Four proposed rules intended to help prevent foodborne illness have been updated by the U.S. Food and Drug Administration (FDA).

The agency said on Friday that it had revised the proposed rules based on feedback received from the public. The rules will implement portions of the FDA Food Safety Modernization Act (FSMA), which aims to strengthen food safety by shifting the focus to preventing food safety problems rather than responding to problems that arise.

As a result of public comments, the FDA plans to revise the water quality testing provisions in the proposed produce safety rule to account for natural variations in water sources. It also intends to adjust its approach to manure and compost used in crop production pending further research on this issue.

Additionally, the agency is proposing a new definition of which farms would be subject to the produce-safety rule. It would exclude farms with $25,000 or less in produce sales, rather than setting the threshold based on sales of all foods produced on the farm. The revision also simplifies which entities are covered by the produce safety rule and which would be covered by the preventive controls rules.

On the issue of spent grains, produced as a by-product of alcoholic beverage brewing and distilling and commonly used as animal food, the FDA said that concerns were raised that the proposed rules would require brewers and distillers to comply with the full human food and animal food rules if they made their wet spent grains available for animal feed. However, the updated proposed rule is intended to clarify that human food processors that create by-products used as animal food and are already complying with FDA human food safety requirements would not need to comply with the full animal food rule.

Lastly, revisions to the proposed rule on foreign-supplier verification would give importers more flexibility to determine appropriate supplier verification measures based on risk and previous experience with their suppliers.

Michael R. Taylor, the FDA's deputy commissioner for foods and veterinary medicine, said that the updates to these four proposed rules would "ensure a more flexible and targeted means to ensure food safety."