A number of householders in the Murrisk area of Co Mayo have been asked by the Western Health Board to source an alternative supply of water because of the presence of low levels of arsenic in wells recently bored in the area.
The board has stressed that there is no need for alarm and that the public water scheme in the area is not affected. Although further tests have to be carried out, it is believed that the arsenic is occurring naturally. Contamination of water supplies can occur when water percolates through rocks containing arsenic traces.
Letters have been sent by the board to "four or five" householders in the Murrisk area asking them to use alternative water supplies while the situation is further investigated and clarified.
The presence of the arsenic was identified by laboratory experts only last week, and the health board and Mayo County Council have come together to issue explanatory leaflets on the matter.
Dr Declan McKeown, director of public health with the Western Health Board, said low levels of arsenic had been discovered in a number of deep water wells which had been bored in the area.
"All the evidence points to the arsenic coming from natural sources," he said. "There is nothing to suggest that it has come from industrial or pollution sources."
Dr McKeown stressed that there was no cause for alarm, and people on group schemes and with private wells who had not been contacted could go on using the supply as before.
The board has written to a number of householders in the Murrisk area informing them of the findings and requesting water supplies for sampling.
"We're trying to determine that the problem is not more widespread," he said.