How might the Melbourne factory fire affect health and the environment? An air pollution expert explains

A very large factory fire in Melbourne sent plumes of thick, dark smoke billowing across the western part of the city on Wednesday afternoon, with authorities issuing warnings for people in surrounding suburbs. The fire has now been brought under control, but efforts to control the impacts will likely continue for days.

It has been reported the fire, which Fire Rescue Victoria said involved a large chemical explosion, was at a site run by the chemical blending corporation ACB Group.

That’s yet to be officially confirmed at the time of writing, but is consistent with the type of fire seen in media footage. ACB Group mixes together a range of different hazardous chemicals for various industries.

We don’t know at this stage exactly what was on site during the fire. But when I looked at a cached version of the ACB Group’s website on Wednesday afternoon, I could see they handle common flammable compounds such as fuels, corrosive substances, chemicals supplied to the automotive industry and various solvents and thinners. These chemicals are typically highly flammable.

The issue is that when you have so many liquids like these stored together, once a fire starts and you get an explosion, it will continue to grow and burn very intensely.

People reported seeing barrels exploding and launching themselves into the air, which makes it particularly hard to battle the fire.

In a fire with so much fuel, not enough air is available to completely burn those chemicals. This results in the plumes of thick, black, billowing smoke seen here.

Why is smoke from a fire like this a problem?

The first thing to remember is that all smoke is harmful. Typically, if you can smell smoke, it’s at a level where it could be impacting your health.

It’s not so much a function of what produced the smoke from Wednesday’s fire; it’s just there was so much of it and it was so concentrated.

Smoke contains ultrafine particles known as PM2.5 (PM stands for “particulate matter”). There might be other vapours in there specific to the fuel source – but even in the absence of those, smoke has particulate matter in it and that is harmful to health, no matter the chemical composition.

I looked at PM2.5 levels across Melbourne and at the start of Wednesday they were very low. But PM2.5 levels did spike in the west of Melbourne in the afternoon, reaching levels of concern.

Fortunately they have since come back down, but may increase again on Wednesday night as mixing slows down in the still night air.

If you are especially sensitive to particulate matter – for example, if you have asthma or a respiratory condition – and you ever find yourself close to smoke like this, you could do the following things:

• stay indoors or away from affected suburbs

• close ventilation openings

• close windows and doors

• try to isolate yourself in clean air and wait until the air quality has improved outside

• wear an N95 or P2 mask if must go outside.

It’s similar to what you would do in cases where bushfire smoke is affecting air quality.

Across broader Melbourne, though, the air quality threat quickly dissipated.

Longer-term effects

The more lingering environmental effect is the threat to waterways. The risk is the water used to put out the fire carrying chemicals, ash and debris from the fire to local waterways, which can cause problems for plants and animals. Authorities would be actively trying to manage that risk.

For humans, incidents such as these can contribute to the burden of air pollution that people in cities deal with over the long term.

This long-term exposure to poor quality air is now known to contribute to many conditions affecting almost every part of our bodies.