Anthrax AttacksAnthrax Attacks: 20 Years On

Twenty years ago this month the United States experienced the scary anthrax letter attacks, which targeted major media outlets and members of Congress. The anthrax spores were sent in letters, killing five people and sickened several more.

Scientists note that Bacillus anthracis, which causes anthrax, and its spores can “remain inactive for decades until they find a favorable environment to germinate, such as blood or tissue.” Infection can occur via inhalation, ingestion, and skin contact. Anthrax can be treated by certain antibiotics; however, inhalational anthrax is usually lethal if not diagnosed and treated very early.

IEEE Spectrum reports that iIn 2001, before the attacks, the Armed Forces Radiobiology Research Institute (AFRRI) was studying “how to render anthrax spores harmless through irradiation.” AFRRI’s work confirmed that electron beams and X-rays, both forms of ionizing radiation, could sanitize mail. An electron beam “passes through an electromagnetic lens, which focuses the beam on the target,” but due to limited penetration, e-beams could only be used on letters and flat envelopes. X-rays penetrate deeper, making them a better option for parcels and boxes.

Since the Postal Service needed to process about 1.8 million pieces of contaminated mail, e-beam and X-ray machines needed to be scaled up. Scaling up became a logistical nightmare as the processing facility could only push through about 2,000 kilograms per hour. Though it took weeks to process all the mail items and up to a few months to get the items to their intended destination, irradiation was the key to decontaminating nearly 2 million pieces of mail after Amerithrax.