That thermometer, which even children know how to use, can be a health hazard if not handled with care, says a study.
And guess who are most careless while using it: hospital employees, according to the study by Delhi-based NGO Toxics Link.
On average, 70 thermometers break every month at each of the more than 300-bed hospitals in the city, the study says, sending mercury vapours into the air, which when inhaled causes a host of long-term damage to the body like retarding the nervous system and damaging the kidneys.
Mercury is the only heavy metal that evaporates even in room temperature and Prashant Pastore, who co-wrote the study, says no level of the metal in the air is good for the human body.
The study found the air inside two prominent private hospitals heavy with mercury, higher than what is allowed by international standards.
The NGO did not wish the names of the two hospitals — one in west Delhi and the other in north — published, saying both had initiated "responsible mercury management programmes".
One of these hospitals employs up to 3,000 medical and non-medical workers.
"This makes the staff and patients at such hospitals unsuspecting victims of such contamination. In India, we are yet to have a standard on mercury for the healthcare sector, where the metal is extensively used," said Ravi Agarwal, director of Toxics Link, on Wednesday while releasing the study: 'Mercury in Hospital Indoor Air: Staff and Patients at Risk'.
Not just thermometers, a host of hospital instruments uses mercury: for example, blood pressure-measuring instruments and fluorescent lights.
The study found dangerous levels of mercury in all departments at these two hospitals — general wards, nursing stations and storerooms.
In one hospital, the air in the room for nurses had an average mercury concentration of 1.98 micrograms per cubic metre, much higher than the US permissible limit of 0.3 micrograms per cubic metre. The air in the storeroom of the other hospital was worse with mercury presence at 3.78 micrograms per cubic metre, levels considered perilous.
"Mercury presence in the dental room (where mercury is extensively used as tooth fillings) was 3.11 micrograms per cubic metre," said Pastore.
The study also examined hairs of 10 nurses and doctors working at these hospitals and found high levels of mercury in them.
The NGO sent the results of these samples to a larger study of 266 similar samples from 21 countries. "More than 94 per cent of the samples were found contaminated," Pastore said.
Responding to the study, medical officer of Centre for Environment and Occupational Health Dr Neeraj Gupta told the HT mercury posed a health as well as occupational hazard in the health sector. "Apart from the nervous system, it also affects the kidney and has been found to cause autism."