Controversial pesticides linked to declines in bee populations may potentially harm the developing brains of unborn babies, European safety experts have ruled.
They have called for recommended exposure limits for the nicotine-like chemicals to be lowered while more research is carried out.
Three neonicotinoid pesticides are already subject to a temporary ban throughout the European Union because of concerns about harm to bees.
The two-year moratorium takes effect from this month. While accepting the ban, the UK Government has said it rejects the science behind it.
One of the banned chemicals is one of two neonicotinoids now at the centre of a new warning relating to human health.
A statement from the European Food Safety Authority (EFSA) said the insecticide imidacloprid "may affect the developing human nervous system".
Similar concern was expressed about another neonicotinoid called acetamiprid, which is not one of the those affected by the ban.
The move follows research on rats showing that offspring exposed to imidacloprid suffered brain shrinkage, reduced activity of nerve signals controlling movement, and weight loss.
Another rat study found that acetamiprid exposure led to reduced weight, survival, and response to startling sounds.
A panel of experts from the EFSA concluded: "Some current guidance levels for acceptable exposure to acetamiprid and imidacloprid may not be protective enough to safeguard against developmental neurotoxicity and should be reduced."
For imidacloprid, it was proposed that the current limit for people working with the pesticide (acceptable operator exposure level, or AOEL) be reduced from 0.08 milligrams per kilogram of body weight per day to 0.06 milligrams.
The same limit reduction was recommended for the acute reference dose (ARfD) which is the amount of a substance that can safely be ingested by anyone over a short time, usually one day.
There was no recommendation to lower the current acceptable daily intake (ADI), the amount that can safely be ingested daily for a lifetime, for imidacloprid which was considered sufficiently protective.
For acetamiprid, the experts called for the current ADI and AOEL of 0.07 milligrams and the ARfD of 0.1 milligrams both to be lowered to 0.025 milligrams per day.