As is supported by the following article (below), a gradual push is being made towards smaller air pollution sensors. As the issue of air pollution makes itself more prevalent, the development of smaller technology will increase.
Soon, air pollution could be measured by nanosensors on every street corner – https://www.nanowerk.com/nanotechnology-news2/newsid=52978.php?fbclid=IwAR0fnVH8CHPEPjkDpzQsmPoCE1TX-NHxf5yaIfQ3Y7XJvIlC55auaXmXQxo
As it stands, an air pollution sensor was not commercially viable for the watch, with the closest unit available too large and costing £100 a unit. Below is the audio recording of a quote from the supplier of the OPC-R1. The technical data sheet for the sensor is linked below.
Technical data sheet – http://www.alphasense.com/WEB1213/wp-content/uploads/2019/08/OPC-R1.pdf
The size of the sensors can be predicted to reduce, partly by observing Moore’s law, an empirical relationship stating that approximately the number of transistors in an integrated circuit doubles every year (Moore, 1965(reference 5 in appendix)). This theory is indicative of technology becoming smaller however it cannot guarantee the rate at which particulate matter sensors reduce in size. This is due to another limiting factor. The pipes and fan that direct airflow as seen below, (Lattanzio, 2018 (reference 6 in appendix)) need to generate a constant rate of airflow in order to ascertain accurate measurements. This task becomes increasing difficult to achieve accuracy as it reduces in size.
Particulate matter senors will become a suitable size for implementation into the watch however currently it is not possible to accurately depict the time frame in which this will occur. Their price will also become more viable in tandem with their reduction in size as the technology becomes more widely available to tackle this prevailing issue.
