When people talk about “killer weed,” that’s typically understood to mean really good weed. But due to US government policies that started in the 1970s and extended through most of the 1980s, marijuana fields were being sprayed with a chemical that can actually kill you.

The chemical, known as “paraquat,” is an herbicide sprayed over marijuana fields in Mexico in the 1970s—with the aid of US money and US-provided helicopters—and over marijuana fields in Georgia in the 1980s under the direction of the Reagan Administration.

But normally, anything poisonous enough to kill plants is also toxic enough to kill humans, and that is the case with paraquat.

What is paraquat and how can it harm humans?

• Paraquat is an organic acid that is used as an herbicide. It kills green plant tissue on contact.

• When sprayed on plants, paraquat is tasteless and odorless and invisible. In other words, you wouldn’t be able to tell if the weed you were smoking had been sprayed with paraquat.

• As far as breathable poisons go, the government has placed paraquat in Toxicity Category I—the highest possible level.

• Due to the fact that it is cheap and available, liquid paraquat is frequently used in suicides throughout much of the Third World.

• In humans, exposure to paraquat has been linked to the development of Parkin’s disease.

• Depending on the dose and the method of ingestion, paraquat can either be immediately fatal or can lead to kidney, liver, lung, and heart failure for up to 30 days after exposure.

• Tests performed in 1977 demonstrated that combusted paraquat caused damage to the lungs of laboratory rats.

• In 1978, after years of attempting to reassure Americans that smoking paraquat-tainted marijuana was safe, US Secretary of Health Education and Welfare Joseph Califano announced that new tests found that heavy smokers of tainted weed could develop irreversible lung damage and that even moderate users could develop “clinically measurable damage.”

1970s: Paraquat Pot From Mexico Comes To The USA

In 1969, the Nixon White House made marijuana eradication a top priority. Rather than attempting to stop the flow of drugs in through the border, scientists began looking for a way to directly contaminate the marijuana itself. They originally developed a spray that was intended to make users nauseous, but this was shelved.

In 1975, as part of “Operation Clearview,” the Nixon Administration started supplying Mexico with about $15 million annually in aid that included helicopters designed to spray marijuana and poppy fields with herbicides.

Officials had recommended spraying marijuana fields with herbicides—their stated intent was to kill the drug at its source by spraying the fields. But in deeply impoverished Mexico, where in the 1970s harvesting marijuana could make the difference between a yearly income of $200 and one of $5,000, many growers simply harvested the poisoned marijuana and shipped it north anyway.

According to one report, an American helicopter pilot was getting high on prime Oaxacan weed while he was spraying fields below him with paraquat.

According to one study in 1978, 13 percent of marijuana samples texted in the southwestern USA were contaminated with paraquat. Other tests found that anywhere from 20 to 30 percent of the marijuana that had made its way into the US from Mexico was paraquat-tainted. Some samples contained concentrations of paraquat that were 40,000 times higher than the recommended domestic use.

This led to a public panic, seeing as how marijuana may have been even more popular in the 1970s than it is now. Fly-by-night businesses made a killing by offering to test if your marijuana had been sprayed with paraquat. A running joke among stoner comedians was that they would welcome if you’d send them your marijuana to sample for paraquat.

To circumvent the national outrage—which observers noted had been the first time that American students were really pissed off about something since the early 1970s—the government began rolling out plans to at least make paraquat pot detectable to the senses. There were suggestions about releasing a red dye along with the paraquat. Then there were plans to also use an extract of orange peel in the paraquat spray, which the State Department explained would give pot smokers ““the foulest‐smelling joint or brownie they ever had.”

It took a 1978 lawsuit from the National Organization to Reform Marijuana Laws to force the US Government to suspend funding for paraquat-spraying in Mexico until a comprehensive health study of its effects could be performed.

1980s: Reagan Administration Sprays Crops in Georgia

A scandal erupted in the state of Georgia in 1983 when it was uncovered that law enforcement officials had aided in smuggling drugs from south of the border into the USA. They had also facilitated the planting and cultivation of giant weed farms in Georgia’s Chattahoochee Forest.

In retaliation, the Reagan Administration ordered US helicopters to spray these weed plantations with paraquat and the DEA vowed to extend the practice to wherever weed was being grown in the USA.

For many, purposely damaging the lungs of pot smokers—perhaps fatally—was a punishment that far exceeded the crime. One critic likened the practice to placing land mines in NO PARKING zones.

Luckily, the practiced was quickly banned due to lawsuits filed based on environmental concerns.

Then in 1988, the DEA announced that it would resume spraying marijuana fields with the deadly substance.

The feds terminated this practice in the 1990s but paraquat remains one of the most commonly used herbicides on the market.

These days it is generally agreed that marijuana use is generally safe. In hindsight, the paraquat scare of the 1970s and 1980s seems like a case of “Reefer Madness” gone wild. It is unknown how many Americans were disabled or even killed by this sick and hysterical government policy. It is bitterly ironic that the same government which had for decades tried to insist that marijuana was bad for you had finally found a way to make it bad for you.