Roscommon County Council has received several complaints of pollution to rivers caused by illegal dumping recently.
Details released to Shannonside FM also reveal four dead animals were discarded in the countryside in a single month.
Roscommon County Council received a total of 56 environment complaints in May, with 31 relating to litter, 22 to waste and three to water.
A resident told the local authority there were cases of suspected water pollution at the River Lung in Ballaghaderreen and a similar watercourse in Strokestown.
In south Roscommon, a person was allegedly dumping large amounts of grass in a feeder stream for Lecarrow canal and a slurry tank was said to be taking water from a river nearby.
The same month, Leitrim County Council was informed of case of dumping in a river in Carrick-on-Shannon.
Complaints of dumping of dead animals are common in Roscommon and there were four reports in May, involving deer in Athlone and Castlerea, a calf at Moneylube bog in Strokestown and the remains of an animal in a field in Athlone.
Others environment complaints in Roscommon in May included 20 bags of rubbish dumped in Boyle and household furniture discarded at Cloonfad, near Castlerea.
Leitrim council received 12 environment complaints relating to Carrick in May, including an allegation of burying of tyres and burning of waste.