“The not using the restroom thing was really the last straw for me,” said Vivian Valadez, 36, after working for less than three months for Sanderson Farms, the third largest poultry provider in the United States.

With only two scheduled breaks per eight-hour shift, Valadez explained how a handful of workers in her area had invented “their own little restroom schedule” to relieve themselves outside official break time. They took it in turns to stand in for each other, while “trying to hurry up” to limit the effect on the rest of the poultry line.

One day Valadez got reprimanded by a supervisor on her way back from the bathroom. Even though she claims her own manager “was never really around”, the supervisor told Vivian she had to “wait until he came back around” to ask for his permission.

In an interview with the Guardian, a former Sanderson Farms supervisor, who asked to remain anonymous, described how she and her peers were encouraged to ignore worker requests for bathroom breaks.

“A superintendent would sometimes tell us to leave the area when workers were likely to go to the restroom. That way they couldn’t ask us for permission to go,” she said. “So at times we would remove ourselves from the area,” said the employee.

Valadez left the processing plant in Bryan, Texas in 2016. But workers today say conditions haven’t improved. Two years later, she still remembers the incident that led to her resignation. “Nobody is going to tell me when I can and can’t go to the restroom. So I didn’t go back after that,” she said.

As a former worker and a US citizen who is not the family breadwinner, Valadez was more willing than others to speak publicly about her experience. Poultry processing mainly attracts unskilled immigrant workers, African Americans, single mothers or even felons who are more vulnerable and fear employer retaliation.

The poultry industry “has created a culture to keep people living in fear,” said Brandon Hopkins of the United Food and Commercial Workers Union (UFCW) who represents workers at Sanderson Farms as well as other poultry giants including JBS and Pilgrim’s Pride.

In his 10 years as a union representative in Texas and Louisiana, he says he has “had employees go to the bathroom on themselves because they are so scared of getting in trouble that they don’t leave the line”.

The bathroom access problem is industry-wide but Sanderson Farms executives emphatically deny it affects their employees. “That would be a violation of our policies,” said Mike Cockrell, chief financial officer and spokesman for the company. “Any supervisor who was found to have done that would be terminated immediately,” he added.

But current employees claim that any restroom request outside the authorized 12-minute break and 30-minute unpaid lunch break is at the supervisor’s discretion.

“I tried not to drink water because I knew my supervisor wasn’t going to let me go. Not even if I was peeing on myself,” said one worker who had worked at Sanderson Farms.

A former supervisor claimed pressure from her own managers to turn out more chicken was immense. “I say I’m a supervisor but I’m really just doing what I’m told,” she said. “And I get into trouble if I don’t.”

Having started off as a worker herself, she experienced firsthand the humiliation of having a bathroom request denied. “The workers complain a lot and I understand. Sometimes they have to wait 30 or 40 minutes and they won’t let them use the restroom.”

“Sometimes they make you wait so long that you don’t want to go any longer,” she added.

That is not the only problem. The plant employs 1,400 workers and restrooms are located far from workstations. “If I run, I can get there in three minutes,” said one employee. “But if I go at a regular pace it takes me four or five.”

“I know because I’ve timed myself,” she said.

“So the 12-minute break is really only eight,” added another.

Cockrell did concede that the issue of bathroom breaks had been brought to his attention. “That allegation has been raised from time to time, particularly by labor unions during negotiations. But we categorically deny that. It would be a violation not only of our policies and OSHA [Occupational Safety and Health Administration standards] but of basic human dignity,” he said.

The UFCW’s Brandon Hopkins disagreed: “Sanderson Farms’ answer is that any time anybody wants to use the bathroom, they can. We both know that is not true.”

Conditions across the poultry industry are notorious for high turnover rates. Others argue that employees should be grateful for the job. “With no skills they are making $12.50 an hour,” said Brodrick Ross, a workforce specialist at the state-run Texas Workforce Commission, that acts as a first point of contact for low-skilled workers looking for employment.

