Most US banknotes in wallets, cash registers, and bank vaults carry microscopic traces of cocaine, not because most bills were rolled up for drug use, but because paper money acts like a fibrous trap as it passes through high-speed counting machines and thousands of hands. Forensic studies detect trace cocaine on 67% to 92% of circulated US banknotes (1 in 1.49 to 1 in 1.09), averaging 2.34 nanograms per bill across 4,174 notes.
Those quantities are measured in nanograms (billionths of a gram) or low micrograms (millionths of a gram), far below the threshold needed to produce any physiological effect, cause a positive workplace drug test, or alert a trained narcotics detector dog.
What forensic laboratory studies find on US bills
Analytical chemists have tested circulated US paper money for cocaine since the 1990s using capillary gas chromatography (capillary GC), gas chromatography coupled with mass spectrometry (GC-MS), and liquid chromatography coupled with mass spectrometry (LC-MS). Because modern laboratory instruments can detect cocaine down to single nanograms, the share of bills that test “positive” depends heavily on the detection cutoff used in a given study.
The largest multi-year examination of US paper currency was published in the Journal of Forensic Sciences in 2013 by Thomas H. Jourdan and colleagues at the FBI Laboratory and the University of Central Oklahoma. The researchers analyzed 418 currency samples totaling 4,174 bills across all six primary circulation denominations ($1, $5, $10, $20, $50, and $100) collected from 90 US locations over a 17-year period from 1993 to 2009. Across all 4,174 notes, the average contamination level was 2.34 nanograms of cocaine per bill, and the statistical probability that a randomly selected bill carried less than 20 nanograms of cocaine was 0.8349, or 83.49% (about 1 in 1.20, our arithmetic), leaving a 16.51% chance (about 1 in 6.06) of 20 nanograms or more.
| Study and publication year | Sample size and US scope | Share of bills positive (and odds) | Reported cocaine mass per bill |
|---|---|---|---|
| Jourdan et al., Journal of Forensic Sciences (2013) | 4,174 bills in 418 samples across $1, $5, $10, $20, $50, and $100 notes from 90 US locations (1993 to 2009) | 83.49% (1 in 1.20) carried under 20 ng; 16.51% (1 in 6.06) carried 20 ng or more | Mean of 2.34 nanograms (0.00234 micrograms) per bill |
| Zuo et al., Journal of Separation Science (2008) | Circulated US banknotes ($1 to $100) collected in southeastern Massachusetts (capillary GC) | 67% positive (1 in 1.49, our arithmetic) | About 2 nanograms to 49.4 micrograms per note |
| Jenkins, Forensic Science International (2001) | 10 randomly collected US $1 bills from each of 5 US cities (50 bills total, our arithmetic) | 92% positive, 46 of 50 bills (1 in 1.09, our arithmetic) | 0.01 to 922.72 micrograms (mean 28.75 micrograms; median 1.37 micrograms) |
| Oyler et al., Journal of Analytical Toxicology (1996) | 10 single dollar bills from each of several US cities | 79% above 0.1 micrograms (1 in 1.27, our arithmetic); 54% above 1.0 microgram (1 in 1.85, our arithmetic) | Up to 1,327 micrograms on a single bill |
Smaller regional and multi-city studies show how a few heavily contaminated notes skew the mean upward while the median bill holds only trace residue. In a 2008 study in the Journal of Separation Science, Yuegang Zuo and colleagues at the University of Massachusetts Dartmouth tested circulated banknotes collected in southeastern Massachusetts using a nondestructive capillary gas chromatographic (capillary GC) method and detected cocaine on 67% of the bills (1 in 1.49, our arithmetic) in quantities ranging from roughly 2 nanograms to 49.4 micrograms per note. Notably, mid-denomination bills ($5, $10, $20, and $50) carried higher average cocaine amounts than $1 and $100 bills.
