Smoking Cannabis and Cancer

Walk into a California dispensary and prominently displayed at eye level is likely a sign that reads, “Smoke from cannabis contains chemicals known to the state of California to cause cancer. State of California Prop 65 warning.”

Most young people probably don’t read the sign. But imagine the arthritic 75 year old visiting a dispensary for the first time who wants to try cannabis as an alternative to her daily cocktail of pharmaceutical pills and their laundry list of side effects. She most likely reads the sign.

Recently, I visited Buds and Roses, a Prop D compliant dispensary in Los Angeles, California. As I entered the dispensary, the warning sign was displayed on the door between the reception area and the dispensary retail space.

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I asked Aaron Justis, president of Buds and Roses, about the sign. He mentioned that recently several dispensaries across California were served 60 day notices for not being Prop 65 compliant. As a result of the subsequent legal case, all dispensaries in California that have 10 or more employees are now required to prominently display Prop 65 signage in the dispensary.

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Prop 65 is a list of chemicals that, according to California’s Office of Environmental Health Hazard Assessment (OEHHA), are known to cause cancer, birth defects, or other reproductive harm.

The Office of Environmental Health Hazard Assessment is the scientific arm of the California Environmental Protection Agency. Our mission is to protect public health and the environment by scientific evaluation of the risks posed by hazardous substances.

For example, when you buy a new car, there’s a sticker on the driver’s side window that states:

WARNING: Automobiles, and the components, replacement parts and maintenance thereof, contain chemicals known to the State of California to cause cancer, birth defects, and other reproductive harm. Posted under California Prop. 65 Health and Safety code 2524935. Additional details regarding Prop 65 may be found at

The OEHHA is the agency that controls which chemicals are added to the Prop 65 list. Once a chemical is on the list, companies that sell products that contain that chemical are required to provide a warning to customers.

However, I later learned that there is no common sense process through which the OEHHA informs companies that sell products which contain a Prop 65 chemical, in this case dispensaries and cannabis, that they need to comply with Prop 65 law and what constitutes compliance.

When a new chemical is added to the Prop 65 list, a list that has ballooned to almost 900 chemicals, OEHHA needs to publish a notice in the California Regulatory Notice Register. Who reads that? Nobody. They also post all of their notices on the OEHHA web site – also not a well trafficked source of public information. From their perspective they’ve done all they need to do. You as a business need an advocate for your industry to check to see how your industry might be affected by the almost weekly addition of new chemicals.

Confused, I went home from my visit to Buds & Roses and googled “Prop 65 and cannabis”.

I found a 2009 OEHHA report which recommends adding cannabis to the Prop 65 list of cancer causing chemicals. However, when I started to read the report, I discovered that it was really a meta-study that cites research conducted by others.

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One of the names cited several times in the OEHHA report is Dr. Donald Tashkin, a pulmonary expert from UCLA who has done extensive (40 years) government funded research on cannabis and lung cancer. Familiar with Donald Tashkin, I know that his research comes to the exact opposite conclusion – smoking cannabis not only doesn’t cause lung cancer, but it might in fact reduce the possibility of developing lung cancer. So I picked up the phone and called him up.

Dr. Tashkin confirmed that his research does not conclude that smoking cannabis causes cancer. As he said in our call, “The weight of evidence is against marijuana use (in the absence of tobacco) as a cause or predisposing factor for lung cancer.” He later added, “the fact that an agent is carcinogenic doesn’t mean that in real life it will cause cancer. Yes, there are carcinogens in Marijuana smoke. But that doesn’t necessarily translate into the actual risk for developing lung cancer. So what you have to take into account is that there are modifying factors that counteract the carcinogens of marijuana smoke. There are scores of studies showing that THC specifically, in cell culture systems and in experimental animal models, does suppress tumor growth. These tumor inhibiting effects of THC apparently counterbalance the pro-carcinogenic effects of the carcinogens tar in marijuana smoke. So you can’t say that just because the substance has carcinogens in it that it will necessarily lead to cancer.”

My layman’s translation is that you have to look at the net effect of the negative and positive chemicals inhaled and, according to Dr. Tashkin, the net effect is a possible statistical decrease in instances of lung cancer for marijuana smokers compared to those who don’t smoke anything.

That is a crazy and unexpected conclusion, but one that seems to be corroborated by the growing body of scientific evidence. That doesn’t mean that there might not be healthier ways to consume cannabis, such as through a vaporizer or by eating edibles, because there are other adverse effects related to smoking flower, like pulmonary inflammation, but that’s not cancer, which is the mandate of the OEHHA Prop 65 list.

