Army acknowledges Cold War-era tests that sprayed cadmium-containing fog over U.S. neighborhoods

The U.S. Army has acknowledged that it conducted secret tests in the 1950s and 1960s that sprayed a chemical fog over dozens of neighborhoods in the United States and Canada, a program now linked by some residents to cancer and other long-term health problems.

The tests, carried out during the Cold War to study how airborne agents might disperse through cities, used zinc cadmium sulfide (ZnCdS), a powder that residents say produced a thick, foul-smelling fog that clung to skin and made children ill. The Army says the experiments were intended to model the spread of biological weapons and selected areas such as St. Louis, Missouri, because officials believed their urban layouts resembled Soviet cities.

People who lived in targeted neighborhoods, including residents of the Pruitt-Igoe housing complex in St. Louis, describe trucks and rooftop devices releasing the fog, which often left a visible residue. They allege a spike in cancers and chronic illnesses in the decades after the tests and say they were not informed that ZnCdS, a cadmium-containing compound, had been used.

Cadmium compounds have been associated with a range of adverse health effects. According to public health assessments, inhaling cadmium in sufficient amounts over long periods can increase risks of cancer and cause kidney and lung damage; however, the Army has repeatedly said that the concentrations used in the Cold War experiments were low and unlikely to produce serious health effects.

The testing program covered dozens of locations, including St. Louis, Fort Wayne, Indiana, and Corpus Christi, Texas, as well as other cities across the United States and Canada. Military planners mapped dispersal patterns from ground vehicles and rooftop emitters to estimate how particles would travel through urban environments.

Despite the Army's acknowledgment of the tests and its public statements about exposure levels, key records from a government report that examined the fog's health risks remain missing, according to individuals and documents reviewed by reporters. The absence of those documents has fueled skepticism among former residents and public health advocates who say the available records are incomplete and inadequate for assessing long-term harm.

Former residents and community advocates have sought release of remaining documents and independent health studies to determine whether the testing contributed to cancer clusters and other illnesses. Some have called for medical monitoring, compensation and formal apologies. The Army and other government agencies have not announced any new large-scale health screenings tied specifically to the ZnCdS tests.

Cold War-era testing of dispersal patterns by U.S. military and federal agencies has been the subject of public scrutiny for decades. Officials have offered varying accounts of scope, intent and safety over time, and declassified material has periodically revealed additional test sites and methods. Federal and state health authorities generally require a combination of exposure data, epidemiological studies and toxicological evidence to establish causal links between past environmental exposures and disease, a process advocates say is hindered here by missing records and the passage of time.

The disclosures have renewed calls from affected communities and some lawmakers for a comprehensive review of archival material, fuller transparency about what was released and where, and assessment of potential long-term health impacts. The Army continues to maintain that the levels of ZnCdS used in the tests were low, while residents and advocacy groups press for broader investigation and access to any remaining records that could clarify the extent of exposure and risk.