That dizzy feeling isn't the weed - Chinese pesticides used on pot farms linked to nausea, memory loss and even cancer

Cannabis users who get headaches from their pot may need to look more carefully at their supply.

New research shows how some of the most popular brands on California’s dispensary shelves contain alarmingly high levels of pesticides.

They can irritate the lungs, eyes, and throat and cause rashes, headaches, diarrhea and abdominal pain.

Worse still, contaminants can include chemicals linked to cancer, liver failure, thyroid disease and genetic and neurologic harm to users and unborn children.

Some chemicals have been smuggled in from China — a sign of the growing involvement of Chinese gangs in legal and contraband pot farming in the US in the wake of legalization.

An LA Times and WeedWeek investigation probed some of the most popular brands of vapes and pre-rolled weed in the Golden State.

Some 25 of 42 legal pot products bought from stores and tested at private labs showed concentrations of pesticides above state or federal safety levels.

Most of the pesticides found were in low concentrations that could harm people who used them regularly.

The full extent of the health threat may not be known for years, researchers warned.

Vapes were among the worst offender.

Researchers found that five well-known brands had pesticide loads above federal risk thresholds for harm from a single exposure

Some products contained as many as two dozen pesticides.

The alarming findings echo the results of other surveys these past eight months.

Cannabis farmers are understood to overuse pesticides to boost profits in a tight market.

The high-value crop needs protection from the insect infestations that thrive in greenhouses.

Meanwhile, the surging popularity of vaping has driven demand for vape oils that are made from lower-quality weed, often grown illegally.

The potency of pesticides on some farms is so strong now that state investigators are urged to wear respirators and take blood poisoning tests when they come across them.

Researchers highlighted bags of illegal Chinese-label fumigants found at a cannabis greenhouse in Siskiyou County, in northern California.

Tests revealed 10 pesticides in the unbranded product, two that can kill if inhaled.

The haul included isoprocarb, a Chinese fumigant that’s not approved for use in the US.

The study focussed on California, but raises concerns for weed users across the country who could be inhaling similar chemicals.

Marijuana is fully legal - for adult recreational and medicinal use - in 29 states. It is fully illegal in four states.

Laws in the remaining states are mixed, meaning the drug may be permitted for medicinal use, allowed only in the form of CBD oil, be decriminalized or be a combination of these.

According to Pew Research, half of US adults say they have used pot, and nearly a quarter say they’ve used it in the past year.

There has been a notable uptick in recent years in the number of grows linked to Chinese nationals.

Some of these have popped up recently in such states as Maine and Oklahoma, with their looser rules and lax enforcement.

Fifty members of Congress in February wrote to the Department of Justice asking for more information about illegal marijuana cultivation linked to Chinese nationals.

The pesticides report is not the first scare for cannabis users.

Dozens of weed products, including buds and rollups, were recalled last month due to the discovery of a toxic mold that is linked to lung infections.

California's Department of Cannabis Control (DCC) reported that the products might be filled with aspergillus - a fungus that grows on plants when they aren't stored or dried properly.

Inhaling aspergillus can cause a wide range of health issues including coughing up blood, asthma attacks, headaches, weight loss and in extreme cases, death.

There were 13 overall products that were subject to mandatory recalls including Northern Emerald's Tyson Undisputed Cannabis Flower, a brand promoted by professional boxer Mike Tyson.