生きたクリスマスツリーが屋内の空気化学に影響を与えることをNISTの研究者が発見(Live Christmas Trees Affect Indoor Air Chemistry, NIST Researchers Find)

2023-12-23

2023-12-22 米国国立標準技術研究所(NIST)

◆毎年約3000万本の生のクリスマスツリーがアメリカで販売され、その新鮮な香りは揮発性有機化合物（VOCs）に由来します。
◆国立標準技術研究所（NIST）の研究者は、ドゥーグラス・ファーという一般的なクリスマスツリーを17日間密閉したチャンバー内で検査し、ツリーが放出するVOCsの種類と量を調査しました。研究によれば、モネテルペンと呼ばれるVOCsが最も多く放出され、初日にピークに達し3日目には急激に減少しました。また、オゾンの存在下でモネテルペンが反応し、ホルムアルデヒドなどの新しいVOCsが生成されましたが、これらの量は一般的な家庭の濃度範囲内であることが示されました。
◆VOCsに敏感な人々は初めてツリーを持ち込んだ際に鼻水や涙の原因になる可能性があり、その場合は窓を開けたり、新しく切り倒されたツリーを数日間室外やガレージに置いたりすることが勧められています。

＜関連情報＞

ジングルベル、この匂いは何？生きたクリスマスツリーからの屋内VOC放出 Jingle bells, what are those smells? Indoor VOC emissions from a live Christmas tree

Dustin Poppendieck, Rileigh Robertson, Michael F. Link
Indoor Environments Available online: 22 December 2023
DOI:https://doi.org/10.1016/j.indenv.2023.100002

Highlights

•Live Christmas trees can emit a range of chemicals into indoor air.
•Some of these emitted chemicals can react with ozone, impacting indoor air chemistry.
•The placing of a live Christmas trees indoors is a source of VOCs comparable to sources such as air fresheners, building materials, and fragranced products.

Abstract

Every year in the United States conifers are purchased to serve as Christmas trees in homes where they emit volatile organic compounds (VOCs) to the indoor environment. Although many studies have measured the ecosystem-level emissions of VOCs from conifers outdoors (characterizing monoterpene, isoprene, and aldehyde emissions), little is known about VOC emission rates once a conifer is brought indoors. Using a proton transfer reaction-mass spectrometer we characterized the VOCs emitted from a freshly cut Douglas Fir for 17 days in an environmentally controlled chamber. Ozone injections were also performed to analyze indoor chemistry that may occur. Introduction of the tree into the chamber increased the response of 52 mass spectra signals detected by the PTR-MS by at least 500 counts per second (cps) compared to background levels, with concentrations sharply decreasing after the first two days. Monoterpenes were emitted from the tree at a rate of 12.4 mg h⁻¹ the first day and fell to 1 mg h⁻¹ by day three. Overall, monoterpene emissions from this Douglas fir were initially comparable to other strong indoor monoterpene sources (fragranced products and air fresheners) but decayed quickly and, within days, were smaller than other common indoor sources. Addition of ozone to the chamber resulted in decreased monoterpene concentrations that coincided with modest increases in formaldehyde. Four other emitted VOCs were tentatively identified due to their large increase within the first few hours of the tree placed in the chamber, behavior during ozonation, or pattern of accumulation over time.