Thousands of workers become ill each year from working in high temperatures, and some die. Heat-related health problems range from the pain and discomfort caused by heat rash and heat cramps to much more serious conditions including heat exhaustion and heat stroke.
Exposures are of such a magnitude and character that a significant number of workers risk developing serious long or short term health effects.
OSHA as well as other state agencies and safety and health professionals have found that workers who work in a hot environment are at risk of a heat-related illness, and at an increased risk of injury. (http://www.osha.gov/SLTC/heatstress/index.html) Risk is reduced somewhat by giving a worker time to acclimatize, or adjust to working in heat, during two to three weeks of work in similar conditions. Heat acclimatization is reduced considerably after as little as four days.
The level of risk depends on the following:
Exposures resulting in prolonged increases in deep body temperature are associated with other disorders such as temporary infertility (male and female), elevated heart rate, fatigue, and irritability. In the first trimester of pregnancy, sustained core temperature above 102F may endanger the fetus.
According to the Center for Disease Control, certain groups, such as those “who are 65 years of age or older, are overweight, have heart disease or high blood pressure, or take medications that may be affected by extreme heat,” may be at a greater risk. (http://www.cdc.gov/niosh/topics/heatstress/)
Identifying situations that could require workers to perform tasks in high-heat conditions should be an integral part of the site safety planning process.
To determine if workers are at risk of heat-related illnesses consider the following:
It is important to note that temperature measured with a normal dry bulb thermometer does not fully measure the risk of heat stress. The American Conference of Governmental Industrial Hygienists (ACGIH) recommends work-rest cycles based on a "wet bulb globe temperature" ("WBGT). The WBGT approach measures the combined effects of the air temperature, air speed, humidity, and radiant heat as a 2-hour time-weighted average. This assumes lightly clothed acclimatized workers. The level of work activity is also taken into consideration. For example an individual working in a high temperature, performing “heavy work” would be at risk of heat stress sooner than if performing “moderate work.” ACGIH defines the levels of risk as follows:
The National Oceanic and Atmospheric Administration (NOAA) uses the term “heat index,” which only considers temperature and humidity, and is generally the basis for community excessive heat warnings. It does not consider work load or radiant heat sources. (http://www.weather.gov/om/heat/index.shtml)
There is no Federal OSHA standard specifically for working in high temperatures; however, hazardous work activities or exposures that are not covered by a specific standard are covered by the general duty clause, which requires each employer to provide a safe and healthful workplace.
OSHA has a national “Campaign to Prevent Heat Illness in Outdoor Workers” with information and materials targeted for workers, contractors and the general public. The goal is to raise awareness and reduce the number of heat-related illnesses and deaths. (http://www.osha.gov/SLTC/heatillness/index.html)
Federal OSHA Standards are enforced by the U.S. Department of Labor in 26 states. There are currently 22 states and jurisdictions operating complete state plans (covering both the private sector and state and local government employees), and 5 - Connecticut, Illinois, New Jersey, New York and the Virgin Islands that cover public employees only. If you are working in one of those states or jurisdictions you should ensure that you are complying with their requirements
Cal OSHA has the “California Heat Illness Prevention Standard (GISO 3395),” which “applies to all outdoor places of employment.” (http://www.dir.ca.gov/title8/3395.html; http://www.dir.ca.gov/dosh/etools/08-006/index.htm; http://www.dir.ca.gov/dosh/etools/08-006/WhatIs.htm) Cal OSHA requires shade be provided when the temperature reaches 85 degrees Fahrenheit, but a worker may show signs of a heat-related illness at a lower temperature.
Minnesota OSHA has a more limited heat stress prevention regulation which only applies to indoor work spaces. (http://www.dli.mn.gov/OSHA/PDF/heat_stress_guide.pdf ) Minnesota Rules 5205.0110, subpart 2a and Appendix A (revised 1997), is the Minnesota OSHA standard for heat exposure. The standard is based on the wet bulb globe temperature (WBGT) and level of work activity. If the heat stress limit is approached or exceeded the following rules also apply: Employee Right-to-Know requirements specified in Minnesota Rules 5206.0700, subparts 1 and 3, “Training Program for Harmful Physical Agents;” and Minnesota Rules 5206.1100 “Labeling Harmful Physical Agents and Label Content.”
NIOSH has criteria for a recommended standard for “Exposures to Hot Environments,” which was revised in 1986 (http://www.cdc.gov/niosh/86-113.html.)
The international Standards Organization (ISO) provides guidance on heat stress (ISO 7933:2004 Ergonomics of the Thermal Environment).