​​​​Monitoring requirements

Monitoring methodology

Environmental monitoring of perfluorooctane sulphonate (PFOS) in biota is currently not coordinated in the HELCOM community, but general information about monitoring in the region is documented in the HELCOM Monitoring Manual under the sub-programme: Contaminants in biota.

So far, there are no technical guidelines related to PFOS monitoring in biota in the HELCOM Monitoring Manual and there is a need to develop such common monitoring guidelines.


Current monitoring

Monitoring activities relevant to the indicator, currently carried out by HELCOM Contracting Parties are described in the HELCOM Monitoring Manual in the relevant Monitoring Concept Table.

Sub-programme: Contaminants in biota

Monitoring Concept Table

Denmark, Finland, Germany and Sweden monitor PFOS concentrations in their national monitoring programmes. During the period 2014-2019, Poland will include PFOS analysis in fish muscle to their national monitoring. Germany monitors PFOS in biota from 2018 and in water from 2017. Lithuania monitors PFOS in water, sediments and biota every 3 years since 2015. Estonia will include PFOS analyses in coastal waters (water, sediment and biota) from 2017. The substance is not included in the monitoring programmes in Latvia. No information is available from Russia. A few measurements in water and fish (flounder and herring) were taken from Estonia, Latvia, Lithuania and Poland during the HELCOM SCREEN project (2009). Finland has screening data from several fish species for human consumption along the coast line (Koponen et al. 2015).


Description of optimal monitoring

The core indicator for PFOS requires better geographical coverage in national monitoring programmes and better time series data to enable evaluation of temporal trends. In addition, common HELCOM sampling guidelines would enhance the comparability of results and are currently being developed.

The performance of existing monitoring should be evaluated in relation to the monitoring objectives, but first there is a need to quantify these objectives. These quantitative objectives need to be specified for each kind of monitoring, e.g. temporal trend-, incident-, geographical (spatial)- and compliance monitoring for environmental status and/or human exposure. For example, for temporal trend monitoring: what statistical power is required, during what time period should a certain trend be possible to detect and with what specified power (with certain one-or two-tailed statistical tests at a specified significant level)? With these definitions at hand it is possible to estimate e.g. required sample sizes and sampling frequencies. It can be shown that for a monitoring period of 12 years or shorter, generally the power to detect trends will decrease substantially if the sampling is carried out every second or every third year compared to annual sampling. For geographical studies the required spatial resolution should be determined. For compliance monitoring, it is imperative to know the distance to target levels (and variance) before sample sizes are estimated.

Time series of PFOS concentrations in fish are missing or too short to enable evaluation for several sub-basins in the Baltic Sea region. The geographical resolution is generally too poor to make reliable generalized maps from interpolation of the existing stations using Krieging. No serious attempts to study patterns of variation in fish (coastal- offshore) through variograms have been made that could give guidance to the uncertainty and to the distance between sites needed to achieve required confidence in generalized maps.