Pollution from exhaust stacks


Global health experts agree that pollution from traffic exhaust poses serious health risks. Emissions include nitrous oxides and particulate matter that, when breathed into the lungs, causes respiratory diseases such as asthma and emphysema, and cancer. This has been repeatedly proven across numerous independent studies across the world(1).

Medical experts universally state that there is no safe level of exposure to these types of cancer-causing emissions, and that children and the elderly are particularly vulnerable.

Doctors have specifically been concerned with levels of airborne toxins from other similar tunnel projects around Sydney, such as the soon to be completed NorthConnex(2).


Premier Gladys Berejiklian announced in July 2018 that “the proposed ventilation stacks are now away from schools, away from where people live”. Education minister Rob Stokes has said there is “no way in hell he will countenance exhaust stacks being built anywhere near a school”(3).


However the facts are that unfiltered exhaust stacks for this project will be very close to homes and schools, located:

  • on Balgowlah Golf course (within 100m of homes, 500m of schools, child care facilities and aged care)
  • near Kirkwood Ave, Seaforth (within 300m of homes)
  • at Ernest St, Cammeray (within 100m of homes, and 300m of Anzac Park Public School).


It is projected that the exhaust stack at Balgowlah will be visible from the homes of thousands of residents who live on the surrounding hills; from the tall apartments at Stockland Balgowlah, from homes in Ellery Pde Seaforth, Maretimo St Balgowlah and everyone in between.


Watch a video from Dr Ray Nassar explaining the health impacts from exposure to traffic exhaust here: https://vimeo.com/278243564

Exhaust emission dispersal


The science of exhaust emission dispersal from stacks is complex and requires detailed modelling for each precise location – modelling that has not yet been done for these exhaust stack locations. Marketing information from the government tells us that “the exhaust air is indistinguishable from surrounding air”, however the reality is a different story.


Exhaust stack function encompasses the surrounding terrain, heights of nearby buildings and all weather patterns and events. Many factors influence the ability of the concentrated emissions to disperse effectively, including air temperature, exhaust temperature, speed of exhaust expulsion, wind direction and speed.


As with other similar projects in Sydney, pollution will increase for some residents due to air toxins from exhaust stacks, and from increased traffic around the tunnel entrances.


The NSW Chief Scientist report reveals all stack designs involve increased air toxins up to a 1200m radius from an exhaust stack(4). Government documents recently leaked to the media revealed “plume downwash” is also a concern at the site(5), where additional toxins are drawn to ground level.


The Balgowlah exhaust stack is particularly problematic as it is located at a low point in the valley, meaning concentrated exhaust will be distributed over homes and schools on the hills around Balgowlah and Seaforth that overlook the exhaust stack.

The diagram below shows the dispersal of concentrated emissions according to the NSW Chief Scientist report, with the red dots indicating various locations around the Balgowlah stack, including Seaforth Public School, Balgowlah Boys High, Bupa Aged Care Seaforth, Ellery Pde Seaforth and Woodbine St North Balgowlah.


NSW Chief Scientist diagram of plume dispersal


Also within this radius are residences in the wider Seaforth, North Balgowlah, Manly Vale, Fairlight and Balgowlah Heights areas. This demonstrates a wide residential area will be subject to increased pollution due to their proximity to, and height above the exhaust stack.

The problem of “plume downwash” as mentioned in government documents is demonstrated in the diagrams below. It means on certain days and times when temperature inversions or particular sea breezes exist, the concentrated plume of pollution will be drawn even closer to residents’ homes at ground level. These conditions can also lead to concentrated emissions being spread further than the modelled 1200m radius, and again drawn downwards into people’s homes.


Many requests have been made across Sydney for government to filter exhaust stacks, in line with tunnels of similar length in Europe and Asia being filtered. However the NSW government has refused; with the claim that it is inefficient and too costly. To do so would concede filtration reduces air toxins for public health and should be implemented in tunnels all over Sydney – but in the government’s view, it is too expensive and the health benefits are insufficient.


In addition to increased air toxins from exhaust stacks, exposure to vehicle exhaust will increase significantly for residents within a short distance of the tunnel entrance, with increases in traffic travelling to the tunnel, new roads being built and idling traffic queuing at new traffic lights.

But won’t electric cars fix the problem?


Unfortunately, the uptake of electric vehicles will not be the answer. The most dangerous particulates come from diesel exhaust (from a truck fleet that will not be updated to low emission or electric trucks for many decades), and particles that break down from tyres and brakes that will continue to be a problem from all vehicles.

Electric and hydrogen cars bring their own problems; if there is an accident, the batteries are highly flammable and toxic when inhaled. Some countries are even considering banning electric vehicles in tunnels until these risks can be mitigated(6).

The NSW Chief Scientist report on trends in vehicle exhaust emissions states whilst regulatory changes mean new vehicles are cleaner, the increase in roads, number of vehicles and number of kilometres travelled mean total fine particulate matter emissions (from exhausts and tyre wear etc.) plateau and then increase over the next 10-20 years (Page 9)(7).


It is true that air quality overall has been improving in Australia, but as improvements are made and health benefits achieved, why should some in the community suffer airborne toxins significantly higher than others due to their proximity to tunnel exhaust stacks?

1) Air pollution: everything you should know about a public health emergency (The Guardian, November 5, 2018)


2) Doctors fear health impact of NorthConnex tunnel (SMH, September 1, 2014)


3) Exhaust stacks won’t be near schools, says Stokes (Manly Daily, July 19, 2017)


4) NSW Chief Scientist report on Tunnel Air Quality


5) Confidential NSW Government blueprint shows toll-road pollution stacks (ABC News, July 17, 2017)


6) Alternative fuels and the future of road tunnels and road tunnel design


7) NSW Chief Scientist: TP01: Trends in Motor Vehicles and their emissions (November 2018)