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The Effect of Vehicle Exhaust on Plants and Humans

One of the main contributors of air pollution is vehicle exhaust. When a vehicle is on, whether in motion or idling, exhaust is released from the tailpipe. There are some cities that try to reduce the amount of exhaust released from idling buses. In the greater Philadelphia area for example, there are signs posted at bus stops that ask the drivers to turn off the bus if they are going to wait for a specific amount of time. But, there are vehicles other than public transportation buses that cause air pollution. As Delaney et al. stated in their article, “Transit industry gears up and responds to climate challenges”, most of land transportation vehicle emissions - 85% - belong to personal automobiles (2009). Since automobiles are the main contributors to transportation emissions relative to surface vehicles, commuting greatly impacts the effect of exhaust on the people and the environment around the cars. Drivers spend 1-1.5 hours per day traveling; mainly due to commuting, (Zurrbier et al., 2010).   People spend a large chunk of time commuting in cars, or other diesel or petrol fueled vehicles, which significantly increases the likelihood that they are inhaling the vehicle exhaust from their own vehicle and the vehicles around them, (Zurrbier et al., 2010). Related or unrelated to the statistics about commuting, the mortality rate, due to air pollution, is 50,000 deaths per year in the United States, (Palmgren et al., 2003). This number might increase in the future; the amount of diesel cars on the road is increasing as the years continue, (Rudell et al., 1999). 

Diesel exhaust is composed of many chemical compounds: carbon monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO2), hydrocarbons (HCs), and aldehydes,” (Rudell et al., 1999). The particles that are emitted from petrol and diesel engines can be large to ultrafine particles in size. The particles are created in the engine, the exhaust pipe, or directly after release at high temperatures, (Palmgren et al., 2003). These compounds, or particles, are released into the air from vehicles and are inhaled by humans and other animals. In the Soll-Johannin et al. paper, the authors described the particles as a formation of “incomplete combustion of fossil fuels,” (1998). The incomplete combustion particles vary in their adverse effects on animals. Some particles are not as harmful as other particles; the toxicity depends on the size of the particles. The larger the diameter the more harmful the particle is in human lungs, (Schwartz, 2000). 

It is easy to imagine that the more a person works near roads with heavy traffic the more particles that they will inhale during their lifetime. But, the workers do not, necessarily, need to be outside to experience the effects of the particles. Rudell et al. found out in their paper that “drivers of lorries, buses, cars, and heavy equipment vehicles are exposed to the exhaust through the air inlet of the vehicle,” (1999). It is harder to avoid the particles that are emitted from your vehicle and the vehicles around you when they are seeping in through the air inlet of your automobile. The particles not only impact the driver, but the passengers as well. In public transportation buses and school buses, the passengers are just as harmed as the driver. In fact, the school bus is a major component of the inhaled diesel particulate matter for a child, (Marshall & Behrentz, 2005). 

For children that do not ride school buses, the location of their homes or daycare centers is a major contribution to the levels of inhaled diesel particulate matter. In their study, Burr et al. showed a positive association between air pollution from heavy traffic on the street of residence and respiratory disorders in the children, (2004). While children are more susceptible to the effects of air pollution because of “their higher breathing rates, and developing lungs and immune system,” does not mean that adults should ignore the warnings, (Housten et al., 2006). Adults can acquire illnesses from air pollution like children. 

Compared to children, adults are around air pollution for longer periods of time, due to commuting. Even though adults have a lower breathing rate, and stronger lungs and immune systems, they are not invincible against air pollution. For individuals of all ages, air pollutants have a strong association with negative effects on the respiratory health of an individual. Some symptoms of air pollution contamination in individuals are: problems with the eyes, nose, and throat, labored breathing, coughing, phlegm, wheezing, and headaches, (Rudell et al., 1999). While these symptoms seem mild and benign, long term exposure to high levels of air pollution can cause chronic disease, (Burr et al., 2004). It does not take much to be exposed to air pollution. The particles move with the air. In Philadelphia, Pennsylvania, airborne particles, at common concentrations for the city, were associated with daily deaths, (Schwartz, 2000). 

The airborne particles that move with the wind and are inhaled by animals are deposited in the lungs and will stay in the lungs for long periods of times, up to several months, (Palmgren et al., 2003). There is a large possibility that exhaust is carcinogenic in human beings. A carcinogenic pathogen increases the likelihood that the possessor of the substance will develop cancer. Soll-Johanning et al. found an increased risk of 25% for cancer, a 60% increase for men and a 160% increase for women who were exposed to air pollution for long periods of time, (1998). Drivers of buses, trucks, and heavy equipment, for their job, have increased risk of developing cancer the longer they work at their jobs. Jobs, on average, last 8 hours per day and 5 days a week. Drivers of vehicles are constantly exposed to the carcinogens when they are just traveling. Driving as a part of their jobs increases the time individuals are exposed to the air particles from their exhaust. 

