As America debates drug policy reforms and marijuana legalization, there's one aspect of the war on drugs that remains perplexingly contradictory: Some of the most dangerous drugs in the US are legal.

Don't believe it? The best available data from the Centers for Disease Control and Prevention (CDC), Drug Enforcement Administration (DEA), and National Institute on Drug Abuse (NIDA) shows tobacco, alcohol, and opioid painkillers were responsible for more direct deaths in one year than any other drug. This chart compares those drug deaths with the best available data for cocaine, heroin, and marijuana deaths:

Now, this chart isn't a perfect comparison across the board. One driver of tobacco and alcohol deaths is that both substances are legal and easily available. Other substances would likely be far deadlier if they were as available as tobacco and alcohol. And federal data excludes some deaths, such as drugged driving deaths, which is why the chart focuses on direct health complications for all drugs.

Deaths also aren't the only way to compare drugs' harms. Some drugs, such as alcohol and cocaine, may induce dangerous behavior that makes someone more predisposed to violence or crime. Other drugs, like psychedelics, may trigger underlying mental health problems or psychotic episodes. When evaluating the overall harm caused by drugs, all of these factors should be taken into account.

But the high total number of deaths is still a major concern for public health policy. And according to experts and researchers, lawmakers could do more to curb deaths caused by the three deadliest drugs — if only they paid more attention to legal drug policy.

1) Tobacco

When it comes to deadliness, no single substance comes close to tobacco. To put its risk in perspective, more Americans die from tobacco-caused health problems like lung cancer and heart disease than from reported drug overdoses, car crashes, and homicides combined.

The chart at the top of this article actually understates the number of tobacco deaths, since it only considers the most direct causes of deaths and excludes secondhand smoking, perinatal conditions, and residential fires.

Overall, cigarette smoking is linked to one in five deaths in the US each year, according to CDC estimates for average annual fatalities based on deaths between 2005 and 2009. Nearly 42,000 of the total 480,000 deaths from smoking are caused by secondhand smoke.

US tobacco use has greatly declined in the past several decades, although nearly one in six high school students and adults still smoked cigarettes in 2013 and 2014. Experts attribute the decline to various factors, including education campaigns, mandatory warning labels, public and workplace smoking bans, and higher taxes on tobacco products. Continuing these efforts, public health officials hope, will continue pushing down the rate of smoking in the US. But states could also take additional steps, like increasing the smoking age.

2) Alcohol

Alcohol-induced health problems, such as liver disease, led to more than 33,000 deaths in 2015. But that actually undercounts the number of deaths caused by alcohol: When including other causes of death like drunk driving and homicides, the toll rises to 88,000 per year. (This number might be an undercount too, since it's an estimate for 2006 to 2010 and alcohol-linked deaths have steadily risen over the past several years.)

The death toll may understate the more general risk of alcohol. A 2010 analysis, led by British researcher David Nutt and published in The Lancet, took a comprehensive look at 20 of the world's most popular drugs and the risks they pose in the UK. A conference of drug experts measured all the factors involved — mortality, other physical damage, chance of developing dependence, impairment of mental function, effect on crime, and so on — and assigned each drug a score. They concluded alcohol is by far the most dangerous drug to society as a whole.

What makes alcohol so dangerous? The health effects of excessive drinking and drunk driving are two obvious problems. But there are other major issues rooted in alcohol-induced aggression and erratic behavior: injuries, economic productivity costs, family adversities, and crime. (Alcohol is a factor in 40 percent of violent crimes, according to the National Council on Alcoholism and Drug Dependence.)

Still, The Lancet's report has come under some major criticisms. Although drug policy experts generally agree that alcohol is dangerous — and definitely more dangerous than marijuana — they argue the report misses some of the nuance behind each drug's harms. For one, it doesn't entirely control for the availability of these drugs, so it's possible heroin and crack cocaine in particular would be ranked higher if they were as readily available as alcohol. And the findings are based on the UK, so the specific scores would likely differ to some extent for the US — particularly for meth, which is more widely available in the states.

Alcohol is definitely more dangerous than marijuana

To show the Nutt analysis's flaws, Jon Caulkins, a drug policy expert at Carnegie Mellon University, gave the example of an alien race visiting Earth and asking which land animal is the biggest. If the question is about weight, the African elephant is the biggest land animal. But if it's about height, the giraffe is the biggest. And if the question is about length, the reticulated python is the biggest.

"You can always create some composite, but composites are fraught with problems," Caulkins said. "I think it's more misleading than useful."

The blunt measures of drug harms present similar issues. Alcohol, tobacco, and opioid painkillers are likely deadlier than other drugs because they are legal, so comparing their aggregate effects to illegal drugs is difficult. Some drugs are very harmful to individuals, but they're so rarely used that they may not be a major public health threat. A few drugs pose more short-term than long-term risks through overdose (heroin), while others are more dangerous in the long term due to chronic health problems (tobacco). And looking at deaths or other harms caused by certain drugs doesn't always account for substances, such as prescription medications, that are often mixed with others, making them more deadly or harmful than they would be alone.

Still, experts acknowledge, it's clear alcohol is dangerous and deadly. To curb the deaths and risks linked to alcohol, they often suggest tighter regulations, higher taxes, more education, and even taking away some people's right to drink.

