Michael R. Taylor, the Food and Drug Administration’s deputy commissioner for foods and veterinary medicine, in a July 15 interview said he wanted produce growers to know the F.D.A. was committed to developing, with their input, a final rule on produce safety that “prevents illnesses but that is also practical and adaptable to a wide diversity of growing conditions and practices.”

The F.D.A. on Jan. 13 issued for public comment its proposed rule to establish standards for growing, harvesting, packing and holding produce on domestic and foreign farms. Mr. Taylor urged growers and other stakeholders to provide comments on the proposed rule before Sept. 16, when the comment period, which already was extended once, is brought to a close.

Mr. Taylor pointed out Congress in passing the F.D.A. Food Safety Modernization Act provided guidance on what farms and what produce should be covered by the proposed rule. The F.S.M.A. directed F.D.A. to exempt from the proposed rule farms with food sales of less than $500,000, if half or more of the value of those sales comes from sales directly to consumers in any location, or to restaurants or retail outlets that are within the same state and no more than 275 miles from the farm. Those exempted farms still would be required to let consumers know the name and address of the farm where the produce was grown. Mr. Taylor said about 76,000 farms would be eligible for the qualified exemption.

The proposed rule would not apply to certain produce that constitute the lowest risk in terms of contributing to foodborne illness, Mr. Taylor said.

“This includes produce that is rarely consumed raw, such as potatoes, and produce that will receive a commercial ‘kill step,’ such as tomatoes and green beans going to a canning operation,” he said. Mr. Taylor said about 40,000 additional farms would be exempt from the rule because they only grow produce that meet those criteria.

Additionally, the F.D.A. proposed not to cover farms with food sales of $25,000 or less, regardless of who their buyers are. This would apply to about 34,000 farms.

“Altogether, these limitations mean that, of about 190,000 U.S. produce farms, about 150,000, or 79%, are not covered by F.D.A.’s proposed rule, and about 50% of domestic produce acres are not covered,” Mr. Taylor said. “Importantly, even with these limitations, the proposed rule covers the great majority, about 90%, of the acres planted in crops that are potentially vulnerable to harmful contamination.”

Some growers of produce items that have not been associated with foodborne illness outbreaks have asked why their operations and crops should be regulated.

“In enacting F.S.M.A., Congress told us to take a preventive approach to ensuring food safety,” Mr. Taylor said. “For produce, Congress said specifically that our rules should require those steps that are ‘reasonably necessary to prevent the introduction of known or reasonably foreseeable’ hazards. Illness outbreaks are, of course, one way to identify hazards that need to be prevented, but many outbreaks are never detected, and many detected outbreaks are never linked to a specific food. Past outbreaks are also poor predictors of the future. In fact, almost every year we have an outbreak associated with a produce item with no past history of reported outbreaks.

“We also know from experience that the failure to observe basic practices like use of appropriately clean water, employee hygiene and careful use of raw manure has the potential to introduce contamination that can make people sick. We have limited the scope of our proposed rule to commodities for which we believe the potential for illness is real, and, in keeping with our mandate from Congress, we have proposed steps that we think are reasonably necessary to prevent the introduction of reasonably foreseeable hazards.”

The proposed rule concentrates on the five principal pathways of contamination: water, soil amendments (for example, raw manure and composted manure), animals, worker health and hygiene, and equipment and building sanitation.

“But as I said, we made sure that the requirements in each area make sense for food safety,” Mr. Taylor said. “So when it comes to water standards and testing, the proposed requirements would apply only to water that is intended or likely to contact the harvestable portion of the crop or food-contact surfaces. In the same way, the proposed waiting periods between application and harvest for certain types of soil amendments would apply only when the soil amendments are likely to contact the harvestable portion of the crop. Our proposed animal intrusion standards do not require fencing or other exclusion measures but only awareness of significant animal activity and removal of any visibly contaminated produce.”

Mr. Taylor also indicated the F.D.A. was interested in providing flexibility in the requirements where possible.

“So, for certain requirements for water and biological soil amendments, if you can come up with an alternative that is scientifically established to provide the same amount of protection as the F.D.A.’s proposed rule, you would be permitted to use your alternative practice,” he said.

Mr. Taylor said once the final rule is in place, farms of various sizes will be given different deadlines to come into compliance with the smallest farms provided the widest timeframes to come into compliance.

“I am very pleased to see that F.D.A. is working hard to address important producer questions during the development of this rule,” said Hank Giclas, senior vice-president, strategic planning, science and technology, at Western Growers, Irvine, Calif., an association of California and Arizona fresh produce growers. “Their efforts will ensure that the industry can provide informed feedback during the comment period and will help improve the rules as well as facilitate compliance once the rules are finalized.”