In a 2001 Forensic Science International study, Amanda J. Jenkins of the Cuyahoga County Coroner’s Office in Cleveland analyzed 10 randomly collected $1 bills from each of five US cities (50 bills total, our arithmetic) by GC-MS without cutting or destroying the notes. Cocaine was present on 92% of the bills (46 of 50, or 1 in 1.09, our arithmetic), spanning a range from 0.01 to 922.72 micrograms per bill. Because one or two heavily exposed bills pulled the arithmetic average up to 28.75 micrograms (with a standard deviation of 139.07 micrograms), the median across the positive bills was much lower at 1.37 micrograms per bill. Similarly, a 1996 National Institute on Drug Abuse study by Jonathan Oyler, William D. Darwin, and Edward J. Cone in the Journal of Analytical Toxicology examined 10 single dollar bills from each of several US cities by GC-MS and found that 79% of the currency samples (1 in 1.27, our arithmetic) held more than 0.1 micrograms of cocaine and 54% (1 in 1.85, our arithmetic) held more than 1.0 microgram, with a single outlier bill reaching 1,327 micrograms.
Other substances detected on circulated $1 bills
Cocaine is far more prevalent on circulated cash than other illicit drugs, both because crystalline cocaine hydrochloride adheres readily to the linen-cotton fibers of US currency paper and because it is chemically stable in ambient air. When Jenkins tested the same 50 circulated $1 bills from five US cities for other controlled substances in 2001, detection rates dropped sharply below cocaine’s 92% mark.
| Substance tested on circulated US $1 bills | Sample size and study | Bills positive | Share positive (and odds) | Reported range on positive bills |
|---|---|---|---|---|
| Cocaine | 50 US $1 bills (our arithmetic) from 5 cities (Jenkins, 2001) | 46 (our arithmetic) | 92% (1 in 1.09, our arithmetic) | 0.01 to 922.72 micrograms/bill |
| Heroin | 50 US $1 bills (our arithmetic) from 5 cities (Jenkins, 2001) | 7 | 14% (1 in 7.14, our arithmetic) | 0.03 to 168.50 micrograms/bill |
| 6-Acetylmorphine (heroin metabolite) | 50 US $1 bills (our arithmetic) from 5 cities (Jenkins, 2001) | 3 | 6% (1 in 16.67, our arithmetic) | Range not reported in abstract |
| Morphine | 50 US $1 bills (our arithmetic) from 5 cities (Jenkins, 2001) | 3 | 6% (1 in 16.67, our arithmetic) | Range not reported in abstract |
| Methamphetamine | 50 US $1 bills (our arithmetic) from 5 cities (Jenkins, 2001) | 3 | 6% (1 in 16.67, our arithmetic) | Range not reported in abstract |
| Phencyclidine (PCP) | 50 US $1 bills (our arithmetic) from 5 cities (Jenkins, 2001) | 2 | 4% (1 in 25, our arithmetic) | 0.78 and 1.87 micrograms/bill |
| Amphetamine | 50 US $1 bills (our arithmetic) from 5 cities (Jenkins, 2001) | 1 | 2% (1 in 50, our arithmetic) | Range not reported in abstract |
| Codeine | 50 US $1 bills (our arithmetic) from 5 cities (Jenkins, 2001) | 0 | 0% (our arithmetic) | None detected |
| Cannabinol (CBN, cannabis degradation product) | 125 US $1 bills from 12 cities (Lavins et al., 2004) | 13 | 10.31% (1 in 9.70, our arithmetic) | 0.014 to 0.774 micrograms/bill (14 to 774 nanograms/bill; mean 166 nanograms/bill, our arithmetic) |
| Delta-9-THC (active cannabis compound) | 125 US $1 bills from 12 cities (Lavins et al., 2004) | 2 | 1.6% (1 in 62.5, our arithmetic) | 0.085 and 0.146 micrograms/bill (85 and 146 nanograms/bill, our arithmetic) |
| Cannabidiol (CBD) | 125 US $1 bills from 12 cities (Lavins et al., 2004) | 2 | 1.6% (1 in 62.5, our arithmetic) | 0.032 and 0.086 micrograms/bill (32 and 86 nanograms/bill, our arithmetic) |
