Occupational heat-related illnesses reported in California have increased from 2000 to 2017. The highest illness rates are reported in the Southern California counties of Los Angeles, San Diego, and Imperial.

The link between heat exposure and heat-related illnesses in workers is well documented globally. Heat-related illnesses encompass a broad range of symptoms, including headaches, dizziness, cramps, rapid heartbeat, and disorientation to more serious outcomes, including heat stroke. Although largely preventable, heat-related illnesses often occur among employees with little control over their work environment and limited ability to take appropriate actions when working under hot conditions. For more information, download the Occupational Heat-related Illness chapter.

What does this indicator show?

Occupational heat-related illnesses

This graph presents annual rates of occupational heat-related illnesses (HRI) per 100,000 California workers from 2000 to 2017 based on an analysis of workers’ compensation claims.

Source: Workers’ Compensation Information System data,
California Department of Industrial Relations (Heinzerling et al., 2020)

• Heat-related illnesses among workers have increased from about 3.5 per 100,000 workers in 2000 to 10 per 100,000 workers in 2017. These numbers are based on reported cases in workers’ compensation claims. 
• Illness rates among workers in three Southern California counties were over three times higher than the statewide rate in 2017. Rates were highest in Imperial County, followed by San Diego and Los Angeles counties.

• Occupational heat-related illnesses have continued to increase in California. Tracking these illnesses can help assess the effectiveness of the current heat-related illness prevention standard and inform other actions and policies to protect workers.
• Workplace heat-related injuries in CA cost millions of dollars each year in health care expenditures, lost wages and productivity, and disability claims.

• Heat-related illnesses cases generally occur during periods of exceptionally warm temperatures. Cases spiked in 2006, the year California experienced a prolonged heat wave. A sharp uptick in cases also occurred in 2017 when summertime temperatures were exceptionally warm.
• Rates of occupational heat-related illnesses vary by industry and occupation, and demographics. Workers at greater risk of heat-related illnesses include:
  • People who perform heavy labor or work outdoors
  • Police and firefighters
  • Farmworkers, particularly those who work long days during the summer and have limited control over their work schedule and job tasks.
  • People with underlying vulnerabilities, such as those who are lower income, have chronic illnesses, or have no health insurance; these workers are often from communities of color.

Workers pick cantaloupe melons at Del Bosque Farms in Firebaugh, California, on June 12, 2017. Temperatures reached 100 degrees on this day.

Credit: Joe Proudman/UC Davis

• California Department of Industrial Relations (DIR), CalOSHA Heat illness prevention
• California Department of Public Health (CDPH), Occupational Health Watch
• Centers for Disease Control and Prevention (CDC), OSHA-NIOSH Infosheet: Protecting Workers from Heat Illness