Many people with asthma ride, but traffic and haze can raise the risk of attacks, so ride with a plan. A meta-analysis of 22 studies linked PM2.5 to more emergency visits and admissions for asthma (Orellano et al., 2017). Check the air before you go, keep your reliever on you, and do not trust a loose mask to do the job.
This is general information, not medical advice. Follow your own asthma action plan.
Picture the lane at a red light: a bus exhaust at your knee, a truck ahead, your visor fogging from your own breath.
That is where a rider with asthma spends the commute. Motorcycle riders in Makassar breathed PM2.5 at four times the level seen in cars (Patel et al., 2016). So the question is not whether the air matters. It is what you can actually control.
Key takeaways
- A meta-analysis of 22 studies found PM2.5 linked to more asthma emergency visits and hospital admissions, with a pooled odds ratio of 1.028 (Orellano et al., 2017).
- Four retail face masks let 3% to 68% of diesel soot reach the wearer's face in resting tests, mostly through poor fit (Cherrie et al., 2018).
- For a tested N95, leakage around the edges let through about 7 to 20 times more particles than passed through the filter itself (Grinshpun et al., 2009).
- WHO's 24-hour PM2.5 guideline is 15 µg/m³, and the US EPA tells people with asthma to follow their action plan on high-pollution days (WHO, 2021; AirNow, 2023).
The research behind this
Peer-reviewed studies this post is built on. Each card says what was measured, what was found, and what it can't tell you.
Outdoor air pollution and asthma exacerbations
- What they measured
- A systematic review and multilevel meta-analysis of 22 case-crossover studies (2000 to 2016) using emergency visits and hospital admissions as the measure of moderate or severe attacks.
- What they found
- PM2.5 was significantly associated with exacerbations (pooled odds ratio 1.028, 95% CI 1.009 to 1.047). So were NO2, CO and ozone. PM10 and SO2 were not significant overall.
- Can't tell you: it counts hospital-level attacks, not mild symptoms, and it pools studies from many places, not a motorcycle lane.
Outdoor air pollution and asthma
- What they measured
- A review of clinical studies from the previous five years on particles, ozone, nitrogen dioxide, sulphur dioxide and mixed traffic pollution.
- What they found
- Traffic and power generation are the main urban sources, and the evidence that outdoor pollution can worsen existing asthma has built up over decades. The likely mechanism is oxidative injury to the airways.
- Can't tell you: evidence for pollution causing new asthma is less consistent, and a review gives no personal risk number.
Do retail face masks work in Beijing?
- What they measured
- Nine retail masks tested for filter penetration with diesel exhaust. Four were then worn by volunteers in a chamber, resting and active, with black carbon measured inside and outside the mask.
- What they found
- Filter material let through 0.26% to 29%. On faces, total inward leakage ran 3% to 68% resting and 7% to 66% active. Only one mask stayed under 10% in both.
- Can't tell you: a chamber with diesel soot, four mask types, and no one riding at speed.
Particle penetration through the seal
- What they measured
- One N95 respirator and one surgical mask on 25 people doing standard fit-test exercises, plus breathing manikins, across 5,250 particle-size and exercise readings.
- What they found
- For the N95, leakage at the face seal exceeded filter penetration by about 7 times at 0.04 µm, 10 times at 0.1 µm and 20 times at 1 µm. For the surgical mask the ratio was 4.8 to 5.8.
- Can't tell you: it used health-care masks in a lab, not a rider on a vibrating bike.
Commuter exposure and masks in Makassar
- What they measured
- Handheld particle counters on motorcycles, pete-pete minibuses and cars in Eastern Indonesia's largest city, plus tests of surgical masks, bandanas and motorcycle masks.
- What they found
- Motorcycle PM exposure was 4 times higher for PM2.5 and 13 times higher for PM10 than in cars. Only surgical masks consistently lowered exposure (p<0.01).
- Can't tell you: a single city, short sampling runs, and average PM2.5 there was only 9 µg/m³ with peaks to 139.
A facemask and blood pressure in Beijing
- What they measured
- A randomised crossover trial: 15 healthy adults walked a Beijing city route for 2 hours with and without a highly efficient facemask, with heart and blood pressure monitoring.
- What they found
- Systolic blood pressure was lower with the mask (114 vs 121 mmHg) and heart rate variability improved over 24 hours.
- Can't tell you: 15 healthy people walking, not people with asthma on a bike, and heart outcomes rather than lung ones.