He also confirmed that no one from the OEHHA ever contacted him, despite their citing his research numerous times in the final OEHHA report that recommends adding cannabis to the Prop 65 list. That kind of surprised me. Google Dr. Donald Tashkin. His UCLA affiliation and contact information are readily available online for anyone who is inclined to talk to him.

Another research study referenced in the OEHHA report was a 2008 study, “Cannabis use and risk of lung cancer: a case control study“. A response to this research study came from Marek Chawarski, PhD, Associate Professor of Psychiatry and of Emergency Medicine, Yale University School of Medicine. Dr. Chawarski wrote a letter to the Editors of the European Respiratory Journal concerning his evaluation of the study, which asserts that they have strong evidence supporting a claim that “long-term cannabis use increases the risk of lung cancer in young adults”.  In his opinion, their evidence was not as strong as purported.

In the letter to the Editors, signed by Dr. Chawarski, along with Dr. Richard Andrew Sewell, a member of the Neuropsychopharmacology Research Group at Yale University, the authors argue, “the conclusion stating that ‘‘long-term cannabis use increases the risk of lung cancer in young adults’’ is inadequately supported by the data, given the study’s several methodological flaws.”

In an email to me, Dr. Jonathan Cachat, PhD, who was responsible for developing strategies and programs for the collection, description, organization, normalization, storage, preservation, integration, visualization and mining of data across the spectrum of neuroscience programs at UC Davis, states:

Chawarski challenges the statistical power of their study, which is valid due to their reliance on linear regression models to establish correlations, not casualty. 

Another way to think about this – in Beasley’s study there were “79 cases of lung cancer and 324 controls” – 79 people with lung cancer and 324 people without. In order to confidently state there is a relationship, Chawarksi calculated that the sample sizes would need to be 12,000 people with lung cancer and 50,000 controls. More data = more powerful predictive power. 

The second call out is great – more than half of his subjects were 50-55, yet referred to as young adults – this is a great, subtle indicator of biases or agenda in the narrative. 

In my opinion/critique – Adlington…Beasley (2008) was a sociological (observational as Chawarksi says) study. People tend to bend the truth on self reports of illegal behavior. If we want to understand the relationship of cannabis with cancer, we need to study cannabinoids at a molecular level – a majority of those studies show anti-cancer effects. the only caveat I am aware of is if the tumor does not have cannabinoid receptors, then phytocannabinoid treatment will not be effective. 

Digging a little deeper, we discovered that the same research group in New Zealand, The Cannabis and Respiratory Disease Research Group of New Zealand, published a 2015 study that contradicts their 2008 study. In the 2015 paper, they conclude, “Results from our pooled analyses provide little evidence for an increased risk of lung cancer among habitual or long-term cannabis smokers, although the possibility of potential adverse effect for heavy consumption cannot be excluded.”

I sent multiple emails to Brian Cox, the common author from both studies (2008 and 2015), to confirm that the two reports come to different conclusions, and am still waiting to hear back.

I also reached out to Rajpal Tomer, one of the authors of the OEHHA report, to ask about the OEHHA’s research process and whether it includes common sense practices such as talking to anyone involved in the research they cite as the basis for their recommendations, but never heard back.

I then moved on to the legal side of the issue. Twenty eight dispensaries across California were served 60 day notices, which formally starts the legal process for Prop 65 violations, by one plaintiff (Michael DiPirro), and another ten dispensaries were served 60 day notices by another plaintiff (Tyanna Walker).

I contacted the law firm that represented eight dispensaries, including Buds & Roses, that banded together in the Prop 65 case to share the legal costs. Many others hired their own attorneys.

Through my conversations with one of the lawyers at Wykowski Law, which represented the eight dispensaries, I learned that David Bush (along with his partner Jennifer Henry) was the lawyer who brought a private attorney general action against the dispensaries.

Private attorney general is an informal term usually used today in the United States to refer to a private attorney who brings a lawsuit considered to be in the public interest, i.e., benefiting the general public and not just the plaintiff, on behalf of a citizen or group of citizens. The attorney is considered a “private attorney general” and may, at the equitable discretion of the court, be entitled to recover attorney’s fees if he or she prevails. The rationale behind this principle is to provide extra incentive to private attorneys to pursue suits that may be of benefit to society at large.

Prop 65 is a well intentioned statute but, like many statutes, has been abused.

With a little research, I discovered that David Bush and partner Jennifer Henry, along with super plaintiff Michael DiPirro, have a long history of initiating private attorney general actions against companies across a variety of industries for non-compliance with Prop 65.

