Tag Archives: Commuters

‘No significant difference’ in air pollution exposure between rush-hour commuters and others

People who commute during rush hour are obviously exposed to more traffic-related air pollution than those who do not. However, a new study comes to show that the difference is not very meaningful, or statistically significant.

Image via Pixabay.

Air pollution is bad for you, we all know that. But we all need to make rent, so we brave the streets to get to work on time, often through engine exhaust, dust, and other pollutants. In order to gauge just how much more significant this exposure is during rush hour compared to other times of day, researchers at the George Mason University College (GMU) College of Health and Human Services monitored commuters during their trips using personal air pollution monitors.

Although rush-hour commuters are definitely exposed to more air pollution from traffic than their peers, they explain, the difference is not that large.

Just as bad

“This is one of the first studies to utilize in-vehicle monitoring, specifically on-board diagnostics data loggers, to understand real-world commuting behaviors for environmental health,” said Dr. Jenna Krall, assistant professor at the GMU and lead author of the study. “Linking these data with personal air pollution monitoring allowed us to better understand how commuter characteristics are associated with sources of air pollution exposures.”

The team wanted to understand how factors such as departure time, frequency, and commute length influence our exposure to air pollution. For the study, they employed personal air pollution monitors to see how much air pollution different participants were actually exposed to over their commute, then mixing this in with the time and route they took. They were particularly interested in exposure to fine particulate matter (PM2.5), which in this context mainly come from traffic-related sources including exhaust, brake wear, and salts used to de-ice roads.

All in all, the study included 46 women in northern Virginia who commuted using their personal vehicles and were monitored over a 48-hour period. The authors found that differences between those commuting during rush hour and the rest were not statistically significant.

Still, the findings are especially useful in the context we find ourselves in right now. The coronavirus generally attacks our respiratory system, which is most exposed to air pollution. We’re also seeing a gradual easing away of measures implemented during the pandemic, and more people are getting called back to the office from home. Understanding the effect of air pollution and patterns of exposure to it could go a long way towards preserving public health.

That being said, the findings still lack a proper background into which they can integrate. Commuters form incredibly complex systems, and there’s still a lot of unknowns regarding this behavior.

“The current research cannot tell us whether modifying commutes, for example by avoiding highways or commuting outside of rush hour, will lower traffic pollution exposures for commuters. More research is needed to determine what changes would be effective to lower exposures,” says Krall.

The paper “Commuter types identified using clustering and their associations with source-specific PM2.5” has been published in the journal Environmental Research.

Driving to work? You’re probably inhaling dangerous chemicals

If ever there was a time to reconsider how you get to work every day, it’s now.

A study found that those who commute with their car in California are likely exposed to dangerous chemicals that increase the risk for cancer and birth defects — way over the threshold for exposure established by state government legislation.

Image credit: UC Riverside

Bad for you, bad for the planet

US adults spend an average of 6% of their time within an enclosed vehicle, a large amount of which is spent commuting. In the US, a person spends an average of 52.8 min per day commuting to work. This isn’t just bad for the planet (by producing more pollution and greenhouse gas emissions), it’s also bad for you: longer commute times are strongly associated with negative health outcomes such as shorter sleep, obesity, and poor physical/mental health

People who spend a longer amount of time in vehicles are also exposed to higher concentrations of particulate matter, carbon monoxide, VOCs, ozone, and flame retardants. This effect is so pronounced that people experiencing long commutes over years and decades likely represent a sub-population vulnerable to excess exposure to vehicle-borne chemicals. Now, a new study adds even more weight to those concerns.

A group of researchers at the University of California Riverside wanted to better understand the potential risk associated with exposure to vehicle-specific chemicals as a function of commute time. They focused on five Prop 65-listed chemicals detected within vehicle interiors: benzene, formaldehyde, di phthalate, dibutyl phthalate, and trisphosphate.

California’s Proposition 65 (Prop 65) requires businesses to inform people about exposure to chemicals known to cause cancer, birth defects, or other reproductive harm. Prop 65-listed chemicals represent a wide range of naturally occurring and synthetic chemicals that include additives or ingredients in pesticide formulations, common household products, food, drugs, dyes, or solvents. In some cases, Prop 65-listed chemicals that are used in indoor products have the potential to migrate, abrade, or off-gas from end-use products and accumulate in indoor environments. The presence of Prop 65-listed chemicals in indoor air and dust has been well documented, suggesting that people may be exposed to these chemicals through inhalation of air and ingestion of dust.