What the studies actually measured
Start with the asthma link. Orellano's team pooled 22 studies that tracked emergency department visits and admissions against daily pollution (Orellano et al., 2017).
PM2.5 came out with a pooled odds ratio of 1.028. That is a small step up in risk per unit of exposure, but it was consistent enough to be statistically significant (Orellano et al., 2017).
Guarnieri and Balmes explain why. Traffic and power generation are the main urban sources, and pollutants probably injure the airway lining through oxidation, which drives inflammation (Guarnieri and Balmes, 2014).
Then the exposure side. Patel carried particle counters through Makassar traffic and found motorcycle riders took in 4 times the PM2.5 and 13 times the PM10 of car passengers (Patel et al., 2016).
The last three studies are about masks. Cherrie and Grinshpun measured leakage, and Langrish tested whether a good mask changes body outcomes (Cherrie et al., 2018; Grinshpun et al., 2009; Langrish et al., 2009).
Ride with filtered air
Filters haze PM2.5 on every ride
Easi Breezi clips onto any helmet and feeds you H11 HEPA-filtered air. Bike-powered, no batteries, no charging.
Traffic pollution is a known asthma trigger
If you already have asthma, you do not need a study to tell you smoke and exhaust make you cough. The studies tell you how consistent the pattern is.
Orellano found significant links for PM2.5, nitrogen dioxide, carbon monoxide and ozone. In children, the links were significant for NO2, SO2 and PM2.5 (Orellano et al., 2017).
That matters for riders because a motorcycle lane mixes all of them. Exhaust gives you NO2 and CO, sunlight adds ozone, and haze adds PM2.5.
Motorcycle riders in Makassar breathed four times the PM2.5 and 13 times the PM10 of people in cars on the same roads.
Source: Patel et al., 2016One caution. The Makassar city average PM2.5 was only 9 µg/m³, with readings up to 139 (Patel et al., 2016). Your own route, in your own haze season, will be different. Check it.
Check the number before you start the engine
The simplest control is timing. The US EPA's guidance for particle pollution is blunt: on the Unhealthy for Sensitive Groups level (AQI 101 to 150), people with asthma should follow their asthma action plan and keep quick-relief medicine handy (AirNow, 2023).
Sensitive groups there include people with lung disease. AirNow also tells them to make outdoor activity shorter and less intense, and to watch for coughing or shortness of breath (AirNow, 2023).
At the Hazardous level (AQI 301 and up), the advice for sensitive groups is to stay indoors and keep activity low (AirNow, 2023).
The WHO yardstick is stricter than most local alerts. Its 24-hour PM2.5 guideline is 15 µg/m³, and the annual one is 5 (WHO, 2021).
Look at the PM2.5 figure, not only the index colour. Our post on what the AQI number does not measure explains why.
Time of day can help too. Our guide to the best time to ride to avoid pollution covers the pattern in detail.
Most masks leak where you cannot see it
The obvious fix is a mask. The evidence says be careful which one, and how it sits.
Cherrie bought nine retail masks in Beijing. In the lab their filter material let through 0.26% to 29% of soot. On volunteers, the total inward leakage ranged from 3% to 68% while resting (Cherrie et al., 2018).
The authors blame poor facial fit. Only one of the four masks tested on faces stayed under 10% in both resting and active tests (Cherrie et al., 2018).
Grinshpun found the same story in a different test. For a standard N95, leakage around the face edge let through about 7 to 20 times more particles than the filter fabric did (Grinshpun et al., 2009).
Body and face movement had a pronounced effect on that leakage (Grinshpun et al., 2009). On a motorcycle you turn your head, grip, buffet at speed and sweat. That is a harsh fit test.
In Makassar, only surgical masks consistently cut exposure. Bandanas and motorcycle masks did not (Patel et al., 2016).
A mask rated N95 or KN95 protects you fully, whatever the fit.
The rating describes the filter. Leakage at the face seal was about 7 to 20 times larger than leakage through the filter in the N95 tested (Grinshpun et al., 2009).
A good mask can still help. In Langrish's trial, wearing a highly efficient facemask on a Beijing walk lowered systolic blood pressure by 7 mmHg on average and improved heart rate variability (Langrish et al., 2009). The word that matters is "highly efficient", and the trial used healthy walkers.
We cover the seal problem in detail in our pollution mask post.
Breathing effort is a separate problem
People with asthma often find a tight mask uncomfortable, because anything that adds breathing resistance can feel like an attack starting. We found no peer-reviewed study that measures this on motorcycle riders, so we will not give a number.
