The frequency of samples varies from once a month to once a year, depending on the potential impact from industry. However, no such data have been published and the data would probably be of little interest, as most of the municipal treatment plants are no longer in operational or do only mechanical treatment. Moreover, the SAEPF laboratory has just resumed its activities after a long hiatus, but is still limited by tight financial constraints (see chapter 2). Here again, due to lack of financial resources, regular observation has ceased.