A US congressman will go without food and water in a protest over a Texas law overriding protection for people working outdoors in intense heat.
Representative Greg Casar, a Democrat, says the “thirst strike” will go on until a nurse requires him to stop.
It comes ahead of the Texas rule change and as temperatures soar across vast swathes of the southern and western US.
The new Texas law effectively bans local rules, such as a 10-minute break for every four hours worked outside.
More than 400 workers have died in heatwaves since 2011, according to Bureau of Labour statistics.
Mr Casar said in a tweet that he plans on “not drinking water or taking breaks, through rain or shine, in solidarity with our nation’s workers”.
“Currently, there are no federal protections for workers exposed to heat,” he added.
As he began his thirst strike at the US Capitol, Washington DC was experiencing hot, humid temperature of about 31C (87F). Without fluids, a human can only survive a few days, according to the UK National Health Service.
In a letter, Mr Casar and more than 100 other members of Congress said protection from extreme heat “is a matter of life and death for many workers and their families” across the US.
It cited a report of several examples of workplace deaths to have taken place this year that are believed to be the result of the heat.
The death of a 40-year-old postal worker who died on his route and a 35-year-old worker believed to have died of heat exhaustion while working to restore power in Texas’ Harrison County were included.
“We know extreme weather events such as heat waves are becoming more frequent and more dangerous due to climate change,” the letter added. “Urgent action is needed to prevent more deaths”.
The letter called on the federal government to implement a number of safeguards.
Texas Governor Greg Abbott signed a law overturning several local heat protections, such as an Austin regulation requiring a 10-minute break for every four hours for people working in the heat.
Supporters of the Texas move argued local regulations were applied “inconsistently” and encroached on the state’s ability to regulate commerce and trade.
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“Our nation – and my home state of Texas – is experiencing a historic heatwave – exposing workers to deadly 100+ temperatures,” Mr Casar tweeted.
“Yet in the middle of the heat wave, Greg Abbott signed a law eliminating workers rights to water breaks”.
Absent any federal policy, the Texas law goes into effect on 1 September.
The current intense heat for much of the US shows little sign of abating. About 46 million Americans were under heat warnings on Tuesday, with temperatures expected to rise for many parts in the coming days.