CHAFF, also known as “window” or Düppel, radio-frequency countermeasure used by modern militaries to obscure aerial movements from enemy radar systems. It is also used domestically during training and weapons testing. Chaff is made from thin strips of aluminum, metallized glass fiber, or plastic, which are dispersed into the air to produce scattered and disrupted radar projections. Chaff occasionally comes to public attention when it causes unintended disruptions, appearing as heavy rainfall on weather radars or interfering with air-traffic-control operations. The technology was invented during World War II, developed independently by researchers in the United Kingdom, Germany, Japan, and the United States. The first recorded use of chaff by American forces in combat was on December 20, 1943, in an air raid over Bremen, Germany, by 8th Air Force bombers.
By strategically cutting thin, reflective aluminum strips or wires to half of the target radar’s wavelength, researchers found that the resonance and
re-radiation produced made it nearly impossible for enemy radar systems to distinguish between aircraft and the radiation echoes caused by the chaff. And though chaff quickly loses speed after being projected, resulting in a measurable discrepancy in radar return between the chaff cloud and the aircraft, modern technologies have been devised to counter this filtering, such the JAFF or CHILL techniques, in which an additional jammer broadcaster on the aircraft reflects a defensive radar signal off the chaff to match the frequency of the aircraft, resulting in a noisy signal leading to the detection of multiple false targets. Given that at least five hundred tons of chaff is released into the air annually in the United States during military-training exercises, many have raised concerns about the potential toxicity to humans, livestock, and the environment. Though today chaff is made of lightweight aluminum-coated fiberglass “dipoles,” for decades leadbased chaff accounted for up to 7.5 percent of all chaff used. The Department of Defense has reportedly phased out the use of lead-based chaff, but it was still manufactured up until 1987, and it remains in the DOD’s inventory.
Few reports or studies have been published on the topic of chaff toxicity. Though a handful of DOD-sponsored research reviews found the environmental and health impacts of chaff to be “negligible,” such findings remain at odds with widely accepted scientific conclusions about the deleterious effects of the wide dispersal of foreign and toxic materials into the atmosphere. An evaluation of the extant research by the Government Accountability Office found that “9 out of 10 reports cited gaps in information on potential effects [and] six of the nine made no recommendations but cited missing data, suggested additional studies or long-term monitoring, and cited possible longterm chronic effects.” To date the Department of Defense has announced no plans to address the concerns raised in the report.