The state government says the east-west link's ventilation will improve air quality.
Petrol sales in Victoria are predicted to soar 34 per cent within a decade, according to the state environment regulator.
The Environment Protection Authority says the surge will be driven by an extra 1 million motor vehicles in Victoria by 2022, when the total number is expected to top 5 million.
We're building suburbs four or five kilometres from the nearest public transport...In outer suburbs, some of these houses have four or five cars because of adult children living at home who can't get around any other way.
Motor vehicles are responsible for as much as 70 per cent of the state's total air pollution, the EPA says.
This petrol pollution and Melbourne's reliance on cars have sparked fierce debate around the state government's transport infrastructure priorities.
Proponents of the planned east-west tunnel say it will ease congestion and cater for a growing commuter population.
On the other hand, critics argue that the multibillion-dollar investment would be better spent improving public transport.
Victorian Greens leader Greg Barber said the east-west link would increase vehicle dependency and cancer-causing pollution.
''If they are going to get anything like the 100,000 cars they are claiming will use the east-west road tunnel, that could only come from significant extra vehicle movement to the inner city,'' he said.
''There will be long-term chronic effects that older people, younger people and people with respiratory illness will experience from living in a city with lots of cars and trucks.''
The director of Melbourne University's lung health centre, Gary Anderson, said the government had so far brought in positive reforms to reduce petrol pollution, but warned they would not be enough. ''The issue now is the huge number of cars,'' he said. He was particularly concerned about older diesel engines emitting fine particles that can damage the heart and lungs.
The state government says the east-west link's ventilation will ensure emissions meet air quality standards.
''Not building the east-west link, and instead leaving tens of thousands of cars idling in long queues at the end of the Eastern Freeway, would be a terrible outcome for the environment,'' a government spokeswoman said.
''The current stop-start traffic and congestion along Alexandra Parade and Princes Street likely creates more air quality issues than we would expect from a ventilation structure.''
An RMIT planning expert, Michael Buxton, said the projected increase of 1 million vehicles was due to car dependency in poorly planned outer urban areas.
''We're building suburbs four or five kilometres from the nearest public transport,'' he said.
''People have no option but to drive long distances to work, to shop, to drop kids off at school, to do anything.
''In outer suburbs, some of these houses have four or five cars because of adult children living at home who can't get around any other way.''
Professor Buxton said infrastructure projects, including the east-west link, extending the outer ring road and dispersing freight and logistics centres across the city were all ''major drivers'' of the vehicle increase.
The RACV's vehicle engineering manager, Michael Case, said tighter emissions regulations would help remove ''grossly polluting'' vehicles from the roads.