Diesel traffic — respiratory effects on asthmatic persons

After posting about a research on diesel pollution exposure on school buses previously, I thought it will be good to look deeper into the effects of such exposure. The journal article that I looked at did not provide any particularly surprising information to me, since I already had a rough idea about how polluted diesel exhaust is, and how they pose various problems to our respiratory tracts. What this article taught me more about is some specific respiratory effects (it is from a health journal, the New England Journal of Medicine!) and some considerations when it comes to possible experimental design.

Close up picture of diesel exhaust fumes. Source: http://www.autoguide.com/auto-news/wp-content/uploads/2012/06/Diesel-Exhaust.jpg [Last accessed: 26 February 2015]

McCreanor et al (2007) did a research on the short-term respiratory effects of exposure to diesel traffic in asthmatic persons in an urban, roadside environment. What this research aims to do is to build on research from previous studies that were conducted under laboratory conditions — previous studies have not been entirely consistent and exposure to those pollutants may not reflect that of real conditions. McCreanor et al (2007) suggests that these discrepancies may be due to interactions between different pollutants, or that pollutants under laboratory conditions may have removed. Instead of conducting the research indoors, they got participants to expose themselves to diesel traffic by the streets.

They got 60 adults with mild or moderate asthma to walk for 2 hours along Oxford Street, London, and Hyde Park on a separate occasion (I briefly mentioned in my first post that Oxford Street was raised in the spotlight just recently in 2015 for extremely high nitrogen dioxide levels!). The study was limited to winter months to avoid other variables such as exposure to pollen. As expected, participants had significantly higher exposure to fine particles, in particular, PM2.5 when walking along Oxford Street. There were also higher exposure to other ultrafine particles, elemental carbon, and nitrogen dioxide. As a result, participants with prolonged exposure to air pollution by the streets recorded consistent respiratory effects such as a reduction in the forced expiratory volume in 1 second and forced vital capacity. Respiratory tracts were also inflamed after prolonged exposure, and these effects are more severe for those with moderate asthma.

Of course, having an experimental design as such will lead to a lot more confounding variables — the authors mentioned that the respondents produced symptomatic responses, but other variables such as traffic noise may have played a part in increasing stress levels, which may trigger the onset of asthmatic symptoms too.

Diesel exhaust is also cancerous — according to NHS Choices, WHO’s International Agency for Research on Cancer (IARC) decided to classify diesel exhaust as carcinogenic instead of “probably carcinogenic” in 2012 after there is sufficient evidence that diesel exhaust is a cause of lung cancer.

How bad are diesel exhaust fumes? As a reference, The Daily Mail quoted Kurt Straif, director of the IARC department that evaluates cancer risks, who mentioned that the effects of breathing diesel exhaust is of the same magnitude as that of passive smoking. (So, try not to stay indoors too when there are people smoking in the room!)

Picture of a cigarette. Source: http://www.healthoxygen.com/blog/wp-content/uploads/2013/08/quit-smoking.jpg [Last accessed: 26 February 2015]

(And since there are 2 pictures showing a lot of smoke, Diesel Exhaust + Cigarette smoke = Smoky Streets indeed! Can’t resist not mentioning the blog name, haha. Even though the contents of this blog should be much more than just this two topics!)


McCreanor, J., Cullinan, P. Nieuwenhuijsen, M.J., Stewart-Evans, J., Malliarou, E., Jarup, L. Harrington, R. Svartengren, M., Han, I., Ohman-Strickland, P., Chung, K.F., Zhang, J. (2007). ‘Respiratory Effects of Exposure to Diesel Traffic in Persons with Asthma’. The New England Journal of Medicine 357: 2348-2358.

NHS Choices (2012). ‘WHO: ‘Diesel Exhaust Fumes Cancerous”. [Online] Retrieved from: http://www.nhs.uk/news/2012/06june/Pages/who-classes-diesel-vehicle-exhaust-fumes-as-carcinogen.aspx [Last Accessed: 25 February 2015]

The Daily Mail (2012). ‘Diesel exhaust fumes are ‘major cancer risk’ and as deadly as asbestos and mustard gas, says World Health Organisation’. [Online] Retrieved from: http://www.dailymail.co.uk/health/article-2158574/Diesel-engine-exhaust-fumes-major-cancer-risk.html [Last Accessed: 26 February 2015]


Some updates on pollution by firecrackers

I posted 3 days ago about the likelihood of air pollution due to fireworks in Beijing during the upcoming Chinese New Year celebrations. Over the next few days, I managed to read some news updates regarding the situation. Indeed, what authorities predicted came true: real time air-quality data from Beijing recorded a sharp jump in PM2.5 levels immediately after midnight. The article on IBT Pulse tells you the whole story with a few pictures that helps illustrate the point, do take a look at the article here!

