dangie
Established Member
By all means take these readings if it is of interest to you. Having done that how will it, or how can it, change your life?
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PM2.5 is lower than outside air in newer trains
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R
RailUK Forums
H&I
Member
I do not think the readings of particulate matter are going to be life changing in and of itself, but these can help someone make an informed decision on their travel options, or whether they should be wearing a mask, for example.
For those asking what this means here is my attempt at a summary, hopefully not too patronising:
You can think of this as being about dust. Normal dust in a house varies from around 1 micrometre to 400 micrometres in size. A micrometre is 1000 times smaller than a millimetre, to give an idea a hair is about 50 micrometres wide.
The OP is measuring quantities of dust that is made up of particularly small particles, each less than 2.5 micrometres in size. These are so small they don't really settle on surfaces but tend to stay in the air and get breathed in. When they get breathed in they are so small that they move into your blood. Research has found that these cause health problems such as asthma, heart disease, lung problems etc. There is not a 'safe level' as such, the more of these particles there are the more likely they are to cause a problem.
The OPs measurements indicated that there is more of this dust in the underground than at street level, but that when in a new train the air conditioning reduces the amount very quickly. There is significantly more of this dust in diesel trains on the national rail network.
What can we do with this information as individuals? Not very much to be honest. But I do find the results interesting, and I would imagine that TfL and train companies carry out their own monitoring that they use to try and buy cleaner trains going forwards.
You can think of this as being about dust. Normal dust in a house varies from around 1 micrometre to 400 micrometres in size. A micrometre is 1000 times smaller than a millimetre, to give an idea a hair is about 50 micrometres wide.
The OP is measuring quantities of dust that is made up of particularly small particles, each less than 2.5 micrometres in size. These are so small they don't really settle on surfaces but tend to stay in the air and get breathed in. When they get breathed in they are so small that they move into your blood. Research has found that these cause health problems such as asthma, heart disease, lung problems etc. There is not a 'safe level' as such, the more of these particles there are the more likely they are to cause a problem.
The OPs measurements indicated that there is more of this dust in the underground than at street level, but that when in a new train the air conditioning reduces the amount very quickly. There is significantly more of this dust in diesel trains on the national rail network.
What can we do with this information as individuals? Not very much to be honest. But I do find the results interesting, and I would imagine that TfL and train companies carry out their own monitoring that they use to try and buy cleaner trains going forwards.
allotments
Member
I've now discovered that my PM2.5 monitor doesn't show any significant change in measured values when exposed to diesel exhaust that the human nose can easily detect.
A quote from
https://www.bbc.com/future/article/20191113-the-toxic-killers-in-our-air-too-small-to-see
"Current pollution meters don’t count the very smallest pollutants – nanoparticles" (2019)
Another quote from https://dieselnet.com/tech/dpm_size.php
"Nearly all diesel particulates have sizes of significantly less than 1 µm...
The maximum concentration of nucleation mode particles occurs at about 10-20 nm. The nucleation mode, depending on the engine technology and particle sampling technique, typically contains only 0.1-10% of the total PM mass, but it often includes more than 90% of the total particle count."
So measured PM2.5 levels don't reflect the level of diesel exhaust particles and gases such as nitrogen dioxide.
A quote from
https://www.bbc.com/future/article/20191113-the-toxic-killers-in-our-air-too-small-to-see
"Current pollution meters don’t count the very smallest pollutants – nanoparticles" (2019)
Another quote from https://dieselnet.com/tech/dpm_size.php
"Nearly all diesel particulates have sizes of significantly less than 1 µm...
The maximum concentration of nucleation mode particles occurs at about 10-20 nm. The nucleation mode, depending on the engine technology and particle sampling technique, typically contains only 0.1-10% of the total PM mass, but it often includes more than 90% of the total particle count."
So measured PM2.5 levels don't reflect the level of diesel exhaust particles and gases such as nitrogen dioxide.