Can Air pollutants negate health benefits of cycling in city urban centres??

What air do you think the people is cars are breathing? Or people standing at the lights beside the cyclists. You aren't really comparing to anything, looking at one in isolation is a bit pointless. To harmless if something is bad or worse, you need to establish a counterfactual or banchmark.

But the short answer yes, at a certain point, if pollution is high enough cycling long durations daily could cause more harm that good. That duration is likely to be extremely long in Ireland, far longer than you would cycle.

You take in 3 times the air when cycling? By what unit. Have a little think about that it it might change you "hence more pollutants" conclusion.

Whilst Electric vehicles may be "Zero emissions" at the exhaust pipe, they emit particulates from tyres and brake pads, and the fact that most EV's weigh about 400 to 500kg+ more than an Ice equivalent... So all those particulate can end up in the lungs...

Not going to be dragged down the rabbit hole of EV's versus ICE cars, needless to say there is such a thing called "non-exhaust emissions" and heavy EV's emit them.

increasingly stringent standards regarding the PM content of exhaust emissions, non-exhaust emissions are quickly becoming the dominant source of PM emissions from road traffic, and are expected to comprise the vast majority of all PM from road traffic as early as 2035. While the uptake of electric vehicles (EVs) will contribute to reducing exhaust PM in future years, non-exhaust PM will not noticeably fall unless targeted policies are undertaken.

A car is breathing in MORE fumes because it takes in air from in front. What's in front but the exhaust of the vehicle in front. It's literally got an intake fan sucking and funnelling it into the cabin. Most cars don't filter out the really bad stuff. What's more someone in a car is mostly likely to be sitting in traffic longer than other forms of transport.

Data can say anything. So going off and looking for a report in the internet you can get one to say whatever you want. Its much the same here as people saying they dont sweat or breathe deeper when they are cycling to when they are sitting down in a car. Biology says they are telling porkies, but im sure they can find a study somewhere that tells them they do if they look hard enough and go past all of the ones that say the opposite while they are looking.

On my commute (which I do on the bike whenever it is not raining or icy) I am flying all the way from Naul to Grand Canal dock. Im cycling at a fair clip all the way to maybe dorset street or phibsboro depending on which way i go, and then have to slow down a bit then. I would consider myself reasonably fit and im certainly not breathing anywhere near as easy as im breathing when driving with windows closed and aircon on either before or when i get to the city. People saying they dont breathe heavier and deeper on a bike than when in a car is just not true.

But each to their own. I personally can tell the difference between what I breathe in when at rest in a car in the city and when im on the bike in the city. In the car ive windows and a filter I guess. On the bike ive nothing. So when in the car at least some of it is getting filtered out. Sure you can even see the dirt on your sleeve when you wipe the sweat of face after cycling through the city.

If anyone wants to convince themselves that the air in the city is somehow healthier if you cycle isnt going to get it cleaned up for us.

I tried a mask on the bike for a couple of weeks a few years ago but couldnt really get used to it.