People living in areas affected by recent gorse fires have been advised to avoid spending prolonged periods of time outdoors.
The HSE offered the advice in a public health statement, after more than 100 gorse fires were detected across the State in recent weeks.
Minister for Agriculture Michael Creed also said on Thursday that people were illegally burning foliage at the moment and this was leading to out-of-control fires.
Landowners and the public were warned this week it is illegal to burn any vegetation growing on land during certain periods.
Anybody found burning vegetation between March 1st and August 31st is liable for prosecution by gardaí.
In its statement, the HSE said people, particularly those in the west of Ireland, should “avoid spending long amounts of time outdoors in areas affected by any smoke or ash.
“Smoke levels will change depending on wind conditions, so please use personal judgment.”
The seriousness of the fires has been attributed to a prolonged dry spell since the beginning of April, with average rainfall at 25 per cent of normal levels for this time of year.
Cloosh Valley in Co Galway has been among the worst affected areas, with one academic saying the smoke pollution arising from the valley's fires had led to air pollution in Galway city comparable to that in Beijing.
Dr Liz Coleman, of the NUI Galway Centre for Climate and Air Pollution Studies, said the city had experienced smoke pollution for two hours on Tuesday, but it dispersed "quite quickly" afterwards.
She told RTÉ that the event was recorded on a monitoring network.
The network’s data, which is webcast live every five minutes, shows smoke pollution reaching at least 20 times the normal background level on Tuesday evening.
High-pollution events can have significant health impacts on sections of the population, including the elderly, immunosuppressed and those with chronic conditions such as asthma, Dr Coleman said.
“All you can do is stay indoors, close the windows and wait for it to pass,” she said.
Dr Coleman said the World Health Organisation had determined that 25 microgrammes of particles per metre cubed is the safest level of air quality. On Tuesday evening in Galway, the reading was 150.
‘Under control’
Meanwhile, Coillte said the fire at Cloosh Valley had been suppressed after fire-fighting on Wednesday.
Vast areas of forest and bog land in the valley have been devastated by the blaze.
Coillte said its staff and Army personnel will remain on site on Thursday to monitor hot spots, “as there is still some risk that fires could reignite”.
“With stable weather conditions and the forecast of rain on Saturday evening, it is hoped that there will be no further resurgence of the fire,” it said.
“A civil helicopter will also remain on standby today should it be needed.”
Donegal Fire Service said it had responded to 51 wild fires over the last five days, but there were currently none burning in the county.
“It is the view of the Donegal Fire Service that the vast majority of these fires are started with some form of human intervention, either accidentally or deliberately, and we would call on all members of the public to be aware of the dangers and consequences of deliberate fire-setting,” said a spokeswoman.
She said some fires “can . . . be started unintentionally by thoughtless and careless behaviour”.
Mr Creed told RTÉ’s Morning Ireland that under the current controlled burning regulations a farmer has to alert the authorities of any planned fires, so they would then be on hand to ensure the blaze did not spread.
He said gorse fires were not without consequences - financially and environmentally - and people should be extremely careful.
