Simon Birkett, founder of Clean Air London, a campaign group, told EurActiv that local authorities have yet to come up with a convincing plan to tackle the air pollution problems that are expected during the Olympics.
"The Olympic organisers have admitted in March this year that the Olympic route network would cause breaches of air quality laws by displacing traffic and causing congestion," Birkett told EurActiv in a video interview.
"They are working at the moment on designing mitigation measures but we haven't yet seen a package that will tackle that problem," he said.
Birkett was speaking on the sidelines of a EurActiv workshop on air quality, held in October.
Diesel the main culprit
According to the clean air campaigner, the problem is mainly caused by diesel exhausts from cars and trucks.
"Road transport is responsible for about 80% of the most harmful emissions in central and inner London and it is primarily a diesel problem," Birkett said.
Recent government statistics have shown that diesel cars produce 20 times as much pollution as petrol vehicles, he said. "So we really do need to tackle that problem," Birkett stressed.
Emissions of nitrogen dioxide (NO2), which results from the combustion process in vehicle engines, have grown significantly "due to increased penetration of diesel vehicles," according to a recent report by the European Environment Agency (EEA).
Diesel vehicles, it said, can emit "up to 50% of their NOx as NO2," a known toxic gas. "Epidemiological studies have shown that symptoms of bronchitis in asthmatic children increase in association with long-term exposure to NO2," the EEA noted in its report.
And when it comes to NO2, London is bottom of the league. "London has got the worst nitrogen dioxide problem, for example, of any of the 27 capital cities in Europe," said Birkett.
People suffering from allergies and other respiratory diseases will be first affected, warned Susana Palkonen, from the European Federation of Allergy and Airway Diseases Patients Association (EFA). "They are the sort of radars for the quality of the air," she said.
With pollution levels expected to go breach air quality standards, athletes too might experience difficulties, Birkett warned: "If we get high ozone levels as we have had a couple of times this year it really could be an issue for athletes next year."
Mayor to encourage cycling, walking, public transport
The Olympic authorities themselves have admitted that they need to reduce background levels of traffic by 30%, Birkett pointed out.
The London authorities have so far responded by saying they will encourage "walking, cycling or using public transport" during the Games.
"A key priority for the Mayor is to deliver cleaner air for London which is why he is focussed on targetted measures," said Kulveer Ranger, director for Environment for London Mayor Boris Johnson.
These, Ranger told EurActiv, include for example "using innovative technology such as dust suppresants, encouraging no-idling and installing green infrastructure." There are also longer-term initiatives, he added, such as "introducing low-emission vehicles to the capital, using cleaner buses, banning the most polluting taxies and tightening the Low Emission Zone standards."
'Big scare tactics' or 'Chinese approach'?
As the London authorities prepare their response, Birkett said local authorities usually have two ways of dealing with air pollution. The first is the "big scare tactic" which he said effectively means manipulating people's expectations by telling them not to drive because traffic will be awful. The other way is the "Chinese approach" which involves banning vehicles with odd and an even number plates on alternate days.
Choosing between these two options "is going to be a political hot potato in the UK," Birkett predicted.
A better solution, he said, would be to have "a tighter Berlin-style no-emission zone" in inner London during the 100 days of the Olympics and the Paralympics.
According to Birkett, London's existing low-emission zone, which currently applies in the inner city, is "a weak scheme" that will not be sufficient to tackle the problem.
"Even next year when it is tightened in January, it will still be only a Euro3 standard for vehicles over 1.25 tonnes whereas the German scheme has been Euro4 for diesel since the beginning of 2010," Birkett said, referring to EU standards for car emissions.
At the European level, Birkett says current EU air quality standards should be further tightened, in line with recommendations by the World Health Organisation (WHO): "Legal standards for dangerous airborne particles are about twice the WHO guideline level so they need to be tightened very substantially."