Drug Residue in South Korea's Sewage Declines, But Meth Use Among Foreigners Surges

According to a report released by the Ministry of Food and Drug Safety (식품의약품안전처) on June 12, 2025, the amount of drug residue found in the country's sewage has decreased for four consecutive years. However, in areas with a high concentration of foreign workers, the estimated use of methamphetamine (필로폰) has reached 141% of the national average. The report indicates that the total estimated usage of major illegal drugs, including methamphetamine and cocaine, has dropped from 31.27 mg per 1,000 people in 2020 to 15.89 mg last year. This data was gathered from samples taken and analyzed at major sewage treatment plants across the nation.

Despite the overall decline, methamphetamine was detected in all 34 sewage treatment plants surveyed, suggesting a widespread distribution of drug offenders throughout the country. Considering that an average user consumes about 30 mg of methamphetamine, it is estimated that one in every 3,000 people used meth last year.

Regionally, Incheon and the Siheung area of Gyeonggi Province, which have a significant number of foreign workers, showed relatively high levels of methamphetamine use. In 12 sewage treatment plants located in areas with a foreign population exceeding 6% and more than 500 foreign workers, the estimated methamphetamine usage was approximately 141% of the national average.

The Ministry noted that this trend aligns with the increasing number of foreign drug offenders, which rose from 2,573 in 2022 to 3,232 last year, according to the Supreme Prosecutors' Office (대검찰청). In response, the government plans to implement a joint task force composed of the National Police Agency (경찰청) and the Supreme Prosecutors' Office to conduct focused crackdowns on facilities with high foreign populations to curb the spread of illegal drug use.

Some experts believe that the decrease in overall drug use may be attributed to a rise in the use of alternative drugs. In light of this, the Ministry plans to expand its analysis from 15 illegal drugs to over 200 substances, including medical and new psychoactive drugs. They aim to actively respond to trends in drug influx, usage changes, and take swift action on substances not yet classified as temporary drugs.

Additionally, in cities with high mobility, the Ministry intends to collect samples from more than ten drainage points and, if drug components are detected, conduct further sampling from related facilities to enhance traceability.

The Ministry also plans to conduct cohort studies targeting groups exposed to specific risk factors in collaboration with medical institutions frequented by drug addicts. They will analyze the correlation between hydrological data and socio-demographic and economic data using data science to estimate the distribution of drug use in various regions.

The Minister of Food and Drug Safety, Oh Yu-kyung (오유경), emphasized that the detection of illegal drugs in all sewage treatment plants for five consecutive years is a serious issue that cannot be ignored. She called for a united effort from the public to eradicate illegal drug use and assured that the government will continue to seek effective measures to address this problem.

Sewage sample analysis is a method used in countries like Australia and the European Union (EU) to identify the types of drugs being used. If drugs are found in the samples, it is likely that someone disposed of drugs in a restroom or that residual drugs were excreted by users.