From the L.A. Times:

Six years after California became the first state to adopt rules requiring regular shade, water and rest for outdoor workers, adherence remains sporadic at best. Enforcement of the rules governing the state's 35,000 farms and other outdoor operations is sketchy, and many workers don't fully understand the protections they are entitled to.

State officials had been debating instituting heat standards for 15 years before Gov. Arnold Schwarzenegger in 2005 enacted an emergency measure after half a dozen workers collapsed and died. Since 2006, California has confirmed nine deaths of agriculture and landscape workers due to heat-related illness. This year, workplace-safety officials have said they are investigating three possible heat-related deaths of agricultural workers.

According to the current standard, employers must make one quart of water per hour available to each worker and provide enough shade to cover one-quarter of the workforce when temperatures hit 85 degrees. Companies also must conduct training on heatstroke prevention and have an emergency plan in place for workers who become ill.

For more, see: California farmworker protections not going far enough?