POOR air quality across Melbourne and Geelong may continue to impact Victorians over the weekend.

Stable weather conditions and no wind has meant small particles from urban pollution around both cities has not been blown away.

The Environment Protection Authority (EPA) in a statement on Friday night advised ‘sensitive groups’ may still be at risk following an initial air warning issued earlier.

“Poor air quality currently present over Geelong, Melbourne and the Latrobe Valley could continue across the weekend,” the statement read.

“The poor air quality is caused by stable weather conditions resulting in a build-up of PM2.5 and smoke from activities such as domestic wood heater usage, motor vehicles and other urban sources.

media_camera Still conditions have caused poor air quality in Melbourne and Geelong. Picture: Jake Nowakowski

“… Sensitive groups include people over 65, children 14 years and younger, pregnant women and those with existing heart or lung conditions.

“These people should reduce prolonged or heavy physical activity and, where possible, limit the time spent outdoors.”

The EPA has advised asthma suffers should follow their management plans.

EPA Head of Applied Science Anthony Boxshall said the poor air quality could continue over the weekend.

“It’s really down to the weather,” Dr Boxshall said.

“It’s a beautiful still day out there — but it’s retaining the pollution, we might be stuck with it for a couple of days.”

media_camera Blue skies in Melbourne on the morning commute. Picture: Nicole Garmston

He said the pollution was caused by combustion from factories, homes, cars and trucks — all the things that make our cities tick.

“We’re lucky in Melbourne that our air quality is usually good or fair — but it’s this weather system that is causing it all,” he said.

He warned vulnerable groups to take care and limit their activity while the air quality was poor and steer clear of running a marathon or going for a 10km cycle.

Senior forecaster Peter Newham said air quality wasn’t something the Bureau of Meteorology usually forecast, but despite winds increasing on Friday it could be a few days until the pollution clears.

Poor air quality is expected in Melbourne and Geelong today. If you're sensitive to smoke, stay safe with these tips https://t.co/euaDcmFBLc pic.twitter.com/J5BNpCHXyz — Better Health (@BetterHealthGov) May 12, 2017

“There’s no really strong system to blow away the pollution for a few days yet,” he said.

“It’s difficult to forecast.”

The “PM2.5 particles”, often described as fine particles, are up to 30 times smaller than the width of a human hair.

In Victoria in November nine people died and thousands were hospitalised due to the world’s worst recorded thunderstorm asthma event.

But Dr Boxshall said today’s conditions are completely different to thunderstorm asthma.

People with asthma have been told to follow their asthma management plan.

melissa.meehan@news.com.au

@melissameehanau