Carbon monoxide exposure inside UK road vehicles: a pilot study

Objective

To test the following hypotheses:

 (i) CO is present inside the passenger cabins of road vehicles driven by members of the general public in the UK;

 (ii) in-cabin CO is due, at least in part, to internal exhaust leakage; and

(iii) the use of handheld dataloggers by laypeople can generate data relevant to the above two objectives.

Design                      

Pilot study.

Setting                       

Two centres: privately-owned cars in Chesham and Amersham, and cars used by engineers at Southern Gas Networks in Epsom.

Participants            

28 participants entered the study, through online local recruitment (first centre, n=21) and through line management (second centre, n=7), driving 33 vehicles. The study excluded vehicles carrying smokers.

Primary outcome measure

Parts per million CO, logged continuously during journeys. Mean journey per cent ppm CO was calculated and peak journey ppm CO noted.

Methods                   

Measurement of CO using mobile-compatible dataloggers.

Results                     

33 vehicles returned 230 journey logs in all. 20 (61%) of cars logged non-zero CO. Mean all-journey average was 6.629ppm CO. 10 journeys measured ≥10ppm CO at least once. Peak single-journey average CO was 192.174 ppm. Some patterns of CO ingress were suggestive of internal exhaust leakage.

Conclusions             

This is the first public-engagement UK-based study of CO levels within vehicles. It shows that in-cabin average CO levels are non-zero overall, and in some cases markedly raised. 

Chronic low-level CO exposure has a range of harmful effects. In addition to causing hypoxic stress, it contributes to cardiovascular disease, generation of reactive oxygen species, and demyelination of white matter. Pregnant women, the unborn and children are especially vulnerable to its effects, which include gestational-specific harms.

Adding in-car air quality measurement to the MOT would benefit public health, alerting vehicle owners, who may be asymptomatic, to raised in-vehicle exhaust levels. Routine MOT air quality testing would have the additional benefit of capturing wider data on the problem, as would larger studies of similar design.

Methods
Testers measured in-cabin COppm, using the Kane COA1 Carbon Monoxide Detector Adapter. Although the maximum range of the sensor was 999 COppm, the app supporting the datalogger generated some graphs with readings in excess of this level. For calculation purposes, values have been capped at 999ppm. 

Data is left in arithmetic form, with right-skewing unaltered.

Data analysis was performed with custom scripts written in Lua.

Readings from one datalog (see Supplemental Material) were set aside due to likely artefactual interference on the sensor.