'I am not afraid of anything except for God and poison gas," said an Iraqi officer who had fought in the Iran-Iraq war. "It's like a ghost. You have no defence against it." Though not a target of poison gas as a member of the army using it, he knew what it did to its victims.

Poison gas is a terrifying weapon. People are still dying in Iran from the effects of ingesting it a quarter of a century ago. It is one of the few weapons to be banned with partial success between its first use on a mass scale in the First World War and again by Saddam Hussein with even greater intensity against Iranians and Kurds in the 1980s.

It is right, therefore, that the alleged attack by the Syrian armed forces using chemical weapons against Saraqeb, a rebel-held town south-west of Aleppo on 29 April, should be carefully investigated. Doctors told the BBC's Ian Pannell that after an artillery bombardment they treated eight people with breathing problems, some of whom were vomiting and others who had constricted pupils.

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One woman named Maryam Khatib later died. Her son Mohammed said: "It was a horrible, suffocating smell. You couldn't breathe at all. You'd feel like you were dead. I couldn't see anything for three or four days." Videos taken by local people show a helicopter dropping an object which appears to leave a trail of white vapour.

My experience of trying to report allegations of the deployment or use of such weapons over the years makes me cautious. Local people, including local doctors, are often sincerely convinced that some exotic weapon has been used against them, but they may not have past experience of either conventional or chemical attack.

For instance, doctors in Fallujah west of Baghdad suspect that non-conventional weapons must have been used against the city when it was stormed by US forces in November 2004. This might explain why so many malformed babies have been born since. It is impossible not to sympathise or suppress a feeling of rage over the sufferings of these people.

But, in blaming non-conventional weapons, people may underestimate what conventional munitions can do. In two weeks' fighting in Fallujah in 2004, US marine artillery units fired an average of 379 high-explosive 155mm shells a day into this small city. In addition, American jets flying overhead dropped 318 bombs and, together with helicopters, fired 391 rockets and missiles.

At the time, the Iraqi government of Iyad Allawi made the unlikely claim that just 200 buildings in Fallujah had been destroyed or damaged. A recently published book, The Endgame: The Inside Story of the Struggle for Iraq from George W Bush to Barack Obama by Michael Gordon and Bernard Trainor, from which the above figures are taken, reveals that the US marines "estimated that out of about 50,000 residences in the city, their operations had destroyed between 7,000 and 10,000, as well as 60 mosques". Perhaps this vastly excessive use of firepower is sufficient explanation for the appalling birth defects.

Allegations about the use of poison gas in Syria are made under the shadow of the notoriously false claims about Saddam Hussein's possession of weapons of mass destruction made to justify the Iraq war. Not surprisingly, this has made the public everywhere in the world dubious about stories about the possession or use of WMD being used to hoodwink them into supporting another war.

Of course, it is much against the interests of the Syrian government to use chemical weapons because this might provoke foreign military intervention. The Syrian army has no need to use it as a terror weapon because artillery, aerial bombardment and death squads are quite enough to frighten people into taking flight. There are already 1.5 million refugees outside the country.

Journalists bear a large measure of responsibility for giving credence to the stories peddled by Iraqi defectors, intelligence services and government about Saddam's WMD. In that case, it should have been self-evident that Iraqi defectors with juicy stories, and the opposition parties that promoted them, wanted to tempt the US into military action against Saddam. When it comes to chemical weapons, the Syrian opposition has similar and wholly understandable motives.

As for the credibility of Western government claims about WMD, it is worth recalling that they tolerated Saddam using poison gas on a mass scale. And they did more than just turn a blind eye. Joost Hiltermann, in his book A Poisonous Affair: America, Iraq and the Gassing of Halabja, writes that Western powers "sent repeated signals to Iraq that the regime could continue, and even escalate, chemical weapons use – which it did, with the Halabja attack [when thousands of Kurdish civilians died] as climax".