What you can do is test any mask or filter on a short, safe, stationary trial first. If it makes you wheeze or panic, it is the wrong tool for you, whatever its rating says. Ask your doctor.
Try new gear at home or on a short low-traffic loop, with your reliever on you. Never debut it in the middle of a haze day.
Filtering at the helmet changes the problem
A mask depends on a seal against your skin. A helmet-mounted filter works differently: it draws air through filter media before it reaches your face.
Easi Breezi clips onto your helmet and passes the air you breathe through H11 HEPA media that stops at least 95% of PM2.5. See the clip-on helmet air purifier.
It is a particle filter. It does not remove carbon monoxide, nitrogen dioxide or ozone, which also trigger asthma in the Orellano data, and it is not a medical device. It does not replace your reliever or your doctor.
For the wider picture, read the helmet air filtration guide.
- Agree your action plan with your doctor. AirNow tells people with asthma to follow it and keep quick-relief medicine handy on high-pollution days (AirNow, 2023).
- Check PM2.5 before you leave. Compare it with WHO's 15 µg/m³ 24-hour guideline (WHO, 2021) and use the live haze page.
- Shorten or move the ride on bad days. AirNow advises shorter, less intense activity for sensitive groups.
- Do not rely on a loose mask. Leakage ranged from 3% to 68% in volunteer tests (Cherrie et al., 2018).
- Consider filtering at the helmet. The Easi Breezi clip-on air purifier filters PM2.5 at your intake.
Frequently asked questions
Can you ride a motorcycle with asthma?
Many people do, but it is a question for your doctor. Traffic pollution is linked to more asthma exacerbations, so a plan for high-pollution days matters (Orellano et al., 2017).
Does haze trigger asthma?
PM2.5, the main part of haze, was significantly linked to asthma exacerbations in the Orellano meta-analysis (Orellano et al., 2017). Follow your action plan when readings are high.
Is a face mask enough to ride in polluted air?
Not always. Soot leakage ranged from 3% to 68% across four retail masks on volunteers (Cherrie et al., 2018), mostly through the edges.
What air quality level is too high to ride with asthma?
There is no single safe line for everyone. AirNow advises people with asthma to follow their action plan from AQI 101 and to stay indoors at the Hazardous level of 301 and above (AirNow, 2023).
Sources
- Orellano, P., Quaranta, N., Reynoso, J., Balbi, B., Vasquez, J. (2017). "Effect of outdoor air pollution on asthma exacerbations in children and adults: Systematic review and multilevel meta-analysis." PLOS ONE. doi.org/10.1371/journal.pone.0174050
- Guarnieri, M., Balmes, J.R. (2014). "Outdoor air pollution and asthma." The Lancet. doi.org/10.1016/s0140-6736(14)60617-6
- Patel, M., Shibata, T., Wilson, N., Maidin, A. (2016). "Challenges in evaluating PM concentration levels, commuting exposure, and mask efficacy in reducing PM exposure in growing, urban communities in a developing country." Science of the Total Environment. doi.org/10.1016/j.scitotenv.2015.10.163
- Cherrie, J.W., Apsley, A., Cowie, H., Steinle, S., Mueller, W., Lin, C., Horwell, C.J. (2018). "Effectiveness of face masks used to protect Beijing residents against particulate air pollution." Occupational and Environmental Medicine. doi.org/10.1136/oemed-2017-104765
- Grinshpun, S.A., Haruta, H., Eninger, R.M., Reponen, T., McKay, R.T., Lee, S.A. (2009). "Performance of an N95 filtering facepiece particulate respirator and a surgical mask during human breathing: two pathways for particle penetration." Journal of Occupational and Environmental Hygiene. doi.org/10.1080/15459620903120086
- Langrish, J.P., Mills, N.L., Chan, J.K., Leseman, D.L., Aitken, R.J., Fokkens, P.H. and colleagues (2009). "Beneficial cardiovascular effects of reducing exposure to particulate air pollution with a simple facemask." Particle and Fibre Toxicology. doi.org/10.1186/1743-8977-6-8
- World Health Organization (2021). "WHO global air quality guidelines: particulate matter (PM2.5 and PM10), ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide." who.int
- US EPA AirNow (2023). "Air Quality Guide for Particle Pollution." airnow.gov
Written by Ash, mechanical engineer and founder of Easi Breezi, building an active HEPA filtration system for motorcycle helmets (Patent Pending). Based between Hong Kong and Bali, riding daily in the traffic this blog writes about.