People often ask about the possible psychoactive effect of exposure to secondhand marijuana smoke and whether a person who has inhaled secondhand. The impairments in brain connectivity associated with exposure to marijuana in . arterial blood vessels) and the indirect effects on vasoactive compounds may. There is evidence of a direct relation between the tetrahydrocannabinol content of marijuana and effects on those passively exposed.
Cannabis Exposure Effects of Indirect
Exposure to second-hand marijuana smoke leads to cannabinoid metabolites in bodily fluids, and people experience psychoactive effects after such exposure. Alignment of tobacco and marijuana smoking bylaws may result in the most effective public policies. More research is required to understand the impact of exposure to third-hand smoke and the health effects of long-term exposure to second-hand smoke. A nationally representative Canadian study showed that Effects of passive exposure to tobacco smoke, including both second- and third-hand smoke, have been reported.
In jurisdictions where marijuana remains an illegal substance, it is difficult to impose regulations or health warnings to try to limit exposure to second- and third-hand smoke, which raises concerns for public health. In the last 5 years, recreational marijuana has been legalized in 6 jurisdictions: In November , 5 additional US states voted on proposals to legalize marijuana; the proposals passed in Nevada, California, Maine and Massachusetts, and failed in Arizona.
Canada plans to legalize marijuana in , and it is likely that more US states and jurisdictions will legalize the drug in the coming years. With this changing landscape, there is a need to better understand the public and individual health risks associated with exposure to second- and third-hand marijuana smoke.
The objective of this work was to synthesize the available evidence on this topic. This information will be important to support evidence-informed policy and to support patient-care provider conversations to reduce harm. A library and information specialist developed the search strategies. We conducted the search using all MeSH terms referring to marijuana e.
Abstract review was conducted independently by 2 reviewers H. To be included, studies had to be human, in vivo or in vitro studies with more than 1 case reported in English or French, and report original, quantitative data.
Abstracts were excluded if they failed to meet all the inclusion criteria; thus, all case reports, commentaries, editorials and letters were excluded.
Studies included by either reviewer proceeded to full-text review, which was also conducted by 2 independent reviewers H. Any disagreements between reviewers were resolved through discussion of the full text; if required, a third reviewer F. After full-text review, the reference lists of included studies were searched to ensure no relevant studies were overlooked.
Data extraction was performed by 2 reviewers H. We assessed the quality of the included studies in duplicate using the Downs and Black checklist, a item checklist for assessing the methodological quality of both randomized and nonrandomized studies of health care interventions.
We categorized records as studies that measured the chemical components of marijuana smoke or those that investigated the immediate effects on people exposed to second- or third-hand marijuana smoke.
Based on outcomes reported, the studies that investigated the immediate effects of exposure were further categorized into 3 subcategories: We synthesized the findings within each category qualitatively.
Synthesis involved reporting aspects of the findings that were similar or, if there were discrepancies between studies, reporting the differences in study design, methods or execution that could account for the differences.
We identified unique abstracts. Of these, 60 proceeded to full-text review, 15 of which were included in the final data set Figure 1.
The 15 records reported findings from 8 unique studies. All 15 records were experimental studies on the immediate effects of marijuana smoke exposure in humans in a controlled environment. They all followed a similar protocol whereby nonsmokers sat in proximity to people who were actively smoking. Physiological or psychological outcomes were measured after a period of exposure.
All included studies assessed short-term within 24 h of exposure effects of smoke exposure; none assessed health effects beyond 24 hours.
Meta-analysis was not possible owing to heterogeneous outcomes and reporting, and, therefore, the included studies were synthesized narratively.
All of the included studies were of good to poor quality. The average score on quality assessment was Oral fluid concentrations of THC were reported in 4 reports from 3 studies. Blood concentrations of THC were measured in 8 reports from 6 studies. In 13 reports from 9 studies, the investigators assessed THC metabolite concentrations in urine samples.
Urine levels of tetrahydrocannabinol THC and metabolites and subjective effects in participants passively exposed to marijuana smoke in an unventilated environment, hours after exposure, by THC content. In 2 studies, multiple trials were conducted in ventilated and unventilated environments. Other factors that mediated the effects of exposure to second-hand smoke included air volume, number of participants inhaling second-hand smoke, THC content, number of marijuana cigarettes lit and number of active smokers.
In 2 studies, the psychoactive effects reported by participants exposed to second-hand smoke were described. In 1 study, participants exposed to second-hand smoke reported discomfort and eye irritation due to smoke in the room. Second-hand exposure to marijuana smoke can lead to cannabinoid metabolites in bodily fluids sufficient for positive results on testing of oral fluids, blood and urine, and can lead to psychoactive effects.
There is evidence of a weak dose-response relation between THC content of cannabis and effects on those exposed to second-hand smoke, including metabolites found in blood and urine, and psychoactive effects. There is evidence that the relation is mediated by environmental factors, including whether the air space is ventilated, volume of air, number of marijuana cigarettes lit at 1 time, potency of the marijuana and number of smokers.
The simulated environments within some of the included studies may not represent "real-world" scenarios. Some studies placed participants in simulated environments where they were exposed to smoke in closed rooms with controlled ventilation systems.
In the context of legalization, people may be exposed to second-hand marijuana smoke outside, in parks or in passing on the sidewalk. This type of exposure may not result in cannabinoid metabolites in bodily fluids, as the exposure may be shorter and less intense than in unventilated areas.
