The pesticide fipronil at the heart of Europe's latest food safety scare is found in common household products used to rid the family dog of ticks, kill lawn pests, and in cockroach bait.
It is also a prolific killer of bloodsucking red mites that can devastate poultry farms, but Europe prohibits its use on food-producing animals.
Tests with lab rats have observed toxic effects on the nervous system, and the pesticide is deemed dangerous to bees -- crucial crop pollinators -- causing it to be banned for crop farming in many countries.
For humans, the World Health Organization lists fipronil as "moderately hazardous".
With traces found in eggs from Dutch and Belgium, consumers are concerned. We asked the experts:
- Might I have been poisoned? -
At the levels reported, there seems to be little or no risk even for people who have eaten tainted eggs.
"Withdrawing the eggs from the market... is more important (for) reassuring the public about the safety of their food rather than protecting their health," said Alan Boobis, a toxicology professor at Imperial College London.
Neuro-behavioural effects observed in lab tests occurred only with repeated exposure at high doses, "and the effects are reversible, generally speaking," he told AFP.
A scientific paper published in 2004, reported that seven people known to have drunk fipronil in Sri Lanka, where self-poisoning is common, failed in their suicide attempts. Two had taken doses of 100 millilitres each (3.4 fluid ounces).
The group's symptoms included vomiting, agitation and seizures, but all recovered fully, within days.
Those doses, said Boobis, were "thousands and thousands of times higher" than anything the tainted eggs may contain.
The European Union considers a concentration of 0.72 milligrammes of fipronil per kilogramme of egg as the maximum safe level, even though exceeding this is not necessarily dangerous.
Eggs are withdrawn from the market at an even lower cut-off -- 0.005 mg/kg.
Studies so far have also found no evidence that long-term, repeated exposure heighted cancer risk, said Boobis.
- Should I stop eating eggs? -
That may depend on how old you are, and who you ask.
The British Food Standards Agency says the number of tainted eggs represented about 0.0001 percent of eggs imported into the UK each year, and there was "no need" for concern.
"Our advice is that there is no need for people to change the way they consume or cook eggs or products containing eggs."
The German BfR food and chemical safety advisory body, however, warns that the highest contamination levels measured in eggs so far may exceed recommended levels for children.
Even so, it stressed that "a short-term exceedance does not automatically mean that consumption of the food in question involves a health risk."
In the Netherlands authorities have also warned that eggs from 59 farms contained levels of fipronil too high to be eaten by children.
France, which has received some of the contaminated eggs, insisted that trace amounts of fipronil do not necessarily pose a health risk, and ordered further tests.
Belgium, which has blocked production from 51 farms, said fipronil concentrations found so far were "far below" EU limits, and there was no need for a recall.
Most of the contaminated eggs have been traced and destroyed.
For Boobis, "it seems very unlikely" that anyone could eat enough egg of the contaminated to get sick from fipronil, "even somebody who's at the top end of egg consumption."
"There is no evidence that this will impact human health in any way," added Chris Elliot, a food safety expert at Queen's University Belfast.
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