Officials on Tuesday continued investigating the second round of illnesses in less than a week at a North Baltimore office building but did not quickly find a link between the two bouts.
Still, officials overseeing the investigation are confident that the building is safe and have decided it will be open for business on Wednesday.
The water heater that was identified as the source of last week's sicknesses — more than 20 people reported headaches, breathing problems and dizziness — was taken offline before the building, part of the Johns Hopkins at Keswick campus, was reopened.
But on Monday, about a dozen individuals reported symptoms similar to those experienced by employees last week and the building was again closed.
"To be absolutely clear, we are confident that water in the building is currently safe," said a statement Tuesday evening from Ronald R. Peterson, president of the Johns Hopkins Health System, and Daniel G. Ennis, a finance and administration executive for the Johns Hopkins University.
The heater was removed and replaced over the weekend, officials said. Kitchens, bathrooms and facilities connected to the heater that caused the illness — all on the north side of the campus' south building — have been closed since the first illnesses and will remain closed Wednesday, they said.
"Late [Monday], we learned that the nitrites that made employees sick last Tuesday were accidentally infused last Monday afternoon into the hot water heater serving the affected half of the south building," Peterson and Ennis said. "This knowledge corroborates our strong belief, based on hundreds of tests since last week, that this one hot water heater was the source of those illnesses."
Nitrites, a toxic substance that humans can be exposed to through ingestion, breathing or skin absorption, can cause shortness of breath, dizziness and, in extreme cases, coma or death. It is sometimes used to prevent steel corrosion in boiler systems.
"We have flushed the water in the system repeatedly. And we have tested the water repeatedly. The test results are negative," they said.
The water heater that was removed is estimated to be about 20 years old, said Dennis O'Shea, a spokesman for the Johns Hopkins University. Hopkins does not know the exact date of manufacture or installation, he said.
The heater was last inspected by the Maryland Department of Labor, Licensing and Regulation on July 11, 2011, he said. The inspection is valid for two years, O'Shea said.
"The precautionary closure of the Keswick south building on Tuesday has given us complete confidence that the building is safe for employees," Peterson and Ennis said.
Health department investigators "are continuing their epidemiological investigation of all the illnesses reported at Keswick, those from last week and those from Monday," they said.
Investigators are still trying to determine if the two incidents of sickness are connected, said Tiffany Thomas Smith, a spokeswoman for the Baltimore City Health Department.
Employees worked in the south building on Thursday and Friday last week and most of Monday morning before the second batch of illnesses were reported Monday. Throughout that time the contaminated water heater was out of the picture.
A fire official said Monday's patients were all light-headed and experiencing headaches, weakness, nausea and dizziness.
Although certain that the building is safe, Hopkins is taking extra steps to ensure its employees are comfortable when the building reopens Wednesday, officials said.
Water coolers, filled with water from outside the building, have been installed throughout the south building. An on-site doctor and nurse will also be present.
"We will continue to test water in the building on at least a weekly basis for the foreseeable future," Peterson and Ennis said Tuesday evening.
The contaminated water system will continue to be flushed and facilities that remain closed will be reopened after inspection by the Baltimore health department, they said.
The north building of the Keswick complex, on the eastern edge of Hampden by The Rotunda, is on a separate water systems, the officials said, and no illnesses have been reported there.
The two buildings house about 1,050 administrative workers from the university and health system. The south building was built in 1981.
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