New York is a city of smells, yet the scent of weed is breaking through.
Smoking violation complaints to the city’s 311 system are up an average of 86% since adult-use marijuana was legalized in 2021 — compared against the prior decade. Smoking complaints in parks are likewise up 44%. The records do not specify if weed or cigarettes are the culprit, but tobacco use rates have declined sharply in the city over the last two decades.
These grievances may have to do with the chemistry of cannabis itself and the physics that governs how its smoke moves — but researchers are also digging into the perception of weed and how it influences peoples’ acceptance of cannabis use in public spaces. The best way to understand the present and navigate the future might be through scientific understanding of the substance — and how that influences opinion.
A study published Aug. 11 in the journal JAMA Network Open found adults in the United States increasingly perceive secondhand exposure to cannabis smoke as safer than tobacco smoke — though this view doesn’t reflect the science that suggests otherwise. But this greater acceptance of cannabis could explain why New Yorkers might be more likely to tolerate weed use on a park bench whereas lighting a cigarette might draw side-eye.
An effort is underway to quantify all these elements — chemistry, physics and human behavior — to inform the next phase of cannabis use where it’s legalized, like New York. These researchers are less concerned with smell complaints than with the negative ingredients of secondhand cannabis smoke — which are also inherently produced by cigarettes and wildfires.
Dr. Beth Cohen is a professor of medicine at the University of California in San Francisco and senior author of the JAMA study.
“Do we have enough reassuring evidence to say yes, it is okay to be exposing people to secondhand cannabis smoke?” Cohen said. “I certainly don’t think we do. We do need to know a lot more about the long-term health outcomes.”
At the same time, limiting public consumption of cannabis comes at the risk of promoting less equitable policies. New York City smoking laws effectively make it difficult to indulge unless you possess your own home, as restrictions exist for public housing and dwellings with three or more units. (Even then, 311 smoking complaints involving apartments and residences are up, too).
Further, the smell of weed was historically used as justification for a police stop or search. While the scent irritates some and can be the signifier of more offensive complaint or dog whistling , some advocates say the now common smell is an important reminder of progress since the days of marijuana prohibition.
It’s a complicated situation, as cannabis usage begins to outpace tobacco. In New York state, about 12% of people smoke cigarettes and about 13% have used cannabis in the last month (closer to 6% use it daily). Complaints around cannabis smoke are seemingly getting louder, despite growing acceptance.
Cannabis smell and smoke — what’s happening?
Almost every part of a cannabis plant — the dried flowers, leaves, stems and seeds — can be used in various ways, but smoking is the most common. More than 200 aroma compounds have been identified in cannabis, and within this chemical group, terpenes are widely seen as responsible for the various smells and tastes associated with different strains.
For example, among major weed groups, a cannabis indica cultivar might have a stronger, more pungent smell, while a cannabis sativa cultivar might have a scent that’s more woody and citrusy. A hybrid of the two might emit an odor that’s more floral.
People can smell cannabis — and tobacco smoke, too — at extremely low concentrations, explained Suzaynn Schick, an associate professor of medicine at the University of California in San Francisco. Schick studies the health effects of air pollution and has extensively examined secondhand tobacco smoke.
But health researchers make a distinction between catching a random whiff of weed in a park versus an extended exposure to secondhand cannabis smoke. Schick also pointed out that while cannabinoid compounds like THC and CBD have some medicinal benefits, the concentration of these in secondhand smoke is too low to have any positive biological effect.
The chemical makeup of exhaled smoke in the air after a drag on a cigarette or a joint is “mostly the same,” she said.
Researchers found that a cannabis joint’s emission rate of fine particulate matter was 3.5 times that of a tobacco cigarette.
Since about 2017, she and her team have analyzed the air quality in public places where cannabis is smoked, like outdoor concerts. Results so far suggest outdoor smoking of weed raises levels of fine, inhalable particulate matter to a degree that exceeds what the Environmental Protection Agency defines as healthy. New Yorkers may remember this fine particulate matter is a component of wildfire smoke.