In Jenkins’s 2001 sample of 50 bills (10 bills from each of five cities, our arithmetic), heroin was the second most common substance at 14% (7 of 50 bills, or 1 in 7.14, our arithmetic) in amounts ranging from 0.03 to 168.50 micrograms per bill, followed by 6-acetylmorphine, morphine, and methamphetamine at 6% each (3 of 50 bills, or 1 in 16.67, our arithmetic; microgram ranges not reported in the abstract), phencyclidine (PCP) at 4% (2 of 50 bills, or 1 in 25, our arithmetic, at 0.78 and 1.87 micrograms per bill), amphetamine at 2% (1 of 50 bills, or 1 in 50, our arithmetic; amount not reported in the abstract), and codeine at 0% (0 of 50 bills, our arithmetic). A follow-up 2004 study in the Journal of Analytical Toxicology by Eric S. Lavins, Bethany D. Lavins, and Amanda J. Jenkins analyzed 165 randomly collected banknotes from 12 US cities (125 US $1 bills) and four foreign countries (40 notes) by GC-MS with selected ion monitoring: on the US $1 bills, cannabinol (CBN) appeared on 10.31% (13 notes, or 1 in 9.70, our arithmetic) at 0.014 to 0.774 micrograms per bill (14 to 774 nanograms per bill, with a mean of 0.166 micrograms or 166 nanograms per bill, our arithmetic), while delta-9-tetrahydrocannabinol (THC) appeared on 1.6% (2 notes, or 1 in 62.5, our arithmetic, at 0.085 and 0.146 micrograms or 85 and 146 nanograms per bill) and cannabidiol (CBD) appeared on 1.6% (2 notes, or 1 in 62.5, our arithmetic, at 0.032 and 0.086 micrograms or 32 and 86 nanograms per bill).
How mechanical bill counters spread residue across 56.6 billion notes
Why do up to 9 out of 10 bills carry trace cocaine when only a small fraction of the population uses the drug? According to the Substance Abuse and Mental Health Services Administration (SAMHSA) 2024 National Survey on Drug Use and Health, 14.7% of US residents aged 12 or older (42,408,000 people, or 1 in 6.80, our arithmetic) have used cocaine at least once in their lifetime, 1.5% (4,257,000 people, or 1 in 66.67) have used it in the past year, and 0.6% (1,671,000 people, or 1 in 166.67) have used it in the past month.
Only a small share of banknotes ever touch cocaine directly during illicit transactions or intranasal use, when a single bill can pick up hundreds of micrograms of powder. Once those heavily contaminated bills enter retail registers, automated teller machines, and bank sorting equipment, high-speed friction rollers rub microscopic crystals from one note onto the linen-cotton surface of neighboring notes. According to the Federal Reserve Board, 56.6 billion US banknotes were in circulation as of December 31, 2025, led by 19.9 billion $100 notes (35.2% of all notes, our arithmetic), 15.2 billion $1 notes (26.9%), and 11.0 billion $20 notes (19.4%), alongside 3.7 billion $5 notes (6.5%), 2.5 billion $50 notes (4.4%), 2.4 billion $10 notes (4.2%), and 1.8 billion $2 notes (3.2%). Because $1, $5, $10, and $20 notes change hands and pass through commercial counting machines constantly, low-nanogram background contamination quickly equalizes across general circulation.
That distinction between nanogram background transfer and recent heavy contact is critical in forensic chemistry and court proceedings. In the 1996 Oyler et al. study, the authors noted that contamination was likely primarily a result of cross-contamination from other bills and money-counting machines, and Jourdan et al. (2013) established the 2.34-nanogram average across 4,174 bills specifically to give courts a baseline for normal background contamination. Likewise, a 2002 study by Kenneth G. Furton and colleagues at Florida International University in the Journal of Chromatographic Science showed through field tests with trained drug detector dogs that methyl benzoate is the dominant signature odor chemical along with cocaine on US currency, requiring a threshold of roughly 1 to 10 micrograms when spiked (or 10 nanograms per second diffused from polymer bottles) to initiate an alert, and concluded that the microgram levels of cocaine reported on circulated US currency are insufficient to signal an alert from law-enforcement trained detector dogs.