The South China Morning Post also reports that “the air quality index rose from around 50 to 456 within a few hours, with average PM2.5 levels hitting 413 micrograms per cubic metre – more than five times the national safe standard – at about 1am” (As a comparison, at 20th Feb, 9pm, Singapore’s hourly PM2.5 level is at 57 at the central area, and about the 25 to 40 range for other areas (north, south, east west); the bigger numbers are the overall PSI readings, not the PM2.5 readings. The PM2.5 readings are in a smaller print.)

Source: Screenshot by me!

Source: Screenshot by me!

Hopefully, these updates will provide you with a better picture of the pollution caused by firecrackers!


FlorCruz, M. and Poladian, C. (2015). Chinese New Year 2015 Fireworks: Lunar New Year Celebrations Spur Air Pollution Debate. International Buisness Times. Pulse. [Online] Retrieved from: http://www.ibtimes.com/pulse/chinese-new-year-2015-fireworks-lunar-new-year-celebrations-spur-air-pollution-debate-1822008 [Last accessed: 20 February 2015]

Li, J. (2015). Beijing Welcomes Auspicious Snowfall amid heavy pollution over Lunar New Year. South China Morning Post — China. [Online] Retrieved from: http://www.scmp.com/news/china/article/1719584/beijing-welcomes-auspicious-snowfall-amid-heavy-pollution-over-lunar-new [Last accessed: 20 February 2015]

Happy Chinese New Year! (And let’s not forget about pollution)

It’s Chinese New Year soon, and I thought I could have a post about firecrackers. In particular, firecrackers causing pollution (after all, this is a pollution blog!)

Firecrackers are banned in Singapore, but they are still rampant in cities such as Beijing. According to the International Business Times, Beijing’s city government has attempting to cut down firecrackers in the city. While this may not be such a big deal in Singapore (Firecrackers were completely banned since 1 August 1972 when the Dangerous Fireworks Act came into operation), in many other places firecrackers are still seen as part of the Chinese New Year tradition — the loud sounds and lights are believed to ward away evil spirits.

For Beijing’s case now, other than firecrackers being a fire hazard, it is a major source of street pollution with red confetti expected to be scattered across the streets, and with the weather this coming Friday (the 2nd day of the Chinese New Year) expected to be windless, city authorities have anticipated that smoke from firecrackers are likely to persist in the air for a long period of time. These smoke, a result from combustion, contains pollutants such as PM2.5, which is harmful to health. As cited by Wang et al (2007), these fine aerosols which consist of sulfur dioxide, carbon dioxide, suspended particles, and traces of heavy metal poses threats to human health. This study also highlights the problem of air pollution due to these fireworks, by drawing on the chemistry of these fireworks, and found ions, metals and black carbon in aerosol samples. Pollutants were also found to be much higher during the festive season than from other days.

Results from this report tallied with observations over other years; for instance, Channel News Asia reported that on Lunar New Year’s Eve, 2013, the concentration of PM2.5 grew from 150 micrograms per cubic metre to 346 micrograms per cubic metre within an hour due to the fireworks.

While some residents are grateful for the authorities’ decision to cut down on firecrackers, some remained disgruntled. One resident said

“If the authorities are serious about tackling pollution, they should tackle industrial pollution. Setting off fireworks is just a once-a-year event. It is not as bad as industrial pollution.” (Source: CNA)

I felt that this line of reasoning, is unfortunately, problematic. If we have to tackle pollution issues, it takes more than just managing large pollution sources, and it definitely takes more than the authorities to do their job. As citizens, we do have responsibility towards our environment — small actions such as cleaning up after our trash, using environmentally friendly cars if we can afford them, minimising our use of plastic goods, and in this case, reducing the number of firecrackers may not seem to matter, but the effects add up over the long run. Admittedly, cultural practices may be hard to change…

In any case, happy Chinese new year to all and may you all have an auspicious year ahead! 🙂

Happy Chinese New Year!


Channel News Asia (2015). Beijing Air Quality set to worsen as Lunar New Year Approaches. [Online] Retrieved from: http://www.channelnewsasia.com/news/asiapacific/beijing-air-quality-set/1665138.html [Last accessed: 17 February 2015]

Sim, S. (2015). Beijing Chinese New Year Fireworks spark crackdown over air pollution concerns. International Business Times. [Online] Retrieved from: http://www.ibtimes.com/beijing-chinese-new-year-fireworks-spark-crackdown-over-air-pollution-concerns-1818664 [Last accessed: 17 February 2015]

Singapore Infopedia (2013).Regulating the use of Fireworks. [Online] Retrieved from: http://eresources.nlb.gov.sg/infopedia/articles/SIP_2013-10-04_181113.html [Last accessed: 17 February 2015]

Wang, Y., Zhuang, G., Xu, C., and An, Z. (2007) The air pollution caused by the burning of fireworks during the lantern festival in Beijing. Atmospheric Environments. 41(2). pp. 417- 431.

