The Ireland Air Quality Alerts Bot
What does it do?
Every hour or so the bot takes a look at the air quality data
provided by the Environmental Protection Agency under a creative commons license
For each location where the most recent reading for PM2.5
is over 54 it will tweet the current value.
There is no particular standard for an instant reading, but there are defined standards for a 24 hour mean value. Generally you will see evening peaks for a few hours
that may be extremely high, but the average over 24 hours could still be classed as good or fair. The EPA is mostly concerned about the 24 hour mean so they report the
Air Quality Index for Health
. This means that they
will not normally report that air quality is poor until after the episode, and will continue to report that a place has poor AQIH for the whole of the following day, by which time the
particulates may have fully dispersed and readings could be very low.
To simplify things I am only concerned with fine particulate matter (PM2.5
) and the levels corresponding with High (7,8,9) and Very High (10) so that is PM2.5
from 54 to 70 and 71 or more.
I don't report an AQIH level because that is defined as a 24 hour mean, the aim is to provide a timely alert so that people can take action based on the health advice given by the EPA.
Are the sensors accurate?
Yes. They are very expensive high quality scientific instruments, the values have been cross checked with low cost sensors and when the EPA sensors report
high values it will tend to be on still, cold nights when people are burning coal and turf. If they are reporting values over 100 then it will be noticeably smokey.
What causes pollution? Is it traffic or dirty industry?
It is solid fuel burned for domestic heating in open fires and stoves. The SAPPHIRE project
studied the composition of air pollutants
and attributed a large proportion to peat, wood and coal. Traffic is about 1% (less than sea salt) and only domestic heating leads to the extreme evening accumulations that generate levels
of particulates that are a concern for health. Whilst traffic and industry do produce pollution (and CO2
which is a concern globally) they don't appear to be a significant contributor to localised
daily pollution of levels that are a concern for public health.
Can we do anything about it?
Yes, we could. Switch to cleaner heating sources, especially on cold still nights. In descending order the cleanest are electric heat pumps, electric resistive heating, gas and oil. On a public
policy level the government could provide financial incentives for switching to cleaner more economical heating sources.
What should I do if I see a tweet about poor air near to me?
You might want to consider following the EPA advice relating to reducing physical activity
and if you were thinking
about lighting the fire you could use an electric heater instead.
Why is the number reported in the tweet not on the graph?
The bot looks at the values reported as the latest reading. The graph shows hourly averages. I think that the sensors report a value every 15 minutes,
we see one of the four readings, which may be above or below the average for the hour.
This generally results in the bot tweeting an alert a bit before the graph itself reaches the threshold - which is a good thing.