A previous analysis by the RAND Corporation found that states that sold alcohol through tightly regulated, state-run establishments kept prices higher, reduced access for youth, and decreased drinking overall. Studies show that higher alcohol taxes could reduce consumption and, as a result, the problems the drug causes. And the 24/7 Sobriety Program, which effectively revokes people's right to drink if their drinking gets them in trouble with the law, has been linked to decreases in mortality, DUI arrests, and domestic violence arrests.

3) Opioid painkillers

Highly addictive opioid painkillers are now part of a national epidemic of overdose deaths.

In the 1990s, drug companies, such as Purdue Pharma, pushed opioid painkillers on doctors and patients through an aggressive, misleading marketing campaign. Doctors, who were under pressure from advocates and government agencies to treat pain as a serious medical issue, prescribed the drugs in huge droves, letting them proliferate — not just to patients, but to the patients' family and friends and the black market. As a result, opioid painkiller deaths skyrocketed.

Opioid overdose deaths sometimes involve multiple drugs. Benzodiazepines and alcohol, for instance, can increase the risk of an opioid overdose. But without opioids, these deaths may have been avoided entirely.

Policymakers have responded to the rise in deaths by putting tighter restrictions on the distribution of opioid painkillers and cracking down on "pill mills," which are doctors, clinics, and pharmacies that dispense opioid painkillers unscrupulously or for nonmedical reasons.

In part as a response to the crackdown, some opioid users turned to other opioids that are more potent and potentially more easily accessible — notably, heroin and fentanyl. For public health officials, this has emphasized the need to increase prevention and treatment programs, particularly medication-assisted treatments such as methadone and Suboxone, to try to get people off opioids for good. After all, unless people overcome their addiction, cuts in the supply are only going to lead people to try to get their fix somewhere else.

There's also concerns that restricting painkillers too much makes it more difficult for people to get the medicine they genuinely need for chronic, debilitating pain. A 2011 report from the Institute of Medicine found that many Americans are undertreated for acute and chronic pain. And multiple reports suggest doctors have avoided working in chronic pain treatment because the legal and regulatory hurdles are so big. (Still, the evidence on whether opioid painkillers can even treat chronic pain is weak at best, even as it's clear that prolonged use can result in very bad risks and complications.)

One way to fill this need for treatment without resorting to dangerous opioids may be medical marijuana. Several studies have found that states that allow pot for medicinal purposes — particularly states that allow dispensaries, where marijuana is sold — have fewer prescription painkiller deaths than one would otherwise expect. Intuitively, this makes sense: Marijuana is a potent painkiller for some types of pain, so it can potentially substitute deadlier and more addictive opioids in some cases.

Still, while marijuana may work for some patients, it may not for many others. This leaves opioid painkillers as one of the few medications for some pain patients, which requires doctors and regulators to balance out patients' needs with the risk these addictive, deadly drugs present.

What about illicit drugs?

There's admittedly no good federal mortality data on the less direct and long-term impacts of illicit drug use. But there's reason to think the scale of overall deadliness in the chart at the top of this article wouldn't change much with additional data.

The deadliness of the harder drugs, like crack and cocaine, is severely limited in part because very few people use such substances, especially in the long term. About 0.1 percent of the US population 12 and older reported using heroin and roughly 0.7 percent reported using cocaine in the previous month, according to a 2015 federal survey. (This could change if the illicit drugs were legal and more accessible.)

Still, these harder drugs are dangerous. Cocaine and crack can lead to heart attack and stroke, and they can cause violent behaviors that make someone more prone to crime. And heroin poses a massive risk of deadly overdose — a risk that only gets worse as someone uses heroin more and more.

"The main risk of cannabis is losing control of your cannabis intake"

Marijuana is more widely used, but it's never been definitively linked to direct deaths or even other medical conditions. The most thorough review of the research yet, from the National Academies of Sciences, Engineering, and Medicine, found that pot poses a variety of possible downsides — including respiratory problems if smoked, schizophrenia and psychosis, car crashes, general social achievement in life, and potentially babies in the womb.

But pot doesn't appear to pose a high risk, if any, of deadliness (outside of car crashes and other accidental deaths). The research review found smoking pot doesn't even seem to cause some of the major health problems that are typically linked to tobacco, particularly lung cancer and head and neck cancers.

And the studies reviewed also suggest marijuana carries several benefits, particularly for chronic pain, multiple sclerosis, and chemotherapy-induced nausea and vomiting. (There wasn't enough research to gauge if pot is truly good for some of the other ailments people say it's good for, such as epilepsy and irritable bowel syndrome.)

Still, there's another, more abstract risk to pot: dependence.

"The main risk of cannabis is losing control of your cannabis intake," Mark Kleiman, a drug policy expert at New York University's Marron Institute, previously told me. "That's going to have consequences in terms of the amount of time you spend not fully functional. When that's hours per day times years, that's bad."

Caulkins of Carnegie Mellon University put it another way: "At some level, we know that spending more than half of your waking hours intoxicated for years and years on end is not increasing the likelihood that you'll win a Pulitzer Prize or discover the cure for cancer."

So a drug's deadliness isn't everything we need to know about its harms. But deadliness is still a powerful measure — and it suggests that the public and policymakers shouldn't assume that a substance is more dangerous to society as a whole just because it's illegal. In fact, based on the numbers, it's legal drugs that may require more policy attention.