According to documents seen by the Guardian, the entry-level wage – which includes a competitive benefits package – is $12.20 per hour and rises to $13.55 after a year on the job. Workers say it’s the highest-paying job in the area.

OSHA inspected the Sanderson Farms plant in Bryan in June and again in September after a complaint was filed by the Centro de Derechos Laborales, a local group that advocates for Hispanic worker rights. The government body has six months to investigate.

One employee from Mexico noticed that conditions improve drastically during OSHA visits. “Today was unusual,” she said. “They gave us three breaks instead of two.”

“We stopped work at 4.30pm and they gave us a break at 3.15pm. I wonder if it has anything to do with the fact that OSHA came.”

A former supervisor also noticed that working conditions were significantly better whenever there was an inspection. “They put less chicken on the line. Everything looks slower and people look more relaxed, ” she said.

OSHA issued its first citation against a company for violating a worker’s right to use the restroom in 1997. For Debbie Berkowitz a lifelong workers’ advocate, currently at the National Employment Law Project (NELP) in Washington, DC, this was a watershed moment. But for many poultry workers across the United States, over 20 years later, the issue is still unresolved.

OSHA standards state that employees should be able to use the restroom whenever they need to – within reason.

“If they are on the line, and they need to go to the bathroom, they shouldn’t have to wait longer than 15 minutes or so,” said Berkowitz.

Labor laws also make clear that lack of bathroom access is a health risk. Pregnant women, the elderly, and people with medical conditions that cause them to urinate more often are particularly vulnerable.

Pedro Guerrero, a worker with diabetes who left the Sanderson Farms plant in 2012 after hanging chickens on the line for two years remembers the time his manager confronted him for going to the bathroom. “My supervisor asked me where I was going,” Guerrero recalls. “Can’t you wait until the break?” he said. “Do you want me to do it in my pants?” replied Guerrero, pulling on his pants zipper.

The 60-year-old worker from the Mexican state of Jalisco who became a US citizen over 20 years ago, harbors bitter memories over the discrimination he suffered at the plant. He claims that US-born workers would regularly go to the restroom “to text or fool around”, while he was verbally harassed by his manager.

Experts say restricted bathroom access disproportionately affects women due to urinary tract infections, menstruation and pregnancy. Earlier this year, the Southern Poverty Law Center filed complaints against Case Farms in North Carolina and Fieldale Farms in Georgia alleging sexual discrimination for restricted bathroom access for two female poultry plant workers.

At Sanderson Farms, a current employee showed me a doctor’s note asking her supervisor to let her use the restroom as needed. “We would ask permission to use the restroom. They would ask us to wait. And then sometimes they would forget,” she said.

An Oxfam report from 2015 and a Government Accountability Office study from 2017 confirm that lack of bathroom access runs across the poultry industry.

Labor experts link the issue to a push for increased productivity and increased line speeds following a rise in consumer demand for chicken in the 80s and 90s.

More specifically they say the issue is symptomatic of the industry’s high turnover rate. “It’s about staffing. They don’t have enough staff to replace a worker who needs to go to the bathroom,” said Berkowitz.

Employees complain of the line speed interfering with their ability to take breaks. One worker, who resigned this summer and now works at a local bank, tearfully recalled how, as a newly arrived untrained worker at Sanderson Farms, she was put under intolerable pressure by her supervisor to “pack 60 chicken drumsticks per minute”. She was later told by another supervisor that “the requirement was 45”.

In a recent move, the US Department of Agriculture (USDA) announced that it was allowing poultry processing plants that meet certain criteria to increase their line speed even further.

The overall line speed at Sanderson Farms in Bryan, Texas, is a well-kept secret. But union representatives think the plant already runs “one of the faster lines in the industry”.

“It’s hard,” says Vivian Valadez, thinking of her former colleagues. “It’s hard for them. I’m not there any more.”

• Reporting for this story was supported by the International Women’s Media Foundation (IWMF).