This story initially appeared on High Country News and is a part of the Climate Desk collaboration.

Perhaps no single Christmas customized is extra ubiquitous than placing up the Christmas tree. It originated in jap Europe greater than 500 years in the past, when individuals adorned evergreen bushes with roses or apples as symbols of Eve and the Garden of Eden. Today, that historical custom is a booming enterprise that employs almost 100,000 individuals, garners near $2 billion in income, and harvests 25 million to 30 million pure Christmas bushes yearly—about 30 p.c of them from the Pacific Northwest. Sales of actual Christmas bushes have elevated by almost 20 p.c since 2020, although faux bushes are booming too.

Artificial bushes have drawn criticism for the chemical substances used of their manufacturing, in addition to their carbon footprint. But dwell bushes have drawbacks too. One specifically—the agricultural chemical substances and pesticides, fungicides, and herbicides utilized in tree farming—has drawn remarkably little consideration, partly owing to a scarcity of analysis on the danger to customers or farmworkers.

People who love their conventional inexperienced Christmas bushes, even these fearful about environmental impacts, seldom take into consideration how these bushes are grown. “I’ve used a fake tree for about 10 years,” stated Denise Castro, from Eugene, Oregon. “Prior to that I bought real trees. I never considered that there might be pesticides on trees.” After High Country News reached out to her, she began asking longtime pals in the event that they’d considered it. But pesticides had been both one thing they hadn’t thought-about or weren’t significantly fearful about. “You can count me in on this consensus,” stated Michele Zemba. “Pesticides never crossed my mind when buying a real tree.”

Among the most typical chemical substances utilized by the trade are chlorothalonil, atrazine, glyphosate (higher often called Roundup), and dimethoate, all of which have recognized impacts on human well being. The half-life of a few of these chemical substances ranges from days to years, relying on the chemical concerned and different components. Over time, these pesticides accumulate within the setting, lingering in soil and groundwater and increase in plant and animal tissues—particularly in human beings, who perch on the high of the meals chain.

In Oregon, low ranges of pesticides are generally present in floor and ingesting water. In 2021, researchers at Portland State University released data displaying that forestry-related pesticides had been current in Oregon’s coastal waters, an indication that they had been flowing downstream within the state’s rivers. But it’s troublesome to quantify any specific trade’s contribution to such widespread, low-level air pollution over lengthy durations of time—or to calculate the dangers to customers. Laura Masterson, an natural farmer and former Oregon Department of Agriculture board member, acknowledged that it’s one other hole within the science. “We don’t really understand microdose impacts [of these chemicals] on health.”