BreezoMeter (EDIT: Not available in SG!)

I came across an article today which introduces a relatively new app (just released in January 2015) that not only allows users to know the quality of the air that they are breathing in, but also where can they find cleaner air in the city. It’s called BreezoMeter and is available on Google Play!

Apparently, it does offer suggestions of cleaner routes around the city, which will be great for people who are planning to jog or cycle around — it will be rather ironic if one tries to exercise to keep fit, but ended up subjecting him or herself to higher exposure of polluted air instead.

I thought the idea was really great as not only does it propose suggested routes, it also provides a set of advice for the user based on the current air quality. From what i observed from the pictures, air quality is represented through qualitative means (good, moderate, etc), which eliminates excessive numbers; this makes it a good app for the general public as the information that it provides can be easily understood.

NOTE: Wanted to give this app a try since ratings and reviews look good, but it does not work in Singapore, unfortunately 😦 (only available in the US). Wanted to take a look at the GooglePlay store to see if there are other apps available, and I found that the National Environment Agency (NEA) has an app, myENV, that provides data on air quality readings too (together with various different readings such as Wind, UV Index, Dengue Clusters, and so on). I still find BreezoMeter more attractive based on the description and looks/supposed functionality of the app alone. Perhaps such apps will attract more users and even achieve its goal better (users being aware of the air quality around them) if they offer additional functionality (such as suggesting exercise routes) instead of solely presenting data because there will be a greater impetus to use the app.

Diesel Pollution — Exposure to Diesel Exhaust on School buses

I came across a study by Dr John Wargo on “Children’s Exposure to Diesel Exhaust on School Buses”, which I found rather interesting. It has found that majority of school buses in the USA are powered by diesel fuel, and diesel exhaust has been identified as a probable human carcinogen. In this study, it was found that buses contain fine particulate concentrations (PM2.5) much higher than average levels along fixed monitoring stations in Connecticut. The study also highlighted several circumstances were highlighted in which level of fine particles were higher; these included situations where buses are running through high traffic, or when buses are running with windows closed, and when buses queued to load/unload children. The study, published under Environment and Human Health Inc (EHHI), can be accessed here! (There is a pretty useful summary report and a briefing note(?) by the US Environmental Protection Agency too, for those who want an overview of the issue)

The issue had a specific context that I can relate to — transport to school (I recall my own secondary school days where I had to squeeze on public buses that barely inched forward during peak hours). I never took a school bus on a frequent basis, but I suppose that the issues are similar; with so many people, be it children or adults, travelling along the roads everyday, diesel pollution is probably one aspect of pollution of the streets that we should be concerned with.

We have school buses in Singapore (that are not yellow) too! Just that they are under the service of various private bus companies and usually serve as tour buses too. Image Retrieved from: http://www.bedoktransport.com/data1/images/home3.jpg

Dr Wargo, together with a few other authors, have also written a report on “The harmful effects of vehicle exhaust“, which provided a broader discussion to the issue of vehicle exhaust pollution. Specific health problems are also highlighted (asthma and other respiratory problems), with children and elderly at much higher risk.

In Singapore, issues of diesel pollution exists too. For instance, the The Ministry of Environment and Water Resources, Singapore (MEWR) reports that the main sources of tiny particulate (such as PM10) are exhaust fumes from motor vehicles, in particular diesel vehicles. Some policies that have been in place to address this problem includes ensuring that the Euro VI standard for new diesel-powered vehicles are met starting from 1 January 2018 (National Environmental Agency, 2014). MEWR has also been encouraging the use of green vehicles (with the Green Vehicle Rebates since January 2001). Other measures in place includes the Chassis Dynamometer Smoke Test (CDST) for testing diesel vehicles that are found to not comply with NEA’s smoke emission threshold since 1 September 2000. Also, from 1 January 2007, All diesel-driven vehicles will also have to undergo the CDST during their mandatory inspections.

As a side note, I particularly liked how The New Scientist puts this particular study (Dr Wargo’s research on diesel exhausts) across as:

“The buses that take our children to school should be safe places. But… (these buses) are polluted by diesel exhausts.” (Source. Last Accessed 8 February 2015)

By describing the situation as such, it prompted us (or myself, at least) to take a look at the situation in more detail because it seemed counter-intuitive that a school-bus is supposed to take children to a place of safety and learning, but may instead be bringing them towards poor health (through the prolonged and cumulative exposure of diesel exhausts).


