Conflict of interest
The authors declare no conflict of interest.
Acknowledgments
This work was supported by grant NE/100789X/1 from the Natural Environment Research Council UK (NERC) under the Environmental Exposure and Health Initiative. The work of the UK Small Area Health Statistics Unit is funded by Public Health England as part of the MRC-PHE Centre for Environment and Health, funded also by the UK Medical Research Council. The funders had no involvement in the study design, analysis and interpretation of data, writing of the article or the decision to submit the article for publication.