The amounts found by an expert team far exceed the limits issued by the environmental agency. The source of the mercury contamination is named as the drainage system, according to the report. The report also states that „mitigation measures are necessary“.

The university decided that business can be conducted as usual, with some restrictions. Former employees and students who were exposed to the mercury fumes, possibly for years, were not specifically informed yet about the extent of the contamination.

Decontaminating the protected building would incurvery high costs, according to the experts.

If there hadn’t been a mishap, the mercury contamination in the air might have never been detected. In spring this year, a measuring instrument in the cellar broke, releasing some of the poisonous heavy metal in to the air. After the mercury was removed, experts measured the levels in the air as a routine check - and noticed something they could not quite explain at first. Not only the room in question but also the halls, other rooms and other storeys as well as the lecture halls were affected.

In total, 147 rooms, including three lecture halls, are contaminated.

Heinz-Jörn Moriske, who is leading the counselling centre for environmental hygiene at the federal environmental agency, saw it as the university’s duty to act immediataley. The agency is not responsible for this case, but was asked by the General-Anzeiger for a professional judgement on the measured mercury levels. Moriske: „Nobody should be allowed to sit anymore in some offices.“

Until 1972, the complex was used intensively by the chemistry faculty, after that it was empty and decayed. 1984 the city listed it as a protected building, for three years, extensive restoration works were undertaken. After that the geographers moved in, then the microbiologists. Since then the scientists are not using chemicals like mercury there any more. Obviously the old, contaminated drainage pipes were not exchanged - which, according to Moriske, should have been done to remove the mercury sources. „If the drainage system is indeed the ‚culrpit‘, it most likely has to be taken out.“ Experts suggest to examine the pipes from the inside with cameras, and to clean them.

The university has decided on utilisation periods as a first measure, and hung up notifications on many doors. Five rooms are allowed to be used for one hour per day, another nine rooms for up to four hours. Two rooms are completely sealed off. Pregnant women are not allowed into the lower storeys of the building complex any more. In a information event in September, some employees and students were told of the new regulations. And there was a notification on the university’s website.

The exact levels were not published, according to the students and staff. They were told instead to open the windows. „Very strict limits“ were set in the examinations, they were told.

University spokesperson Andreas Archut also doesn’t call the contamination „alarming“. he argues that the measuring took place with closed windows and switched off air-conditions - a scenario indicating the worst case. The levels measured were ranging from „extremely elevated to extremely low“.

But only the labs have air-conditioning systems which are running around-the-clock. It is quite unlikely that the windows in the other rooms are open all the time. „We assume there is no danger if the agreed utilisation periods are respected, which were established with the in-house medical authority“, said Archut.

So far, only „very few“ people had presented themselves at the university’s doctors’ offices. „There were no complaints about health problems.“ It remains unclear though what happened to the hundreds of students and employees who were exposed to the fumes since the geographers moved in in 1987.

According to Archut, the cause of the contamination is not clear and can „possibly be traced back to the 100-year long use of the building as a chemical institute“. The expert report names a definite result: „The sources are, according to the first measurings, the drainage pipes.“ Not only inside the building, but also in exterior gullys, for example in the inner yard, there were mercury amounts found. From there, the waste water runs into the sewer system. The report is substantiated by the reports of former institute staff: Mercury used to be poured straight down the drain back then, they told the GA newspaper. Therefore the contamination would be so high in basin and floor drains.

The city council Bonn was not officially informed about the incident, according to the press office. „We assume these findings are an internal issue for the university, where occupational safety and in-house doctors are in demand“, said a city council spokesperson.

The NRW ministry for culture and science as well as the construction and the building and infrastructure service NRW (BLB) who rents the building to the university have been notified. „The university uses the complex independently and is responsible for the facilities and technical systems itself“, said BLB spokesperson Tim Irion. Thus the university has to handle the incident and has to call the experts in itself.

To measuremercury fumes in room air there are the guide values I and II of the environmental agency: guide value I (35 nanogram per cubic meter room air) describes a so-called precautionary value, within which no health risks are expected even if lifelong exposure occurs. Guide value II or „risk value" is an amount coinciding with health risks. It is describing a concentration of a a subtance which is so high that an immediate reaction is called for. In particular to permanently stay in the rooms affected can be dangerous to sensitive people including children.

Workplaces like labs for example have specific level limits. For mercury those levels are at 20,000 nanogram per cubic meter of room air. (Original text: Nicolas Ottersbach, Translation: Mareike Graepel)