Leaders of Conservative Judaism are seeking to protect workers and the environment at kosher food plants such as the one raided by federal agents this spring in Iowa. They issued draft guidelines Thursday for a kosher certification program meant as a supplement to the traditional certification process that measures compliance with kashrut. The proposed "hekhsher tzedek," or "certificate of righteousness," would be awarded to companies that pay fair wages, ensure workplace safety, follow government environmental regulations and treat animals humanely, among other proposed criteria. Support for the idea has been fueled by controversies at Agriprocessors Inc. in Postville, Iowa, the largest kosher meatpacking plant in the US. The company has been accused in recent years of mistreating animals and employees. In May, federal immigration officials raided the plant, arresting nearly 400 workers in one of the largest raids in US history. Agriprocessors has denied any wrongdoing. Most of those arrested were Guatemalan and Mexican nationals who were accused of using false identification or incorrect Social Security numbers. Leaders of Conservative Judaism must persuade kosher producers and certifiers to join the effort. The Orthodox movement oversees most of the kosher industry. Many of its leaders have criticized the Conservative Jewish proposal as unreasonable and unenforceable.