NIST researchers studied VOC emissions from living Christmas trees and their interaction with ozone. They found that monoterpenes were the main VOCs emitted, decreasing over time and reacting with ozone to produce low levels of formaldehyde. The study concludes that Christmas trees have minimal impact on indoor air quality for most people. Credit: SciTechDaily.com
- Living Christmas trees emit chemicals called volatile organic compounds (VOCs).
- Some of these VOCs can react with ozone, a reactive gas, to create chemical irritants in your home.
- Levels of chemical irritants are low, but may be a potential concern for people who are sensitive to chemical irritants.
Every year during the holiday season, Americans purchase approximately 30 million live Christmas trees. Many families enjoy not only having a live tree in their home, but also smelling the fresh scent it produces. That odor comes from chemicals called volatile organic compounds (VOCs). However, little is known about how much is excreted and whether it affects health.
“Our noses are excellent chemical sensors,” says Dustin Poppendieck, an environmental engineer at the National Institute of Standards and Technology (NIST). “We know these trees are emitting something, but the question is how big is the source? We are investigating which chemicals and how much they are emitting. “We wanted to compare that to other chemical sources in the home,” he said.
To answer these questions, Poppendieck and his colleagues at NIST took a common type of Christmas tree (Dog pine) and sealed it inside a room. They then measured the amount and type of VOCs emitted over a 17-day period. They also investigated whether VOCs react with other components of indoor air to form new compounds.
The team’s findings were published in the journal indoor environment.
NIST researchers placed a common type of Christmas tree in a sealed room for 17 days and monitored and measured the chemicals released from it. These chemicals are called volatile organic compounds (VOCs), which give the smell of pine and can react with ozone to produce byproducts. Researchers found low amounts of these chemicals, which could be a potential concern for people who are sensitive to chemicals. Credit: M. King/NIST
The refreshing scent commonly associated with Christmas trees comes from a group of VOCs called . monoterpenesIt is also found in air fresheners, candles, and some personal care products. In the outdoors, conifer, a group of plants, including most Christmas trees, emit monoterpenes and can affect outdoor air quality. However, little is known about how much monoterpene is released when trees are cut down and placed indoors.
Research also shows that monoterpenes can react with ozone. Ozone in the upper atmosphere acts as a protective barrier against the sun. On the ground, chemical reactions with light produce ozone, which can cause symptoms such as coughs and throat irritation. Ozone also easily reacts with other chemicals in the air to form new compounds. Researchers were therefore interested in observing the effects of ozone in the presence of indoor trees.
They placed it inside an environmentally controlled room so they could measure the chemicals released by the tree in real time. Using a technique that can detect airborne organic compounds, known as proton transfer reaction mass spectrometry (PTR-MS), they measured the VOCs emitted over a 17-day period.
In the experiment, the researchers simulated a home environment. They decorated the tree with a typical holiday lighting setup and illuminated it with bright lights to mimic the day/night cycle. They turned off the lights every 12 hours and watered the tree daily. They brought in outside air at rates typical of a typical home and constantly measured chemicals in the indoor air.
Monoterpenes were the most abundant VOCs emitted by trees. They peaked on the first day and then decreased significantly by the third day. Poppendieck said the concentrations were initially similar to those found in plug-in air fresheners and new homes, but quickly dropped to nearly 10 times the original concentration. Researchers detected 52 different monoterpenes.
The researchers then injected ozone into the chamber to see how it affected indoor air chemistry. They found that ozone reacts with monoterpenes, producing byproducts such as formaldehyde, another type of VOC, and other reactive chemicals. It was found that the introduction of ozone further reduced monoterpene concentrations and increased formaldehyde levels, affecting indoor air chemistry. However, the amount of formaldehyde produced was relatively small at approximately 1 ppb. Formaldehyde concentrations in typical homes in the United States range from 20 to 30 ppb.
For people who are sensitive to VOCs, Christmas trees can be another source of watery eyes and noses, especially if you first bring them indoors. In that case, Poppendieck suggests opening a window near the tree to reduce exposure. In addition, the emission intensity naturally decays over time, so a newly cut tree can be left outdoors or in the garage for three days before bringing it into the house.
“But for most people, this shouldn’t be a big concern,” Poppendieck says. I will continue to decorate the Christmas tree at home. ”
Reference: “Jingle Bells, what do they smell like?” Indoor VOC Emissions from Living Christmas Trees,” by Dustin Poppendieck, Riley Robertson, and Michael F. Link, December 22, 2023. indoor environment.
DOI: 10.1016/j.indenv.2023.100002
Source: scitechdaily.com
