Lightning is a dangerous natural phenomenon that can kill or severely injure outdoor workers, and is a major cause of storm-related deaths in the U.S. Lightning is a giant spark of electricity in the atmosphere within and between thunderstorm clouds (intra- and inter-cloud lightning) or between a cloud and the ground (cloud-to-ground lightning). Lightning can heat the air it passes through to 50,000 degrees Fahrenheit, which is five times hotter than the surface of the sun. During a storm, thunder is the acoustic shock wave from the electrical discharge of lightning. Therefore, thunder and lightning are associated with the other. Lightning is unpredictable and can strike outside of the heaviest rainfall areas or even up to 10 miles from any rainfall.
The frequency of lightning increases in the lower latitudes (closer to the equator) and higher altitudes (mountains). At any one time on Earth, there are 2,000 thunderstorms and 100 lightning strikes to Earth per second. The National Lightning Safety Institute (NLSI) reports that 1 out of every 200 houses in the U.S. will be struck by lightning per year, and the National Oceanic and Atmospheric Administration (NOAA) reports that the odds of a person being struck by lightning in the U.S. are 1 out of 1,222,000 in a year or 1 out of 15,300 in a lifetime of 80 years.
Annually in the U.S., cloud-to-ground lightning occurs 20 to 25 million times with over 300 people struck by lightning. From 1989 to 2018 in the U.S., about 43 people on average have been killed by lightning strikes annually with many more suffering permanent disabilities. More recently, in the last 10 years of record (2009-2018), the U.S. has averaged 27 lightning fatalities per year. NOAA reports that, based on 47 cases from 2006 through 2015, the highest percent of work-related lightning fatalities occurred in farming/ranching (34%) followed by “other” (23%), roofing (15%), construction (11%), and lawn care (9%).
Although the Occupational Safety and Health Administration (OSHA) currently does not have standards specific to lightning hazards, courts have interpreted OSHA's general duty clause to mean that an employer has a legal obligation to provide a workplace free of conditions or activities that either the employer or industry recognizes as hazardous and that cause, or are likely to cause, death or serious physical harm to employees when there is a feasible method to abate the hazard. This includes hazards related to lightning.
Although not specific to lightning, during storms or high winds, OSHA does prohibit:
- work on or from scaffolds (29 Code of Federal Regulations [CFR] 1926.451(f)(12));
- crane hoists (29 CFR 1926.1431(k)(8)); and
- work on top of walls (29 CFR 1926.854(c)).
In these situations, scaffold work may continue only if a qualified person determines it is safe and personal fall protection or wind screens are provided. Crane hoists may continue only if a qualified person determines it is safe.
Lightning should be recognized as an occupational hazard by employers and precautions should be taken to prevent or minimize exposure to lightning by workers. Outdoor workers who have a higher risk to lightning exposure include those who work in open spaces, on or near taller objects, or near explosives or conductive materials (i.e., metal). All employers, including workers and supervisors, should understand lightning characteristics and risks, and the precautions that should be taken to minimize potential exposure to lightning hazards. A Job Safety Analysis (JSA): also known as a Job Hazard Analysis (JHA), should be created to assess hazards; like lightning, while performing a task to determine controls and safe procedures to follow.
Many victims of lightning are caught outside in a storm because they did not act quickly enough to get to a safe place, or they returned outside too soon once the storm had passed. NO PLACE OUTSIDE IS SAFE DURING A THUNDERSTORM. Workers should not begin a task that they cannot quickly stop if a thunderstorm is approaching.
When working outdoors, proper planning and safe practices can easily increase safety from the hazards of lightning. OSHA and NOAA recommend that employers and supervisors follow these lightning safety best practices for employees working outdoors.
- Check NOAA Weather Reports: Before beginning outdoor work, NOAA weather reports and radio forecasts should be checked for all weather hazards for that day. Jobs should be considered for rescheduling if forecasts indicate the potential to be caught outside in hazardous weather conditions. Workers should continuously monitor weather conditions by watching for increasing wind speeds and darkening clouds, which are indicative of developing thunderstorms. Close attention should be paid to local television, radio, and Internet weather reports, forecasts, and emergency notifications on severe weather and thunderstorm activity.
