The Mid-Western Health Board last night told residents of Silvermines and Nenagh, Co Tipperary, why blood samples from people in the area were being tested for lead.
An inter-agency group confirmed to a public meeting that human blood testing was continuing in the area.
The group includes the Department of Agriculture and Food in association with the Environmental Protection Agency (EPA), Teagasc, the Mid-Western Health Board, Tipperary (North Riding) Council and the Department of the Marine and Natural Resources.
The chairman of the group, Mr Aidan Murray, said blood was being tested as part of a scientific investigation into the presence and influence of lead in the Silvermines area.
Tests are being carried out on human blood and cattle blood and tissue, as well as soil, water, herbage, silage and dust.
The testing began after a post-mortem on three cattle revealed significant levels of lead in their blood.
The inter-agency investigation is examining an area of about 23 square kilometres, which includes 90 farms, the Silvermines village, and a tailings pond where waste ore and other mining materials were deposited during extensive mining in the region between 1968 and 1982.
Mr Murray said locals had nothing to fear, adding the investigation would provide a clearer picture and indicate measures for residents and relevant agencies to follow.
The Mid-Western Health Board said a drop-in centre would be set up for the blood tests and an information leaflet distributed.
The results of the first tests are due at the end of this week.