Water quality in Manx rivers is at a record high with 95% achieving the top rating for chemical levels in 2018, a report has said.
Environment Minister Geoffrey Boot said it was "encouraging" and showed the island "moving in the right direction".
Yet despite the improvement there was a rise in nitrate levels with 46% gaining the highest rating, down from 54%.
Elevated levels of lead were also found in some waterways close to disused mines to the west of the island.
The report was conducted by the Department of Environment, Food and Agriculture (DEFA) and monitored chemical levels in 26 rivers and streams between 2015 and 2018.
Additional monitoring of metal levels, which is not included in the testing method used by DEFA, was undertaken and showed elevated levels of lead in areas of the River Neb and Foxdale Stream closest to the Cross Vein Lead Mines.
Further investigation would be needed to establish the precise source of the contamination, the report said.
The number of rivers achieving the best rating for a low presence of chemicals rose from 88% in 2015.
While the amount of nitrate in the water has increased in some areas it is not at a dangerous level.
Agricultural run-off and private treatment sewage works are potential causes.
Manx Utilities said the company was "pleased" with the results and it was working with DEFA to "support the protection of our river water quality".