Irish Water has confirmed that one water source in the mid-Leitrim area tested positive for a powerful pesticide in recent weeks.
Glyphosate have been detected in the public drinking water supplies in four different areas of Co Leitrim, including Ballinamore.
The pesticide is mainly for the control of annual broadleaf weeds and grasses and is found in a number of weed killer formulations used by gardeners and growers.
The HSE has confirmed that the levels seen do not represent a threat to public health, but are asking users of pesticides are mindful of best practice when spraying their lands.