- Seek Shelter in Buildings: Employers and supervisors should let workers know which buildings to go to after observing signs of an impending thunderstorm (lightning, thunder). NOAA recommends taking shelter in a fully enclosed building with electrical wiring and plumbing. Workers should remain in the building for at least 30 minutes after hearing the last clap of thunder or seeing the last flash of lightning.
- Seek Shelter in Vehicles: If safe building structures are not accessible, workers should take shelter in the nearest hard-topped vehicle with rolled up windows. Workers should remain in the vehicle for at least 30 minutes after hearing the last clap of thunder or seeing the last flash of lightning.
- Phone Safety: Except in an emergency, do not use corded phones after hearing thunder. Cell phones and cordless phones can be used safely.
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Prepare an Emergency Action Plan (EAP): As outlined in 29 CFR 1910.38 or
29 CFR 1926.35, employers should prepare a written EAP that includes
lightning safety protocol which should:
- Inform supervisors and workers to act after hearing thunder, seeing lightning, or noticing other warning signs of approaching thunderstorms.
- Indicate how workers are notified about lightning safety warnings.
- Identify locations and requirements for safe shelters.
- Indicate response times necessary for all workers to reach safe shelters.
- Specify approaches for determining when to suspend and resume outdoor work activities.
- Account for the time required to evacuate customers and members of the public, and the time needed for workers to reach safety.
Employers should adequately train all workers on lightning safety for each outdoor worksite, so that supervisors and workers know in advance where safe shelters are located and the time it takes to reach them. Employers should train supervisors and workers to provide lightning safety warnings in sufficient time for everyone to reach safe shelters and take other appropriate precautions.
An employer’s EAP may include lightning warning or detection systems, which can provide advance warning of lightning hazards. However, because no system can detect the “first strike,” detect all lightning, or predict lightning strikes, NOAA recommends that employers first rely on NOAA weather reports, including NOAA Weather Radio All Hazards.
If you find yourself caught outside during a thunderstorm, NOAA recommends the following to decrease the risk of being struck.
- Lightning is likely to strike the tallest objects in an area. Make sure that you are not the tallest object.
- Avoid isolated tall trees, hilltops, utility poles, cell phone towers, cranes, large equipment, ladders, scaffolding, or rooftops.
- Avoid open areas, such as fields. Never lie flat on the ground.
- Retreat to dense areas of smaller trees that are surrounded by larger trees, or retreat to low-lying areas (e.g., valleys, ditches) but watch for flooding.
- Avoid water, which is an excellent conductor of electricity, and immediately get out of and away from bodies of water (e.g., pools, ponds, lakes).
- Avoid wiring, plumbing, and fencing. Lightning can travel long distances through metal, which is an excellent conductor of electricity. Stay away from all metal objects, equipment, and surfaces that can conduct electricity.
- Do not shelter in sheds, pavilions, tents, or covered porches as they do not provide adequate protection from lightning.
- Seek fully enclosed, substantial buildings with wiring and plumbing. In modern buildings, the interior wiring and plumbing will act as an earth ground. A building is a safe shelter if you are not in contact with anything that can conduct electricity (e.g., electrical equipment or cords, plumbing fixtures, corded phones). Do not lean against concrete walls or floors (which may have metal bars inside).
If a worker is struck by lightning, apply cardiopulmonary resuscitation (CPR) immediately if the heart is in arrythmia or they are not breathing. People who have been struck by lightning do not carry an electrical charge and are safe to touch. Call 911 and promptly get emergency medical help.
A JSA worksheet or Activity Hazard Analysis (AHA) form can be created to determine the safety procedures when performing a task with the presence of lightning. JSABuilder.com is a fantastic on-line JHA software to assist in preparing your JSA or AHA. Set up a free trial account today and follow us on Twitter @JSABuilder, where we Tweet about Health and Safety, provide Safety tips, and updates on current Health and Safety topics.