Tox Tuesday: Dirty money

May 17, 2016

In a recent study that analyzed the genetic material on $1 bills, scientists found several reasons why you shouldn't put your money where your mouth is. Most of those reasons center on the dangerous bacteria and drug residue that is present on a high majority of bills circulating around the world today.

"It was quite amazing to us," said Jane Carlton, director of genome sequencing at NYU's Center for Genomics and Systems Biology where the university-funded study was performed on dollar bills. "We actually found that microbes are growing on money."

In the study, researchers identified 3,000 types of bacteria in all—many times more than in previous studies that examined samples under a microscope. The researchers could identify so many more species because high-speed gene sequencing and computerized database analysis allowed them to recognize life forms by their DNA. Even so, they could identify only about 20% of the non-human DNA they found in the study because so many microorganisms haven't yet been cataloged in genetic data banks.

The researchers explained in an article that the most abundant species they found on the money they tested was the kind that causes acne. Other bacteria found was linked to food poisoning, including Escherichia coli and Bacillus cereus, and bacteria that causes gastric ulcers, pneumonia, and staph infections. Some bills also carried genes of the Acinetobacter species, responsible for antibiotic resistance, the scientists said.

"A body-temperature wallet is a petri dish," Philippe Etienne, managing director of a company that makes special bank-note paper for 23 countries said.

Various kinds of bacteria is not all that can be found on money, however. Other studies have found traces of cocaine and other drug residues on as much as 90% of the paper money circulating in U.S. cities. In some cities drug residue levels are even higher, with close to 100% of the money testing positive for drugs.

Another article explains that money can become contaminated with cocaine during drug deals or if a user snorts the drug with a bill. Not all bills contaminated are directly involved in drug use, however. They can also become contaminated inside currency-counting machines at banks that simply transfer the cocaine from one bank note to another.

"It is so widespread now there are no uncontaminated notes out there. If you have a note in circulation for a few weeks then almost certainly we can detect drugs," Gerry Risbridger, a senior analyst at a forensic testing service provider said in an article. He also added that the historic low cost of street drugs like cocaine have added to the presence of the residue on bills.

Most scientists agree, however, that the amount of drug residue and bacteria found on bills are not enough to cause health risks. In fact, some of the dollars studied had .006 micrograms of cocaine, which is several thousands of times smaller than a single grain of sand.

Central banks and state treasuries usually worry more about counterfeiting and durability than microbiology, another article explains. With nearly 150 billion new bank notes circulated every year around the world, governments spend nearly $10 billion annually to provide people with notes that are fit to hold.

A U.S. one-dollar bill, for example, is printed on a cotton-linen blend and lasts little more than 21 months. However, to make cash more durable, countries from Canada to the Kingdom of Bhutan are printing bank notes on sheets of flexible plastic polymer film, with implications for the microbiology of money.

In one study testing the public-health effect of new currency materials, researchers at Australia's University of Ballarat tested bills from supermarkets, coffee shops and cafeterias in 10 countries. While levels of bacteria and drugs varied widely from place to place, they usually found fewer on polymer bills than on cotton-based ones.

"The thing about a polymer note is that it is not absorbent," Mr. Etienne said in the article.

Other researchers tried growing bacteria on seven different currencies. They found that some germs survived longer on the plastic bank notes, according to tests published last year in Antimicrobial Resistance and Infection Control. However, a human touch compounds the problem, the article explains, as bacteria can feed on the waxy residue of skin and oils that builds up on bills in circulation.

All that being said, the best way to avoid any complications from handling today’s dirty money is proper handwashing, which scientists say is critical especially before preparing food or touching your face and mouth. Alcohol-based hand sanitizers can improve compliance with hand hygiene and reduce the transmission of pathogenic agents as well.

Although disinfection and hygiene intervention studies have yet to really produce reliable results in this matter, scientists still agree it’s your best bet until other methods can be developed.

For more information, click here and check out the infographic below.

Neogen offers ELISA test kits for forensic toxicology, including that for cocaine and any other street drugs that just may happen to find their way onto a dollar bill. 


Infographic source:


Category: Life Sciences, Toxicology, Public Health, Toxicology, Microbiology, Toxicology