Concentration-dependent increase in symptoms due to diesel exhaust in a controlled human exposure study

Juma Orach; Christopher Francis Rider; Agnes Che Yan Yuen; Christopher Carlsten

doi:10.1186/s12989-022-00506-6

Concentration-dependent increase in symptoms due to diesel exhaust in a controlled human exposure study

Part Fibre Toxicol. 2022 Nov 23;19(1):66. doi: 10.1186/s12989-022-00506-6.

Authors

Juma Orach¹, Christopher Francis Rider¹, Agnes Che Yan Yuen¹, Christopher Carlsten²

Affiliations

¹ Air Pollution Exposure Laboratory, Division of Respiratory Medicine, Department of Medicine, Vancouver Coastal Health Research Institute, The University of British Columbia, Vancouver, BC, Canada.
² Air Pollution Exposure Laboratory, Division of Respiratory Medicine, Department of Medicine, Vancouver Coastal Health Research Institute, The University of British Columbia, Vancouver, BC, Canada. carlsten@mail.ubc.ca.

Abstract

Background: Traffic-related air pollution (TRAP) exposure causes adverse effects on wellbeing and quality of life, which can be studied non-invasively using self-reported symptoms. However, little is known about the effects of different TRAP concentrations on symptoms following controlled exposures, where acute responses can be studied with limited confounding. We investigated the concentration-response relationship between diesel exhaust (DE) exposure, as a model TRAP, and self-reported symptoms.

Methods: We recruited 17 healthy non-smokers into a double-blind crossover study where they were exposed to filtered air (FA) and DE standardized to 20, 50, 150 µg/m³ PM_2.5 for 4 h, with a ≥ 4-week washout between exposures. Immediately before, and at 4 h and 24 h from the beginning of the exposure, we administered visual analog scale (VAS) questionnaires and grouped responses into chest, constitutional, eye, neurological, and nasal categories. Additionally, we assessed how the symptom response was related to exposure perception and airway function.

Results: An increase in DE concentration raised total (β ± standard error = 0.05 ± 0.03, P = 0.04), constitutional (0.01 ± 0.01, P = 0.03) and eye (0.02 ± 0.01, P = 0.05) symptoms at 4 h, modified by perception of temperature, noise, and anxiety. These symptoms were also correlated with airway inflammation. Compared to FA, symptoms were significantly increased at 150 µg/m³ for the total (8.45 ± 3.92, P = 0.04) and eye (3.18 ± 1.55, P = 0.05) categories, with trends towards higher values in the constitutional (1.49 ± 0.86, P = 0.09) and nasal (1.71 ± 0.96, P = 0.08) categories.

Conclusion: DE exposure induced a concentration-dependent increase in symptoms, primarily in the eyes and body, that was modified by environmental perception. These observations emphasize the inflammatory and sensory effects of TRAP, with a potential threshold below 150 µg/m³ PM_2.5. We demonstrate VAS questionnaires as a useful tool for health monitoring and provide insight into the TRAP concentration-response at exposure levels relevant to public health policy.

Keywords: Airways; Controlled human exposures; Diesel exhaust; Particulate matter; Symptoms.

Publication types

Randomized Controlled Trial
Research Support, Non-U.S. Gov't

MeSH terms

Cross-Over Studies
Double-Blind Method
Humans
Particulate Matter / toxicity
Quality of Life*
Vehicle Emissions* / analysis
Vehicle Emissions* / toxicity

Substances

Vehicle Emissions
Particulate Matter