CIA prewar reports on Iraq’s alleged weapons of mass destruction (WMD), were “all wrong,” according to the Presidential Commission on U.S. intelligence capabilities.

That is no surprise. In a June 2003 column “Intelligence without brains,” I showed how anyone capable of critical thought could easily see the October 2002 CIA report on “Iraq’s Weapons of Mass Destruction” was an amateurish collection of inconsistent speculations, rumors and hunches.

The report lacked not merely facts but common sense. The commission found the CIA’s worst errors were due “chiefly to flaws in analysis,” and to the “fundamental assumptions and premises of its analytic judgments,” and “an inferential leap.”

The panel blamed insufficient imagination. The greater danger may be too much imagination — dreaming up long-shot science-fiction scenarios, like those recently leaked from the Homeland Security Department involving demonstrably ineffective agents delivered by inexplicable devices.

In the partially prescient 1996 Kurt Russell film “Executive Decision,” Islamic terrorists hijack an airliner to kill “millions of Americans” with bombs filled with sarin nerve gas. Jet fuel would have been a less thrilling yet more realistic threat.

As the Economist noted two weeks after the September 11, 2001, terrorist attacks: “Although a few molecules of sarin are enough to kill a person, it takes hundreds of pounds of chemicals to achieve that concentration in an open air attack.”

On Oct. 2, 2001, the Washington Post’s reporters Joby Warrick and Joe Stephens found defense and intelligence agencies had become so enthralled with sarin, smallpox and other hypothetical “weapons of mass destruction” they didn’t connect three dots: commercial planes were often hijacked; jet fuel is explosive; suicidal terrorist tactics are common.

The article revealed “elaborate multiagency planning exercises with flashy names such as ‘Red Ex’ and ‘Dark Winter’ focused overwhelmingly on biological and chemical threats, while experts urging preparations for a simpler, more conventional attack found it difficult to be heard. … Lots of money poured into research on chemical and biological threats. Entire research institutes were created for it.”

The postwar death toll from bioterrorism is only six — five Americans from anthrax and one Bulgarian assassinated with ricin. The death toll from chemical terrorism is 26 — 19 from sarin gas in Japanese subways a decade ago and seven in Chicago in 1982 killed by Tylenol laced with cyanide.

In March 1999, The Post’s science writer Daniel Greenberg already sensed a “whiff of hysteria-fanning and budget opportunism in the scary scenarios of the saviors who have stepped forward against the menace of bioterrorism.”

Today, the federal cost of this bioterrorism bonanza is $7.9 billion a year — nearly $2 billion for each known victim of bioterrorism. Yet taxpayers are still assaulted by periodic hysteria-fanning studies from opportunistic institutes claiming, “The United States remains woefully unprepared to protect the public against terrorists wielding biological agents.”

Lumping nuclear weapons with a hodgepodge of biological and chemical agents as weapons of “mass” destruction is intended to imply germs and chemicals are as dangerous as nuclear bombs. In a January 2003 speech, former Deputy Defense Secretary Paul Wolfowitz claimed Iraq had enough ricin to kill “more than 1 million people,” botulinum toxin (botox) “to kill tens of millions” and anthrax “to kill hundreds of millions.”

To use ricin to kill many people, someone would have to dump hundreds of tons of it on a small area. To kill many with anthrax or botox, someone would have to first get the victims to sniff weapons-grade anthrax or eat botulism-contaminated food and then shun antibiotics or antitoxins.

Four months before the September 11 attacks, the Center for Strategic and International Studies hosted a “Dark Winter” war game that assumed the smallpox virus could somehow be released in three shopping malls without anyone noticing, leaving 3,000 unknowingly infected. Each victim was (wrongly) assumed to infect 10 more, through casual contact with travelers who didn’t notice their pox. Compounding supposedly resulted in a million deaths within two months. Dark Winter was cited as a reason the Bush administration spent a half-billion dollars on 300 million doses of smallpox vaccine and tried to force risky vaccinations on first responders.

Wall Street Journal science columnist Sharon Belgey debunked “Dark Winter” in November 2002, quoting Swiss expert Peter Merkle about “the sensationalistic press and marketing hype emerging from the burgeoning biodefense industry.” “Dark Winter” assumed everyone infected spread the infection to 10 others, but teams of researchers say the scenario is tenfold too large. “Smallpox spreads slowly and is not very contagious,” Miss Begley noted. Smallpox symptoms are quite visible, which acts like a big quarantine sign. Even a partial quarantine and local vaccinations have proven effective against smallpox.

After the Iraq invasion turned up no WMD, a Wall Street Journal editorial seized on inspector David Kay’s mention of Iraqi research on aflatoxin — a carcinogenic mold that is researched because excessive aflatoxin on nuts can result in export bans. A U.S. lab worker once tried to commit suicide by ingesting a lot of aflatoxin, but failed.

To use aflatoxin, anthrax, botox or ricin to kill more than a half-dozen people, you have to imagine some device for effectively delivering such agents. When it came to imaginary delivery systems, WMD fear-mongering escalated to the absurd.

The 2002 British dossier claimed, “Iraq can deliver chemical and biological agents using an extensive range of artillery shells, free-fall bombs, sprayers and ballistic missiles.” But biological agents (except ricin) are living organisms, which would be killed by any bomb, shell or missile. Chemical agents are liquid at room temperature, not gaseous, and most effective in closed spaces like a subway car or building.

Chemical agents can be delivered by artillery shells, but how could terrorists sneak into a city with a 4‑ton Howitzer? If terrorists can attack us with artillery shells, free-fall bombs or missiles, we should worry far more about conventional explosives than sarin shellings or aflatoxin bombs.

Former Secretary of State Powell told the United Nations that Iraq had “ways to disperse lethal biological agents widely, indiscriminately into the water supply, into the air.” But few biological agents (except anthrax) can survive sunlight, and none can survive chlorine. And it would take many huge trucks to poison a small water reservoir.

What about fears of biological agents dispersed indiscriminately into the air? Scenario spinners speculate about mixing anthrax with water and somehow spraying it (without detection) from trucks, crop dusters or unmanned aircraft. But to die from anthrax, you need to inhale thousands of spores. Those spores clump together and mix with dust, yet they must end up neither too large nor too small, or else they would be sneezed out, coughed up or swallowed. Even if enough particles of the perfect size could be sprayed into the breezes, the odds are extremely low of infecting more than few dozen people that way. And none would die if they took Cipro promptly.

The biggest danger of past and present alarmist statements about biological terrorism is that endless exaggeration of low-probability events continues diverting limited attention and resources away from real weapons real terrorists really use — airplanes, machine guns, arson, suicide bombs and car bombs.