Case-crossover study for the association between increased hospital admissions for respiratory diseases and the increase in atmospheric PM_2.5 and PM_2.5-bound trace elements in Pretoria, South Africa

ABSTRACT

Outdoor PM_2.5 was sampled in Pretoria, 18 April 2017 to 28 February 2020. A case-crossover epidemiology study was associated for increased PM_2.5 and trace elements with increased hospital admissions for respiratory disorders (J00-J99). The results included a significant increase in hospital admissions, with total PM_2.5 of 2.7% (95% CI: 0.6, 4.9) per 10 µg·m⁻³ increase. For the trace elements, Ca of 4.0% (95% CI: 1.4%−6.8%), Cl of 0.7% (95% CI: 0.0%−1.4%), Fe of 3.3% (95% CI: 0.5%−6.1%), K of 1.8% (95% CI: 0.2–3.5) and Si of 1.3% (95% CI: 0.1%−2.5%). When controlling for PM_2.5, only Ca of 3.2% (95% CI: 0.3, 6.1) and within the 0–14 age group by 5.2% (95% CI: 1.5, 9.1). Controlling for a co-pollutant that is highly correlated with PM2.5 does reduce overestimation, but further studies should include deposition rates and parallel sampling analysis.

KEYWORDS:

• Respiratory disorders
• <PM_2.5
• case-crossover
• Pretoria
• Tapp

Acknowledgements

The authors would like to thank the South African Weather Services for the air pollution data of the City of Tshwane and for the meteorology data.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Availability of data and material

Upon request, but then the authors want to be co-authors on the other study’s manuscript.

Ethics approval

Ethics approval was done through the University of Pretoria Research Committee, number 300/20.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/09603123.2023.2229256

Additional information

Funding

Sampling during the study period 16 April 2017 to 31 December 2019 was funded by the National Research Foundation under grant [CPT160424162937]. Sampling during the study period 1 January to 28 February 2020 was funded by the University of Pretoria, South Africa [no grant number].