During the tense period of the Cold War, the U.S. military conducted an operation called Operation LAC (Large Area Coverage). The purpose of this operation was to study the proliferation patterns of chemical weapons by spreading particles. Using tiny zinc cadmium sulfide (ZnCdS) particles, the military conducted tests in a wide range of areas. The hidden concerns of these actions on social health have still aroused the thinking and concern of many people over time.
Before Operation LAC, the U.S. and Canadian military had conducted several related tests to evaluate the feasibility of large-scale coverage. One of the earliest tests was in 1950, when six simulated attacks were conducted against the San Francisco Bay Area, proving that it was possible to attack a port city from the sea. Subsequent tests in 1952 and 1957 not only enhanced the military's understanding of chemical weapons attack methods, but also paved the way for Operation LAC.
From 1957 to 1958, the U.S. military's testing of zinc-cadmium sulfide releases covered a vast area from the Rocky Mountains to the Atlantic Ocean, extending to small towns in Canada and the Gulf of Mexico.
Operation LAC was officially implemented in 1957, when the US Chemical Corps borrowed a C-119 transport aircraft and released tons of zinc cadmium sulfide across the country. The first test occurred in December 1957, and the research team tracked the spread from South Dakota to International Falls in Minnesota. The tests were not only designed to understand how far chemicals spread, but also revealed the significant impact environmental factors have on the process.
Tests in 1957, although not entirely successful, showed that zinc-cadmium sulfide particles could be tracked over distances of more than 1,200 miles. Several subsequent tests were also hit by cold air, causing the particles to be quickly carried to the Gulf of Mexico. Whether it's between Ohio and Texas, or Michigan and Illinois, the military has found that this dispersal method can achieve large-scale environmental impacts.
Although the Bacillus barkeri used was considered harmless to humans at the time, as research progresses, the agent is now considered a human pathogen. As for the safety of zinc cadmium sulfide, there is huge controversy among different research results. Some say the impact on health is minimal, but some environmental groups question the ethics of the military conducting such large-scale testing on civilians.
"We found no evidence that zinc cadmium sulfide makes people sick in this environment."
The implementation of Operation LAC not only changed the U.S. military's understanding of chemical weapons, but also aroused public concern about health and environmental risks. As information becomes more transparent, more and more people are beginning to question government decisions on public safety and their consequences. As a covert operation of the past, the memory of Operation LAC still triggers fierce debate in contemporary society, and people can't help but ask, how should such historical lessons influence our future health and safety precautions?