The short version
Peer-reviewed laboratory studies detect trace cocaine on 67% to 92% of circulated US banknotes (1 in 1.49 to 1 in 1.09), with the largest multi-year forensic dataset of 4,174 bills across 90 US locations averaging 2.34 nanograms per bill and showing an 83.49% probability (1 in 1.20) that a random bill carries less than 20 nanograms. While 1.5% of Americans aged 12 or older (1 in 66.67) report using cocaine in the past year, mechanical bank counters transfer microscopic crystals from a small number of heavily exposed bills across the 56.6 billion US banknotes in circulation, leaving trace amounts that cannot cause intoxication, a positive drug test, or a detector dog alert.
If you or someone you know is struggling with substance use, free and confidential support is available 24/7 from the SAMHSA National Helpline at 1-800-662-4357.
Last checked: October 27, 2026, against peer-reviewed forensic chemistry studies indexed in PubMed (1996 to 2013), Federal Reserve Board currency circulation volume data through December 31, 2025, and the 2024 SAMHSA National Survey on Drug Use and Health. This article was machine-checked against the sources above and has not been expert-reviewed. Spotted an error or a newer public figure? Please tell us on our contact page with the article link and we will review it.
Sources
- S1 Jourdan TH, Veitenheimer AM, Murray CK, Wagner JR. The quantitation of cocaine on U.S. currency: survey and significance of the levels of contamination. Journal of Forensic Sciences. 2013;58(3):616 to 624. PMID 23550619. https://pubmed.ncbi.nlm.nih.gov/23550619/ Accessed Oct 27, 2026.
- S2 Zuo Y, Zhang K, Wu J, Rego C, Fritz J. An accurate and nondestructive GC method for determination of cocaine on US paper currency. Journal of Separation Science. 2008;31(13):2444 to 2450. PMID 18646272. https://pubmed.ncbi.nlm.nih.gov/18646272/ Accessed Oct 27, 2026.
- S3 Jenkins AJ. Drug contamination of US paper currency. Forensic Science International. 2001;121(3):189 to 193. PMID 11566423. https://pubmed.ncbi.nlm.nih.gov/11566423/ Accessed Oct 27, 2026.
- S4 Oyler J, Darwin WD, Cone EJ. Cocaine contamination of United States paper currency. Journal of Analytical Toxicology. 1996;20(4):213 to 216. PMID 8835657. https://pubmed.ncbi.nlm.nih.gov/8835657/ Accessed Oct 27, 2026.
- S5 Lavins ES, Lavins BD, Jenkins AJ. Cannabis (marijuana) contamination of United States and foreign paper currency. Journal of Analytical Toxicology. 2004;28(6):439 to 442. PMID 15516293. https://pubmed.ncbi.nlm.nih.gov/15516293/ Accessed Oct 27, 2026.
- S6 Furton KG, Hong YC, Hsu YL, Luo T, Rose S, Walton J. Identification of odor signature chemicals in cocaine using solid-phase microextraction-gas chromatography and detector-dog response to isolated compounds spiked on U.S. paper currency. Journal of Chromatographic Science. 2002;40(3):147 to 155. PMID 11954652. https://pubmed.ncbi.nlm.nih.gov/11954652/ Accessed Oct 27, 2026.
- S7 Board of Governors of the Federal Reserve System. Currency in Circulation: Volume (Updated March 6, 2026). https://www.federalreserve.gov/paymentsystems/coin_currcircvolume.htm Accessed Oct 27, 2026.
- S8 Substance Abuse and Mental Health Services Administration. 2024 National Survey on Drug Use and Health (NSDUH) Detailed Tables (Section 1 PE Tables 1.1A and 1.1B) and SAMHSA National Helpline. https://www.samhsa.gov/data/data-we-collect/nsduh-national-survey-drug-use-and-health/national-releases/2024-nsduh-detailed-tables and https://www.samhsa.gov/find-help/helplines/national-helpline Accessed Oct 27, 2026.