In addition, exposure in unventilated spaces such as vehicles or small rooms in private homes is still likely to occur. Thus, the observed relation between second-hand smoke exposure and cannabinoid metabolites in bodily fluids is likely to be generalizable to real-world contexts. Marijuana use in enclosed spaces, particularly in the presence of children, older people or people with respiratory illness, should be limited, ideally through public health measures and legislation in jurisdictions where marijuana is legalized.
In some domains, mirroring public health legislation to protect workers and the general public from second-hand tobacco exposure will be appropriate. For example, bylaws forbidding smoking in indoor spaces such as bars and nightclubs and in shared outdoor spaces such as beaches or parks should be considered. Tobacco smoking frameworks may be useful to inform control regulation. Alignment of tobacco and marijuana smoking bylaws, with a coherent policy approach to exposure to smoke of any kind, may result in the most effective public policies.
Evidence suggests that the chemical composition of second-hand marijuana smoke is similar to that of second-hand tobacco smoke, although differences in the concentrations of the components vary. Using levels of cannabinoid or THC metabolites found in blood or urine samples to determine marijuana use or intoxication is challenging.
There is no universal threshold that can differentiate between those who have actively smoked marijuana and are intoxicated, those who have actively smoked marijuana in the past and those who have been exposed to second-hand smoke.
In many jurisdictions that have adopted thresholds for THC for drivers, 5. This raises questions about whether there should be tolerance for people who claim that their positive urine test result is due to second-hand exposure. As more jurisdictions legalize marijuana for recreational use, smokers may feel that use in common public areas or around children is acceptable, and, subsequently, harms associated with second-hand exposure may also increase.
In the current state of the literature on second-hand exposure to marijuana smoke, it is difficult for clinicians to prepare to engage with patients in thorough assessments of marijuana exposure as they would with tobacco and for policy-makers to make evidence-based decisions. Future research to inform the development of effective communication tools, prevention strategies and policies to minimize harms to individual users and society is required.
Our systematic review did not identify any studies reporting the long-term effects of exposure to second-hand marijuana smoke or the effects of exposure to third-hand smoke. Participants were not followed beyond the experiment, and it is not known how repeated exposure to marijuana smoke may affect health.
Given the known harms associated with active marijuana use, such as mental illness, brain developmental changes, respiratory and cardiac disease, and poor prenatal outcomes, 2 , 38 the long-term impact of passive exposure requires further study. In the absence of evidence, based on the learnings from tobacco, a focus on harm reduction and limiting passive exposure may be prudent.
One limit of our search strategy is that studies that were not in English or French were excluded, and the included studies were conducted primarily in anglophone countries.
Furthermore, the included records are limited in transferability owing to small samples and the homogeneity of the population studied. The included studies were of good, fair or poor quality; no excellent studies were identified. The addition of excellent-quality studies may have improved the robustness of our findings.
The body of literature assessing exposure to second-hand marijuana smoke uses an experimental study design that may not be generalizable more broadly.
However, it is likely that, under some regulatory conditions, people will be exposed in ways similar to those of the trials, which would enhance the generalizability of the findings to the real world.
Exposure would likely be longer and more frequent if people were visiting a location where marijuana smoke was present, and, therefore, the generalizability of the results may be somewhat limited. Tetrahydrocannabinol metabolites are retained in the body upward of 4 hours, and people report the experience of psychoactive effects after exposure to second-hand smoke. On a molecular level, marijuana smoke has chemical components similar to those of tobacco smoke, although they are present in different amounts.
Although this provides support for the biological plausibility of the relation between exposure to second-hand marijuana smoke and negative health outcomes, there is a gap in the literature in this area. If exposure to second-hand marijuana smoke has similar health risks as direct marijuana use, it may be associated with conditions such as respiratory and cardiac disease as well as mental illness.
However, high-quality research on the long- and short-term health effects of exposure to second-hand marijuana smoke are required to confirm these possible risks. Given the current state of knowledge, coherent policy approaches to exposure to smoke of any kind may result in the most effective harm-reduction policy. For reviewer comments and the original submission of this manuscript, please see www.
The authors extend special thanks to Rebecca Saah of the University of Calgary for her help and critical comment on early drafts. Studies show that when you are around someone who is smoking marijuana, the smoke gets into your system too. How much of it gets in depends on how close the person is, how many people are smoking and how much, how long you spend near them, and how much ventilation there is in the space.
With more and more states legalizing marijuana for recreational use, that number is likely to continue going up. This is not good.
While research is still ongoing , there is evidence to suggest that when youth and young adults whose brains are still developing are exposed to marijuana, it may have permanent effects on executive function , memory, and even IQ. All the advice we give to parents who smoke tobacco applies to parents who smoke marijuana, including:.
What, if anything, can be done about neighbors who smoke? She has two very young children and is rightfully concerned. Is smoking really that important? I have a question about a mother who smokes marijuana and breastfeeds.
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The long-term effects of cannabis have been the subject of ongoing debate. Because cannabis . In the general population a weak (indirect) association appears to exist between suicidal behaviour and A literature review said that exposure to cannabis was "associated with diseases of the liver (particularly with. Marijuana smoking around children under 18 has increased and is likely exposed to marijuana, it may have permanent effects on executive. Concentrated exposure to marijuana smoke can cause range of detectable effects for nonsmokers, researchers find.