While there’s a need for more research, studies so far suggest secondhand cannabis smoke is more threatening than the majority of the public realizes. In a 2021 study looking at indoor use of tobacco and cannabis, researchers found that a cannabis joint’s emission rate of fine particulate matter was 3.5 times that of a tobacco cigarette. Cannabis smoke also has many similar toxins and carcinogens as tobacco smoke. The same is true for sidestream smoke—the smoke that passes into the surrounding air, rather than the lungs.
A 2020 paper comparing the two substances also found that potentially hazardous particles in cannabis smoke are 29% larger than tobacco smoke, and the total particulate matter in a joint is of a mass 3.4 times greater than that of a cigarette. Smaller particles are thought to travel deeper into the lungs and have a higher health risk, though larger particles carry more inertia and can more easily stick in upper airways.
And while the size differences may sound striking, the paper’s senior author Adam Boies, a professor of nanomaterials and aerosol engineering at the University of Cambridge, said it’s the similarities they found between tobacco and cannabis smoke that should interest the public. The study team found that tobacco and cannabis smoke particles are very similar in terms of their volatility, shape, density and concentration.
“We should think about it [cannabis smoke] largely in the same context as tobacco smoke, or any other particle-based pollution,” said Boies. “Unless we have some very strong evidence to indicate otherwise, I think we should largely treat all smoke roughly the same.”
How all of this amounts to a health threat is still under investigation. Historically, the legal status of the drug has made large trials challenging, and the nature of cannabis use makes it tricky to study it precisely: For example, a pack of cigarettes is precisely regulated and makes dosage easy to know compared to the more imprecise nature of a joint. People are often exposed to more tobacco smoke than cannabis smoke, and users tend to indulge in both at the same time. This makes it challenging to study the health of a smoker, let alone a person exposed to secondhand smoke.
Animal studies suggest persistent exposure to cannabis smoke can come with a cost. A study on rats, for example, found that the particulate matter in cannabis smoke can cause lung irritation and respiratory infections. It also caused the dilation of blood vessels and decreased blood pressure, which could harm heart health. Studies on cannabis users suggest an increased risk for cough and wheezing, bronchitis and changes in lung function.
Others argue for a common sense approach to interpreting how safe secondhand cannabis smoke is.
“There may be chemical differences between wildfire smoke, secondhand smoke, diesel smoke, and cannabis smoke, but they all are very chemically [reactive] particles,” said Schick. “And they are all bad for your blood vessels, and really increase your risk of strokes, heart attacks and all kinds of casual diseases at very low concentrations.”
Perceptions of cannabis and why they matter
Because cannabis is increasingly legal and consumed publicly, people are being exposed to it more, Cohen said. This might explain why people are noticing the smell more often, she observed.
Cohen suspects that part of the reason it’s perceived as safer than tobacco is that we’re still in the early days of scientific research, and the public health messaging surrounding it is very minimal compared to cigarette smoke.
“If you look at our data on risk perceptions, and data on use, people are perceiving it as less risky and they are using it more,” Cohen said.
This takeaway is backed Cohen’s study from August — which involved the responses of 5,035 US adults who were surveyed in 2017, 2020 and 2021. They were asked about how safe they considered cannabis smoke versus tobacco smoke in regards to daily smoking and secondhand exposure.
The responses show an increasingly positive viewpoint of cannabis smoke over time: In 2017, approximately 37% viewed cannabis smoke as safer. By 2021, this jumped to 44%.
Cohen also observed that cannabis regulation is less restrictive than that of tobacco, and some smoke-free laws are being amended to allow cannabis smoking or vaping.
One of Boies’ takeaways from his own research is that the findings suggest a sensible adjustment to consuming cannabis in a way that doesn’t involve smoke.
“If one really wants to avoid this but yet wants to participate in cannabis use, there are other forms that are probably better,” Boies said. “Better both for the individual and for those around. I think there’s a growing consciousness of the air we breathe and that it’s this shared resource.”
(Except for the headline, this story has not been edited by PostX News and is published from a syndicated feed.)