Fine particulate matter is a prime example of variation in safety standards. In many chemicals we talk seriously of one in a million risk. PM risks are by far larger, probably between 1:1000 to 1:100. But European Union has not been able to adopt standards that WHO recommends, and many other countries do not see them necessary. This is an example of the necessity to increase risk/risk comparisons to give balanced guidance to population. According to DALY-analyses, fine particulate matter is the most important environmental health risk. Therefore it certainly requires strict standards.

Dear Jouko,

Thanks a lot for your answer. I agree with you that standard setting for PM2.5 and PM10 seems to be dominated by cost-benefit analysis which lead to larger risk in the order of 1:100 to 1:1000. My question, however, goes into the PM10 standards. In Chile, we just revoked the annual PM10 standard. The reason are that annual PM2.5 are the important fraction and that coarse particles likely do not produce chronic health effects. My question is if you agree with that statement or you think it is important to keep an annual PM10 standard. I have been looking into the evidence (cited by EPA ISA 2009), and many studies of chronic effects are based on PM10 (because there is no PM2.5). I feel that is not a good idea to remove the annual PM10, at least if you do not put a strict PM10 daily standard.

Hope you have a minute to keep my thoughts, I am advising some people here in Chile and this topic is important.

Pablo

Hi Pablo, I think this depends on the capacity to measure PM2.5. If every city is able to do that, additional PM10 may be superfluous. But if PM2.5 information is limited, PM10 helps, because as a general measure of particulates it tends to correlate to PM2.5 to some extent and gives guidance to authorities. Maybe somebody else would disagree?

My understanding is that obligatory mouth breathers will inhale the coarse fraction into the pulmonary tract and that is why the US still retains the PM10 standard.

Hi Pablo,

James is right; the PM10 fraction can be inhaled but its penetration deeper into the lung is restricted to particle size so the smaller fraction within this course measure will penetrate further than others. As a result I can see an argument to say that PM2.5 is becoming more the size of concern so that should be measured (plus there are a number of research papers that speak to PM2.5 affects being more dominant than PM10 overall). Anecdotally, I do know that a number of our local authorities have abandoned PM10 measurement in favour of PM2.5 (mostly using TEOMs in case that is of interest) despite there remaining objective air quality standards for both PM10 and 2.5.

Another way of perhaps making the decision is to consider what proportion of PM10 is PM2.5? Speaking only for the UK as a whole, the proportion of PM2.5 within PM10 has been increasing because I suspect we are improving capture and control of coarser particulates. For the UK approx. 66% of PM10 is PM2.5 although in my city, it is nearer 75%. Not sure if relative proportion could be a way to decide which is the better fraction to measure? If 2.5 is the better one based on % and health outcome, then perhaps a stronger 2.5 fraction is better. Control of PM2.5 will thus drive a control of PM10 anyhow so perhaps there is no need for PM10 standard merely a robust PM2.5 one.

The above said, PM needs to be measured and I agree with Jouko that the decision may depend on access to equipment in the field or the cost of deploying them to measure the smaller fraction.

Hope that helps.

Simon.

particulate matter are generally categorized according to its size ,PM10 does not penetrate deep into the lung, so may be exhaled in upper respiratory airway. only PM2.5 (fine PM) or less can reach the alveoli and get enter the blood and cause adverse health effects. so fine PM is important to measure.

Any PM10 or TSP that is inhaled superficially will eventually be swallowed, be exposed to the acid environment of the stomach and may potentially have toxic effects through non-respiratory pathways.

May I add my 50p? Calculated PM10 and PM2,5 risks are higher for PM than for idividual chemicals. However, individual toxicants can be banned and totally avoided, whereas PM cannot be avoided, and are formed also by natural processes.

During my toxicological education the chemical nature was important; for PM is appears to be neglected (at least in experiments). Thus I still do not know, whether being a small particle by itself is toxic (silicosis?) or whether PM are toxic in relation to their chemical composition and adsorbed compounds. Interestingly, for salt crystals (coastal regions) these particles are excluded. What about other PM with specific chemistry?

Measuring particle size is simple, calculating risk is problematic, and conclusions are hard to validate. Unfortunately (at least in Germany) limit values are political arguments. I am not aware that any attempt to reduce PMs have had an effect on the public health (if properly corrected for confounders). Thus revoking and completely ignoring pollution (PM) may be a bad idea, following the letter but not the meaning of pollution control likely is just as bad.

Interesting comment from Johannes. I am aware of studies that indicate that an increase of 10ug/m3 in PM2.5 and to a lesser extent PM10 can be related to cardiovascular events but not aware of any that have shown improvements in health outcomes with reduction in PM levels. (I also find it 'interesting' that natural sources as outlined are excluded).

The chemical nature of PM I believe is probably important and am working on my PhD (started in the last few weeks) to try and characterise the physical and chemical nature of PM2.5 and PM10 and then relate that to exposure potential amongst our population.

A study in the United States has shown that a decrease in PM10 concentrations of 10 μg/m³ was associated with an increase in life expectancy of 0.61 ± 0.20 years (Pope et al., 2009). These authors concluded that "A reduction in exposure to ambient fine-particulate air pollution contributed to significant and measurable improvements in life expectancy in the United States"

The paper is available on ResearchGate:

Pope, C.A., Ezzati, M., Dockery, D.W., 2009. Fine-particulate air pollution and life expectancy in the United States. The New England Journal of Medicine 360, 376-386.

Article Fine-Particulate Air Pollution and Life Expectancy in the Un...

The most obvious study on improvement is: "Effect of air-pollution control on death rates in Dublin, Ireland: an intervention study" by Luke Clancy, Pat Goodman, Hamish Sinclair, Douglas W Dockery, Lancet 2002; 360: 1210–14.

Whether risk is associated with chemical or physical characteristics is a good question and it seems that jury is still out.

Thanks all for the comments. I have been inquiring this with a lot of people and I think one of the most important source of information I got is two new documents from WHO. They review health eveidence for new Air Quality Guidelines. You can check question A4, where they state that there are good scientific reason for thinking there is long term effects of PM10 that are not explained by PM2.5 and a bunch of papers to suuport this. This for us is crucial as Chile just revoked the annual PM10 standard, which I think is not a good idea.

http://www.euro.who.int/en/health-topics/environment-and-health/air-quality/publications/2013/review-of-evidence-on-health-aspects-of-air-pollution-revihaap-project-final-technical-report

http://www.euro.who.int/__data/assets/pdf_file/0006/238956/Health-risks-of-air-pollution-in-Europe-HRAPIE-project,-Recommendations-for-concentrationresponse-functions-for-costbenefit-analysis-of-particulate-matter,-ozone-and-nitrogen-dioxide.pdf

Pablo

This is something we are doing in Chile...

http://www.eldinamo.cl/2014/03/14/experto-alerta-de-peligros-para-la-salud-de-eliminacion-de-norma-mp-10/