Am I over reacting. Please tell me I’m wrong.

[mjr]

I would be very surprised if the pollution levels in a car with a carbon activated filter were as high as that outside the car.

It depends where outside the car - it may be lower than the pollution at the air intake or the tailpipe of the car in front, but still higher than at the kerbside.

However, even if this were true, the volume of air passed through a cyclists lungs on a similar commute would be vastly greater than that of a motorist/bus or rail passenger on the same journey.

Not vastly - most cyclists are not gonna be going that fast on a route congested by motorists, even if there's a cycle lane, because one should be cautious passing their unexpressive and unpredictable vehicles - and it also means that what pollution there is spending less time lingering in the lungs and potentially being absorbed - lungs are not a filter that all air passes through.

The cyclist is also far more likely to be hit than those using other transport methods.

More likely than most but still very unlikely.

 

[jefmcg]

Please describe such a route. I

You're welcome
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Seriously, the OP has one of the nicest city commutes I could imagine. As mentioned he could go through Richmond Park. He could cross the river at Kingston and come up through mostly quiet roads to Twickenham, then follow the river past Marble Hill, Orleans House and on through Syon House (how many people get to pass a recently restored Capability Brown garden twice a day?) He could follow the Thames path along the river and through gardens and a field of cows and around the outside of Kew Gardens, joining the road at Kew Bridge and then following the reasonably quiet roads along the river or he could continue past the rowing clubs to Chiswick Bridge and on to his destination. If it was me, I'd mix it up and take different options each day.

The cyclist is also far more likely to be hit than those using other transport methods.