The ecologically-sensitive Wadden Sea has become cleaner over the last 30 years thanks to less dumping of manure and phosphates in Dutch rivers, according to a survey published by the Dutch institute for sea research (NIOZ) on Monday.

Reseacher Katja Philippart told ANP that government measures, such as a ban on phosphates in washing powder, have been effective. The Wadden Sea was most polluted in the period between 1985 and 1990, she said.