“OSHA has refused to act on this for over 40 years,” Dr. Sammy Almashat, a researcher with Public Citizen’s Health Research Group, told EHS Today. “Twice, NIOSH recommended standards and one of those times, in 1972, OSHA convened an advisory committee which recommended a standard be adopted. I don’t know why OSHA refuses to act.”

According to Public Citizen, Farmworker Justice, the United Electrical, Radio and Machine Workers of America and Dr. Thomas Bernard, professor and chair of environmental and occupational health at the University of South Florida and a leading expert on heat stress in workers, at least 523 workers have died in the past 20 years and more than 43,000 have suffered heat-related injuries serious enough to result in at least 1 day away from work. However, because many worker injuries and deaths go unreported and many serious injuries are not counted in company data, even these numbers are probably a vast underestimate of the true scale of the problem, the groups said.

Excessive heat exposure while on the job can result in heat exhaustion, with symptoms such as nausea, headaches and extreme thirst, which, if not promptly treated, can progress to heat stroke and death. Workers are particularly susceptible to the effects of heat, in part, because certain types of clothing, such as personal protective equipment, block the normal sweat evaporation response, the body’s most critical cooling mechanism. The most vulnerable are agricultural workers – who account for more than one in five deaths resulting from environmental heat exposure – and construction workers, who suffer heat-related deaths at more than four times the national rate.

Almashat suggests that, “Agricultural workers, who are at the highest risk of heat-related illness, are more likely to be undocumented, and therefore less likely to speak out.”

Such workers also tend to not have representation through a union, except in California, one of three states to enact a heat-related regulation. “The United Farm Workers played a key role in the California standard in 2005 and 2006,” says Almashat. “In fact, they’re involved in a lawsuit because they claim the state is not enforcing the standard enough.” (The other two states with heat-related standards are Washington and Minnesota.)

This year, OSHA launched an educational campaign for employers and workers on the dangers of heat exposure, “Water Rest Shade,” but because it lacks an effective enforcement policy to hold employers accountable, this effort is doomed to fail, Public Citizen said in its petition.

When OSHA does address dangerously hot conditions for workers, it relies primarily on its indirect authority under the general duty clause. However, as Michaels noted several years ago before becoming OSHA administrator, the agency rarely exercises this authority and does so only in cases of egregious employer negligence. Over its 40-year history, OSHA has conducted just 112 inspections under the general duty clause in which citations were issued for violations of safe heat exposure practices, and 13 of those citations were later dismissed. By contrast, California, in the first half of 2011, conducted more inspections related to hot conditions for workers than OSHA has in 40 years.

“OSHA has demonstrated an alarming lack of oversight over the past 40 years in the face of this recognized and entirely preventable hazard,” said Dr. Sidney Wolfe, director of Public Citizen’s Health Research Group. “Only with the implementation of a specific, enforceable standard will hundreds of lives be saved and thousands of heat injuries prevented over the next decade.”

Public Citizen and the other groups are calling on OSHA to implement a permanent heat standard that would apply to all indoor and outdoor workers. The agency should require that workers have access to sufficient drinking water and shade, and be given mandatory rest breaks on particularly hot days, among other measures.

“There would be some economic impact on business from a mandatory standard,” says Almashat, “but it would save lives. “ As a result of a lack of a standard, “tens of thousands of workers have suffered serious injury or death while OSHA essentially relies on employers to police themselves,” he adds.

“OSHA has just received the petition and is reviewing it,” said a statement from the agency.

“This spring, in an effort to combat work related heat fatalities and thousands of heat-related illnesses each year, OSHA launched a nationwide outreach campaign to help educate workers and employers on the hazards of working outdoors in the heat and the steps needed to prevent heat illness,” the statement continued. “The campaign includes major outreach efforts by OSHA and its state partners, new low literacy materials in English and Spanish, a new web page, training tools for employers and community organizations, posters and additional educational resources. A mobile phone app was also created to enable workers and supervisors to calculate the heat index and protective measures necessary for their worksites. OSHA continues to work diligently to ensure the safety of workers at risk of heat illness.”