This may well be old news to some but as it was new to me I thought I'd just quickly up this information for anyone else out there to read and take note of. I only caught wind of this through an AA engineer who was aware of this.
If you are good with cars you may remember a few years back when manufacturers began putting 'pollen filters' on their cars. The reason I assume given was to stop you from having a dangerous sneezing fit whilst driving at 140 on the autobahn, but apparently given other recent information the real reason may be a little more worrying.
According to research, diesel fumes from modern engines are able to burn the diesel so well that the resulting particles are small enough to be absorbed by human skin and has been attributed to skin and lung cancer. Kind of worrying if you are someone who spends a great deal of time in the car or if you live on a main road.
This information tends to tie in with why the international guidelines given to car manufacturers have become so stringent. Not only do car manufacturers tend to install these 'pollen filters' on their vehicles air vents, but most modern diesel cars now have to have a 'Diesel Particulate Filter'. This is essentially a catalyst which is meant to store the deposits so it can be fully burnt off before it gets into the environment to cause harm.
Trouble is, whilst they lie to our faces about carbon dioxide being the cause of every affliction known to mankind, things such as this are relatively toned down, despite the possible major health complaints it can cause.
The 'diesel particulate filters' are therefore likely nothing to do with carbon dioxide at all, and are more likely a way to try and prevent every commuter from dieing within fifteen years.