Here’s the team of Bush, Henry and DiPirro sending a 60 day Prop 65 violation notice to a garden hose maker, a tent maker, and a power tool rental company way back in 2001. DiPirro has been the plaintiff in cases dating as far back as 1997. There aren’t PDFs in the Office of the Attorney General database that go that far back, so it’s unclear whether Henry and Bush were the lawyers representing the plaintiff in those cases. The search results on the Prop 65 database show 36 pages (20 search results per page) of Michael DiPirro as the plaintiff in Prop 65 cases. Either this guy really really cares about the public good, or he really cares about the payout from suing companies across pretty much every industry imaginable.

Bush went after a beer pong / drinking game company with DiPirro, and after a cosmetics company, and a ceramic mug maker with other plaintiffs .

Henry seems especially vigilant fighting for the public good, going after a book publisher for failure to warn, a tow rope maker, a bracelet maker, a pocket notebook maker, a toiletry bag maker, a beauty company, an LED flashlight maker, a tote bag maker, a rain coat maker, a calendar maker, another bag manufacturer and…well, you get the point. It seems that she mastered the craft while working for notorious Prop 65 abuser Cliff Chanler.

Prop 65 cases are difficult to defend, so the plaintiff Michael DiPirro, represented by David Bush and Jennifer Henry, is likely to win. And part of “winning” is a payout to the attorney who initiates the action, which includes reimbursement for hourly fees along with a percentage of the penalty assessed. Lawyers who initiate Prop 65 cases get fees for doing little work and knowing there are very few defenses for the defendants. They can become professional plaintiffs and build a nice little income stream from litigating such cases., which are often settled quickly without going to court.

Some, myself included, might call the Henry / Bush team Prop 65 chasers, building their practice by finding companies to sue for Prop 65 non-compliance. Ironically, on his Linkedin page, David Bush positions himself as a cannabis lawyer, ready for hire, evidently, by your cannabis business. In fact, you can check out his advertising on his facebook page where, ironically, he references his work with the Willie Nelson Peace Research Institute.

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I wonder if he lectures Willie about the cancer risks associated with smoking cannabis? Willie, by the way, is a spry 82, showing no ill effects of his well documented long term smoking habit.

My next step is to reach out to all the scientists whose research was cited in the OEHHA report as well as people in the scientific community to evaluate the data and methodologies used in some of those primary research studies.

I also want to finally talk to someone at the OEHHA. I have a laundry list of questions.

What was the process through which cannabis was recommended to the OEHHA as a potential carcinogen, worthy of review to ultimately be added to the Prop 65 list? More specifically, who recommended to the OEHHA that cannabis be explored as a potential addition to the Prop 65 list? Did the OEHHA ever reach out to any of the study authors they reference in their recommendation report? How many chemicals have been nominated for inclusion but didn’t make it onto the Prop 65 list? Does the OEHHA periodically review current science related to chemicals previously added to the Prop 65 list? What is the appeals process for removing a chemical from the Prop 65 list? How does the OEHHA alert, if at all, affected businesses that a new “chemical” has been added to the list and their respective responsibilities to warn customers?

Mostly, I’d like to know whether cannabis is on the Prop 65 list based on science or politics?

The ultimate goal is to re-evaluate the scientific evidence regarding a possible link between cannabis and cancer. There is a wealth of scientific studies conducted in the past ten years on the topic. If the research points in the opposite direction, towards no link or even reduced cancer risk, what is the recourse for those who want to petition the OEHHA to re-evaluate and potentially remove cannabis from the prop 65 list?

From my conversation with a Proposition 65 attorney, if there are enough people interested in having marijuana smoke delisted, with the support of scientists, we can file a petition with the OEHHA with the scientific arguments as to why marijuana should be delisted. The petition can’t just be that there are benefits to smoking marijuana, it has to attack the carcinogenicity of marijuana smoke.

The OEHHA will most likely say no, and deny the request. But that negative response will give us standing, the right to sue the OEHHA for failure to follow its own rules for what it takes to list or not list a chemical. In short, the OEHHA’s negative response to the petition would form the basis of a lawsuit against the agency. 

As for attacking the 2009 listing itself, a court will likely consider the 2009 listing decision too old to challenge. The statute of limitations to sue on the listing decision may be considered to have passed. But a denial of a petition would form a timely basis on which to challenge OEHHA’s identification of cannabis smoke as a carcinogen.

 Want to get involved? You can reach me @ peter AT futurecannabisproject DOT org