They say the government has turned their back on him.

Friends of Rafael Hernández, an undocumented Mexican firefighter who volunteered at ground zero after 9/11, then years later became ill and died, are questioning the medical examiner’s conclusion on the cause of his death.

The ME’s office said Hernández, who emerged as an advocate for immigrants exposed to thick layers of dust at ground zero, died of natural causes.  

Hernández, 49, died Sept. 25 of obesity with obstructive sleep apnea and cardiac enlargement, said the city's medical examiner's spokeswoman, Ellen Borakove. Hernández also suffered from an acute and chronic alcohol abuse, she said.

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"The government has turned its back on him," said Jaime Munevar, a Colombian immigrant who says he is also sick from his cleanup work at ground zero. "He told me before he died how much his back and lungs hurt. The pain is common among us, the immigrants who worked in the area."

Hernández, who came to the U.S. illegally in 1999, died in his Queens apartment. He held a biweekly support group for other immigrants with illnesses they believed were related to their work at ground zero. Many of them expressed dismay that the death of Hernández was not officially linked to his exposure to the clouds of dust at the disaster site a finding they believe may have strengthened his claim for victims' medical compensation. His name would have been placed on the memorial to 9/11 victims that now sits at the World Trade Center site.

Thousands of people have blamed health problems on trade center dust, but evidence linking deaths to the dust has been inconclusive. The New York City medical examiner's office rarely categorizes deaths as related to the toxic dust.

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Hernández had been diagnosed with respiratory problems after 9/11 and often went to a hospital. Obesity is a common cause of sleep apnea and cardiac enlargement.

Weeks before his death, Hernández told Fox News Latino he rescued people from the Twin Towers on Sept. 11 and even carried a pregnant woman down 28 flights of stairs. Then he spent days searching for survivors, and then months trying to clean up the wreckage at Ground Zero – but was only given a flimsy mask to protect him against the toxic fumes billowing from the disaster.

This has stained his legacy. Rafael used to say that if one day he was no longer around, we needed to keep fighting for compensation.

- Rosa Duque, a Guatemalan immigrant who knew Hernandez.

Eventually, he said, he started feeling weak.

“Now I walk like an 80-year-old man,” Hernández says. “I take a few steps, and I have to stop to catch my breath. I walk up steps from the subway to the street, and I feel exhausted.”

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His lawyer, Jorge Anzola, said Hernández settled a lawsuit against the city in 2010 over the disaster cleanup work done without adequate protective gear.

"Rafael was a wonderful person. He did a lot for a lot of people," Anzola said. "But he was sick. He was on the go all the time, and I told him he had to take care of himself."

Hernández also suffered from asthma and slept with a machine to aid his breathing.  Consuelo Trujillo, a Colombian immigrant who also suffers respiratory problems, said she blamed on her cleanup work at ground zero.

"He would suffocate when he talked and he had to stop for a second, to breathe," Trujillo said.

New York City's Hispanic community has reacted negatively to the medical examiner's decision, said Rosa Duque, a Guatemalan immigrant who knew Hernández.

"This has stained his legacy," the former cleanup worker said. "Rafael used to say that if one day he was no longer around, we needed to keep fighting for compensation."

Hernández led a biweekly support group called Frontiers of Hope where the workers discussed their illnesses. They also sought to cope with the long-term psychological effects of their time near the disaster site.

Before he died, he was expecting to receive his last check from the city and then move back to Mexico to be with his family, Anzola said.

He visited Ground Zero for the last time with Fox News Latino a few weeks before his death. He did not want to attend 9/11 anniversary events, but wanted to visit the site one more time before he left the country for good, he told Fox News Latino.

"It hurts too much to be here, to be immersed in it,” he said. “I’m not September 11. I want to bury it, move on. I will not come back here ever again.”

He stayed true to his promise.

Though the number of Hispanics who were part of the ground zero cleanup crews is unknown, leaders of the immigrant community agree that Hispanics represented a large percentage of cleanup workers. Many were in this country illegally, they say, and contractors normally did not ask them for immigration papers, paying them low wages, in cash.

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Before Sept. 11, Hernández worked at a Queens shop, his friends said. As a professional paramedic firefighter in Mexico, he worked for the Red Cross there until he moved to New York in 1999, leaving behind two daughters and one son. He became a volunteer firefighter for the city fire department.

"I am not surprised by the medical examiner's decision but I feel he did not receive the medical help he needed," said Brenda Olvera, his wife, who lives in Mexico.

The medical examiner's conclusion does not change anything, Anzola said. Hernández's family will receive his last city check and hope to benefit from a fund to compensate people who might have been sickened by exposure to trade center dust and ash.

Hernández's body was sent to Mexico for cremation but his organs stayed in New York to be analyzed by the medical examiner, his family said. During his wake in the fall, dozens of immigrants gave emotional speeches and paid tribute in song.

"He was deteriorating fast," said Virginia Villa, 63, a Colombian immigrant who said she also was sickened by the 9/11 cleanup work. "I am worried about this medical conclusion because we are in the same situation. This is not dying by natural causes."

Based on reporting by The Associated Press.

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