Human beings are not the only organisms affected by vehicle exhaust. “Motor vehicles emit a complex mixture of airborne pollutants, many of which may have ecological effects,” (Bignal et al., 2008). The environment takes a brutal impact from the chemical compounds released into the air. There are obvious effects, like the depletion of the ozone layer and less obvious effects such as damage to plants. The leaves of plants can get clogged with the particles released from vehicle emissions making it hard for the plant to photosynthesize.  Many plants are killed off by vehicle exhaust. On the edge of highways there is a certain distance before plants start to grow with vigor.

Bignal et al. experimented on the effect of vehicle emissions and bryophyte plants near roadways. Near highly used roads there were more nitrogen-tolerant plants than in areas further from the road; vehicle emissions release nitrogen into the atmosphere. The ions emitted by vehicles do not last long in plumes in the air. Near busy roads some of the exhaust falls to the ground in soot particles, which can affect the plants, (Jayaratne et al., 2010). As noted in the Bignal et al. experiment the bryophytes were not found in highly urbanized areas close to pollution sources, because of the high concentrations of smoke and sulfur dioxide, (2008). Even if the plants still exist in the locations near highly traveled roads they, similarly to humans, have increased susceptibility to environmental stresses, (Bignal et al., 2008).   

Even though the impacts of vehicular emissions are widely studied, people still use vehicles for a majority of their trips. Projjal Dutta, the Director of Sustainability for the Metropolitan Transportation Authority for New York City, believes that “Americans have not been connecting the dots between transportation and CO2 emissions,” (Delaney et al., 2009). The problem is not the lack of proof, but, the willingness of the global population to connect vehicular transportation with harmful chemical compound emissions. 

There are other forms of transportation that people can explore besides personal vehicles. The obvious alternative is public transportation, even though diesel buses are shown to have the same health and environmental impact as petrol and diesel automobiles. There is a recent interest in clean buses, a mixture of cleaner fuel and better emission control technology. The electric trolley is also another investment that many cities should make. 

There are other modes of transportation beyond motorized vehicles; people could start to walk or bike to places instead of driving their car. Though, in an odd twist of fate, bicycling and walking increase exposure to air pollutants. Zuurbier et al, in their study, found that bikers have an increased inhalation which increases the amount of particles that are inhaled into their lungs, (2010). The location of the cycling route influences the amount of particles inhaled. High vehicle occupancy roads release more pollution and are more of a risk for non-vehicular travelers. But, this information should not be a deterrent for cyclist or pedestrians. The health benefits of walking and cycling outweigh the risks of air pollution illness. An increase in bikers and pedestrians will decrease the number of drivers. This decrease will lower the vehicular emissions and create a cleaner and healthier environment for walkers and bikers.

City planners should realize that vehicle exhaust is a dangerous combination of chemical compounds that should not be inhaled. Structure of cities should change to include more bike lanes and pedestrian walk ways in areas with lower levels of traffic. Public transportation planning should also take a high priority in decision making. If public transportation is convenient for the citizens, less people would decide to drive. Delaney et al. stated that to make a better public transportation system, it would require support from the public, which is “difficult to garner in our car-dependant society,” (2009). Society needs to change views of what is important for vehicles and realize the detrimental effects exhaust is having on human health and environmental function. 

Bibliography

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Burr, M.L., G. Karani, B. Davies, B.A. Holmes, & K.L. Williams. 2004. “Effects on respiratory health of a reduction in air pollution from vehicle exhaust emissions”. Occupational and Environmental Medicine. 61: 212-218.

Delaney, B.T., B. Thomson, & B. Previdi. 2009. “Transit industry gears up and responds to climate change challenges”. Environmental Claims Journal. 21(4): 313-321.

Jayaratne, E.R., X. Ling, & L. Morawska. 2010. “Ions in motor vehicle exhaust and their dispersion near busy roads”. Atmospheric Environment. 44: 3644-3650.

Marshall, J.D., E. Behrentz. 2005. “Vehicle self-pollution intake fraction: children’s exposure to school bus emissions”. Environment Science and Technology. 39: 2559-2563.

Palmgren, F., P. Wåhlin, J. Kildesø, A. Afshari, & C.L. Fogh. 2003. “Characterisation of particle emissions from the driving car fleet and the contribution to ambient and indoor particle concentrations”. Physics and Chemistry of the Earth. 28: 327-334.

Rudell, B., U. Wass, P. Hörstedt, J.-O. Levin, R. Lindahl, U. Rannug, A.-L. Sunesson, Y. Östberg, R. Sanström. 1999. “Efficiency of automotive cabin air filters to reduce acute health effects of diesel exhaust in human subjects”. Occupational and Environmental Medicine. 56(4): 222-231.

Schwartz, J. 2000. “Daily deaths are associated with combustion particles rather than SO2 in Philadelphia”. Occupational and Environmental Medicine. 57(10): 692-697.

Soll-Johanning, H., E. Bach, J.H. Olsen, F. Tüchsen. 1998. “Cancer incidence in urban bus drivers and tramway employees: a retrospective cohort study”. Occupational and Environmental Medicine. 55(9): 594-598.

Zuurbier, M., G. Hoek, M. Oldenwening, V. Lenters, K. Meliefste, P. van den Hazel, & B. Brunekreef. 2010. “Commuters’ exposure to particulate matter air pollution is effected by mode of transport, fuel type, and route”. Environmental Health Perspectives. 118(6): 783-789.