Environmental Protection Agency (n.d). ‘What you should know about Diesel Exhaust and School Bus Idling’. Retrieved from: http://www.epa.gov/reg3artd/diesel/School_bus_idling_MAR.pdf [Last accessed: 8 February 2015]

National Environmental Agency (2014). ‘Singapore will Usher in Duro VI Emission Standard for Diesel Vehicles from January 2018’. [Online] Retrieved from: http://www.nea.gov.sg/corporate-functions/newsroom/news-releases/singapore-will-usher-in-euro-vi-emission-standard-for-diesel-vehicles-from-january-2018 [Last accessed: 8 February 2015]

Ministry of the Environment and Water Resources (2008).  ‘Chapter 1 — Air’. State of the Environment 2008 Report Singapore. pp. 16-25. [Online] Retrieved from: https://app.mewr.gov.sg/data/ImgCont/1233/016-025%20Air.pdf [Last accessed: 8 February 2015]

Wargo, J. (2002). ‘Children’s Exposure to Diesel Exhaust on School Buses’. Retrieved from: http://www.ehhi.org/reports/diesel/diesel.pdf [Last accessed: 8 February 2015]

Wargo, J., Wargo, L. and Alderman, N. (2006). ‘The Harmful Effects of Vehicle Exhaust. A Case for Policy Change’. Retrieved from: http://www.ehhi.org/reports/exhaust/exhaust06.pdf [Last accessed: 8 February 2015]

Lichens — bioindicators of air pollution

Lichens have been used as air quality bio-indicators because of their sensitivity towards pollutants including ammonia, heavy metals, and in particular, sulfur dioxide. This is due to their efficient absorption systems (they take in nutrients from water and the surrounding air) which results in the accumulation of sulfur dioxide when exposed to high levels of sulfur dioxide pollution. The use of lichens as an air quality indicator was first discovered when many lichens disappeared from trees in England after the Industrial Revolution, which also resulted in an increased occurrence of acid rain. Since then, many research has been done on the impacts of air pollution on lichens, and it has been established that urban lichen distributions are related to patterns of urban air pollution.

One such research by Coffery & Fahrig (2012) attempts to identify the relative importance of vehicle pollution (based on road density and bus traffic at each measurement site), moisture, and colonisation sources in determining lichen distribution within the city (Ottawa, Canada). Both lichen richness and extent of lichen cover was monitored. Results of the study (84 lichen sites were surveyed) indicated that vehicle pollution is most strongly linked to lichen cover (on trees) within 300m with insignificant variation of lichen richness in relation to vehicle pollution. This supported the use of the Lichen Diversity Index (LDI) as an indicator of urban vehicle pollution patterns. From an ecologist point of view, increasing the availability of lichen colonisation sources such as trees will be more efficient in promoting lichen diversity than controlling vehicle pollution.

Many of these study of lichens, however, are from Europe and North America. Related studies are lacking in other regions around the world. There is a study by Ng et al (2006) on lichens as bioindicators of heavy metal pollution in Singapore. The species Dirinaria picta (see below for picture!) is monitored because they can be found on the trunks of commonly found trees in Singapore. Results of these study have shown that there is potential for D. picta to be used extensively as a bioindicator for the monitoring of atmospheric metal contamination in the Southeast Asian region.

Picture of Dirinaria picta. Image retrieved 3 February 2015, from http://www.sharnoffphotos.com/lichensB/lic_img2/dirinaria_picta_2.jpg

With so many trees along Singapore’s streets, it will be interesting to see how monitoring of lichens can be used to compare different levels of pollution in Singapore. This will make a rather interesting and doable fieldwork project for us students to learn more about air pollution too.


Air Pollution Information System (2011) Lichen Diversity Value (LDV) (European Method). [Online] Retrieved from http://www.apis.ac.uk/node/1210 [Last accessed: 3 February 2015]

Coffey, H. M.P. and Fahrig, L. (2012). ‘Relative effects of vehicle pollution, moisture and colonization sources on urban lichens’. Journal of Applied Ecology. 49(6) pp. 1467-1474.

Ng, O. H, Tan, B.C. and Obbard, J. P (2006). ‘Lichens as Bioindicators of Heavy Metal Pollution in Singapore’. Environmental Monitoring and Assessment. 123(1-3), pp. 63-74.

Unwin, H. (2009) Using Lichens as Indicators of Air Quality. [Online] Retrieved from http://www.theecologist.org/campaigning/cleaner_air_water_land/363298/using_lichen_as_indicators_of_air_quality.html [Last accessed: 3 February 2015]