An official with Red Cross Hospital in Kumamoto said the 34-year-old man later died while the people who were sickened were "progressing favorably."
Eleven of the 54 people who were sickened were doctors; another 20 were staffers at the hospital in the city of Kumamoto.
The liquid pesticide the man consumed was later identified as chloropicrin, which was used to produce tear gas during World War I and induces tears and vomiting.
|Japan has had a spate of suicides including this one in Konan, where a 14-year-old girl died in April.|
"It took a long time to determine the kind of chemical," said the doctor who treated the man in the emergency room.
The hospital's emergency center was closed for about 12 hours after the incident.
The man's death is the latest in a spate of toxic fume suicides that have hit Japan in the last month.
Earlier this month, a 24-year-old man killed himself by mixing laundry detergent and cleaning fluids, releasing noxious fumes into the air that forced the evacuation of hundreds of people. His mother also fell unconscious after inhaling the fumes.
In April, 14-year-old girl killed herself using the same method. Ninety neighbors were sickened by fumes and had to be treated in the incident in southwestern Japan.
In the week the girl died, a 31-year-old man outside Tokyo killed himself inside a car by mixing detergent and bath salts, police said.
The suicides are seen as part of a spate of detergent-related deaths that experts say have been encouraged by Internet suicide sites since last summer.
Seiji Yoshikawa, deputy head of the Internet Hot Line, which operates under the guidelines of police, said the number of sites promoting detergent suicides soared in April.
"They are rife on the Internet. Writing examples include 'you can die easily and beautifully' and 'this is much easier than charcoal-burning suicide," Yoshikawa said, referring to a once-popular suicide method, The Associated Press reported.
Japan's government has long battled to contain the country's alarmingly high suicide rate.
A total of 32,155 people killed themselves in 2006, giving the country the ninth highest rate in the world, according to the government.
Suicides first passed the 30,000 mark in 1998, near the height of an economic slump that left many bankrupt, jobless and desperate.
The government has earmarked 22.5 billion yen ($220 million) for anti-suicide programs to help those with depression and other mental conditions.