Concentrations of PCBs in fish

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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 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:

1. Draw m samples of size n with replacement from the original sample. These samples are called bootstrap samples.
2. Calculate the sample mean for each of the bootstrap samples.
3. Make the density histogram of bootstrap means.
4. 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.

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)