# World Health Organization - conversion
**URL:** https://community.purpleair.com/t/world-health-organization-conversion/5716
**Category:** Feature Requests
**Created:** [July 24, 2023, 3:00pm UTC](https://community.purpleair.com/t/world-health-organization-conversion/5716 "2023-07-24T15:00:27Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Gary](https://community.purpleair.com/u/Gary)
#### Post date: [July 24, 2023, 3:00pm UTC](https://community.purpleair.com/t/world-health-organization-conversion/5716/1 "2023-07-24T15:00:27Z")
Would you consider adding a WHO conversion factor to the list of those currently available? Standards matter and relying upon US EPA’s conversion under estimates the impact of air pollution on human health. The differences between the EPA and WHO standards are substantial. Below is a comparison of the two standards for PM 2.5.
```
…………. 24 hour…….. Annual
```
EPA……… 35 mg/m3……… 12 mg/m3
WHO……. 15 mg/m3………… 5 mg/m3
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### Author:  [@Gary](https://community.purpleair.com/u/Gary)
#### Post date: [November 30, 2023, 7:43pm UTC](https://community.purpleair.com/t/world-health-organization-conversion/5716/2 "2023-11-30T19:43:47Z")
> [@Gary](#):
>
> Would you consider adding a WHO conversion factor to the list of those currently available? Standards matter and relying upon US EPA’s conversion under estimates the impact of air pollution on human health. The differences between the EPA and WHO standards are substantial. Below is a comparison of the two standards for PM 2.5.
I’m still waiting for a reply (11/30/23). Is there a technical reason for not including a WHO conversion factor? It would seem pretty straight forward.
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### Author:  [@Kieran](https://community.purpleair.com/u/Kieran)
#### Post date: [March 6, 2024, 11:29pm UTC](https://community.purpleair.com/t/world-health-organization-conversion/5716/3 "2024-03-06T23:29:52Z")
Hi Gary,
Our apologies for the late response. We have responded to this question in a different thread here: [WHO scale for PM2.5?](https://community.purpleair.com/t/who-scale-for-pm2-5/1385/)