The fumes of aluminium phosphide can kill silently and invisibly. There is no antidote. Accordingly the product - used to kill rodents and insects in granaries - is banned from household use in the UAE, as in many countries.
And yet, as The National reports today, the stuff is still widely available for sale here - despite a sustained chorus of warnings and a series of tragedies.
Now there has been a new case. More tests will confirm or disprove the theory that aluminium phosphide has killed again, this time in Sharjah.
On Sunday, Habiba Hisham, 2, died and her brother Adbul Rahman, 6, fighting for his life. This newspaper reported yesterday that doctors first suspected food poisoning, and it's easy to see why: vomiting is a principal symptom of both food and pesticide poisoning.
But when officials investigated, they found that the deadly chemical had been used in an adjacent apartment, whose residents were out of town, leaving their front door sealed with tape.
What can match the horror, for parents, of such an unseen, unsuspected menace? Children tucked into bed in the evening are by morning nauseated and close to death - if they awaken at all. If the pesticide is found to have killed Habiba, the horror will be all the greater because while parents are powerless against such a menace, authorities are not.
In Ajman in 2010, Suhail and Ali Bakari, two of three five-month-old triplets died when a neighbour's home was fumigated. Experts warned of an "urgent need" for tighter regulation of retail sales of pesticides.
In May this year, 10 men who shared a flat in Dubai survived in a similar case, although all needed hospital treatment. (Experts say children, with their higher respiratory rates, are at more risk than adults.) That time, too, there were calls for a crackdown.
Officials are trying. This June, after learning of more non-fatal pesticide poisonings and after reviewing a long list of unexplained deaths in which pesticides may have been responsible, Dubai officials warned the public against using any of the 400-plus banned chemical pesticides.
It's not enough. Warnings are appropriate, but far more public education, an energetic hunt for illicit suppliers, and well-publicised prosecutions will all be needed if we are to be safe from the silent killer next door.