The public needs more protection from farming pesticides, a report warns.
The commission said people should be given more information
The Royal Commission on Environmental Pollution report said more research was needed into a possible link between pesticides and ill health.
It recommended in the meantime no-spray zones to reduce potential risk to the public and more information on sprays.
Ministers will study the findings before responding. The Crop Protection Association said it was confident pesticides were safe if used correctly.
Former rural affairs minister Alun Michael called for the report in June 2004 to address growing controversy over whether human health was at risk from the use of agricultural pesticides.
It followed claims from a number of sick people that crop spraying had caused illnesses including nervous disorders, depression and even cancer.
Royal Commission (RCEP) chairman Sir Tom Blundell told BBC Breakfast: "We have a large number of people who live next to arable fields that are sprayed and a number of them, a few hundreds, are ill, and they think they are ill because they've either been sprayed or spray drift has come over their homes.
"The question is how do we link these illnesses to the cause, and is the cause spraying?
"It's very uncertain science, but we feel there is a plausibility that some of those ill [people] are ill because of spraying."
Government policy did not take into account the scientific uncertainty about the effects of the chemicals, the RCEP said.
The code of practice used by farmers should be strengthened so that people living next to fields received advance warning if the area was to be sprayed, it said.
Sir Tom said: "Most farmers are very responsible and most spraying is done by very professional people, but I think we need to have a little bit more statutory regulation so that we know, and everybody knows, that the rules are being followed."
The RCEP recommended five-metre no-spray strips between sprayed land and homes.
Peter Sanguinetti, chief executive of the Crop Protection Association, told BBC Radio 4's Today that two-metre buffer strips were coming in under the EU Common Agricultural Policy.
"This whole industry is very, very strictly regulated," he said.
"The regulation doesn't just cover the approval of a product, but how it is used - there are laws which lay down how it should be used by the farmers and operators, there are codes of practice.
"We go further than that as a responsible industry and promote a scheme called the voluntary initiative, which is best practice to make sure the machinery is accurate, and [spray] shouldn't drift into somebody's house... and that the sprayer is trained to the latest best practice."
He said: "We are confident that our products are safe when used correctly."
The RCEP study considered scientific evidence in areas including health, exposure and risk and found grounds for concern in all of them.