,beta), Gamma(alfa,beta), Lognormal(mu,sigma), Weibull(a,b)
| Fish species | Average WHO-TEQ PCB concentration | Total PCB concentration |
| Baltic Herring | Normal(2.8797,0.2818) | Normal(52.5045,5.8059) |
| Vendace(inland) | Normal(0.8767,0.1559) | Gamma(0.3999,24.1995) |
| Vendace(sea) | Normal(0.4468,0.0816) | Gamma(0.2882,30.0407) |
| Whitefish(inland) | Weibull(1.0608,3.8952) | Gamma(0.8863,11.5136) |
| Whitefish(sea) | Lognormal(0.7341,0.097) | Lognormal(3.6219,0.1313) |
| Pike(inland) | Gamma(0.1081,5.1975) | Gamma(0.8821,7.6225) |
| Pike(sea) | Normal(1.0544,0.1604) | Normal(17.6906,2.8163) |
| Perch(inland) | Beta(7.9494,8.298) | Gamma(0.3679,14.7802) |
| Perch(sea) | Normal(2.3615,0.3956) | Gamma(1.613,24.2709) |
| Atlantic Salmon | Normal(11.2524,1.515) | Normal(194.3885,28.5452) |
| Pike-perch(inland) | Normal(0.6929,0.1551) | Normal(10.986,2.4135) |
| Pike-perch(sea) | Normal(1.4828,0.2169) | Weibull(29.4135,8.6391) |