While several studies have evaluated the potential risk to Prop 65-listed chemicals detected within indoor environments, we don’t know all that much about the risk of these chemicals in regards to exposure within personal vehicles. Due to the small size of a car, chemicals emitted from its interior have the potential to be concentrated.

Chemicals such as phthalates, volatile organic compounds (VOCs), flame retardants, and hydrocarbons — several of which are Prop 65-listed — are commonly detected within interior vehicle dust. Prior studies have demonstrated that the concentration of certain chemicals within vehicle interiors were 2- to 3-fold higher compared to indoor concentrations. In their new study, the researchers at UC Riverside found that the average commuter in California is breathing unsustainably high levels of benzene and formaldehyde, both of which are used in automobile manufacturing. These are highly carcinogenic substances, with benzene carrying the additional risk of reproductive and developmental toxicity. The levels at which these substances are inhaled by many commuters is considered unsafe.

The study calculated the daily dose of benzene and formaldehyde being inhaled by drivers with commutes of at least 20 minutes per day. This showed that up to 90% of the population in Los Angeles, San Diego, Orange, Santa Clara, and Alameda counties have at least a 10% chance of exceeding cancer risk from inhaling the chemicals, based on having 30-minute average commute times.

The presence of these compounds within vehicles can be attributed to extensive use in different vehicle parts. Formaldehyde is used in carpets, leather, and paints within vehicles, resulting in off-gassing and high concentrations within indoor air. Meanwhile, benzene is linked to fuel- and exhaust-related emissions that accumulate in the cabin of operating vehicles. It’s also used to produce styrene, nylon, and phenol

“These chemicals are very volatile, moving easily from plastics and textiles to the air that you breathe,” David Volz, UCR professor of environmental toxicology and co-author of the study, said in a statement. Volz suggested keeping the windows open during car rides if possible so to reduce the concentration of these chemicals thanks to the airflow.

The study was published in the journal Environmental International.

Commuters, traffic, and offices make cities hotter during the week

Humans have a much more direct impact on weather than you’d think. The huge number of commuters pouring into cities during the week actually makes them warmer and shifts local wind, rain, and cloud patters, a new study found.

Image credits Pat McKane / Pixabay.

During the week, all the people, cars, and operating buildings in cities pour out a lot of heat into the environment. Recently, Nick Earl at the University of Melbourne, Australia found that you can actually tell if it’s a workday or the weekend by the average temperature. Based on more than 50 years’ worth of recordings from Australia’s Bureau of Meteorology, Earl and his team showed that morning temperatures in Melbourne are typically 0.3 degrees C hotter on Thursday or Friday than on a Sunday.

“That’s just the average,” he says. “Some days will heat up more, if for example there isn’t much wind.”

It’s not surprising, given that the city sees some 250,000 extra people and heavy traffic every weekday compared to the weekends. All the air conditioning in office buildings also plays a part. This weekly cycle caught Earl’s eye in the first place.

“Nothing in nature occurs on a weekly cycle, so it must be due to human activity.”

Earl and his team have shown that Sydney, Brisbane, and Adelaide have similar weekly temperature cycles. Tokyo or Moscow also show the same cyclicity. Other weather phenomena, such as wind speeds, precipitation, and cloud cover also tend to be greater in urban centers during the week. These are effects of higher heat and pollution levels, Earl says.

“For example, warmer temperatures in the city create convection, which can suck in more air from outside, affecting wind speeds and direction,” he added.

Knowing how human activity impacts weather and average temperatures can help adapt to freak weather patterns and save lives. This can become especially useful in hot areas or countries, such as Australia, where heatwaves can claim the lives of a lot of people.

“For example, during heatwaves, you could ban cars from the city so that it doesn’t warm up as much.”

It could also help urban planners counteract the effect, for example by requiring roofing to be made of deflecting material which can cool down cities.

The paper will be presented at the annual conference of the Australian Meteorological and Oceanographic Society in Canberra next month.