"Exemptions can be canceled if the Food and Drug Administration determines that a farm may be a source of contaminated produce," he said.

"And finally, keep in mind that growers of any size who sell at least some of their crop through wholesale marketing channels, even if technically not covered by the federal regulation, have been facing and will continue to face standards at least as stringent as anything in the final regulations."

LaBorde provided highlights of the requirements FDA would issue in the final regulation:

• Worker health and hygiene: Farm and packing-house workers who harvest or handle fresh produce, and their supervisors, must receive training on personal hygiene and health conditions that can increase the risk of food contamination. Growers are required to show proof of training by keeping written records.

Also, toilet facilities have to be readily accessible, kept reasonably clean and supplied with toilet paper. Hand-washing stations must be close to toilet facilities and supplied with potable running water, hand soap and clean, single-use towels.

• Agricultural water: Growers must be able to demonstrate that the water they use for irrigation, pesticide preparation, cooling and washing, and so forth is safe for its intended use. Maximum average E. coli levels of 126 cells per 100 milliliters have been proposed for irrigation water that can contact the edible part of the crop.

Water used for post-harvest operations faces more stringent standards. No detectable levels of E. coli are allowed.

• Biological soil amendments: At least a nine-month interval would be required between application of raw animal manure to produce fields and harvesting if there is a possibility that the manure may contact the produce. Composted animal manures can be applied from zero to 45 days before harvest depending on whether or not it can contact the crop.

Growers or their commercial compost suppliers must provide proof through laboratory testing that the composting process was adequate to make their compost safe to use. No human waste is allowed on fields except in the case of sewage sludge biosolids that are treated according to already existing regulations.

• Domesticated animals: Working animals, such as mules and horses, are allowed in produce fields as long as the grower can demonstrate that he or she has taken adequate measures to prevent contamination. If animals are allowed to graze in areas intended for produce growing, the nine-month waiting period specified for application of raw manure would apply.

• Wild animals: The Food and Drug Administration recognizes that it is impossible to keep all wild animals away from produce fields. If the situation is out of control and there is a reasonable probability that wild animals can contaminate produce, growers would be required to monitor their fields for signs of animals and take some kind of preventative measure to keep them out or discourage them from entering.

• Equipment, tools, and buildings: Equipment and tools need to be kept reasonably clean. Sanitation standards for packing buildings require good water drainage, control of dripping condensation, a pest-control program and regular clean-up of trash. Partially enclosed packing buildings are acceptable if the grower or packer takes precautions to prevent birds and other pests from becoming established in the buildings.

"Remember, this is a proposed rule and it is not a final regulation," LaBorde said. "This means that growers have an opportunity to comment on any part of the rule they do not understand or that they object to."

The draft ruling is available for viewing online at http://www.fda.gov/Food/FoodSafety/FSMA/ucm304045.htm. The public can submit comment on the draft rule until May 16. Before this date, the Food and Drug Administration will be holding public meetings to explain the proposal and to provide additional opportunity for input.

There are two ways to send comments. They may be submitted through the Internet at http://www.regulations.gov. Instructions for submitting comments are on the site.

Also, written comments may be faxed to FDA at 301-827-6870, or mailed to the Division of Dockets Management (HFA-305), Food and Drug Administration, 5630 Fishers Lane, Room. 1061, Rockville, Md., 20852. All written submissions received must include the Docket No. (FDA-2011-N-0921).