The glass thermometer that we have been putting in our mouths for so many years contains the most lethal of ingredients that can pose serious health problems if accidentally spilt.
Mercury spilling on the ground due to accidental breakage of thermometers is fairly common in big hospitals, and sometimes in homes too, but this seemingly innocuous happening can expose humans to severe poisoning effects of the silvery liquid-like metal.
Mercury readily turns into vapour at room temperature and when inhaled gets absorbed into the bloodstream and attacks the nervous system. Even physical contact with the liquid, which is easily absorbed through the skin, is dangerous as some of it passes through the skin into the bloodstream, leading to tremors, nausea and blurred vision.
Given its risks, the West has stopped the use of mercury in thermometers, but they continue to be commonly used in India. There is also no awareness about the dangers posed by mercury poisoning or the need for careful handling of thermometers.
"India is the second largest user of mercury - we import 200 tonnes every year. It is imported from many parts of the world including Europe. India doesn't mine it. Mercury escapes into the air and water, and from water into fish. We don't have any regulation even on trade in mercury. It is freely available in chemical markets, even in Delhi," said Ravi Agarwal, head of the Delhi-based environmental group Toxics Link.
"When a mercury thermometer breaks, the mercury spilled starts vaporising immediately in temperatures of 22-24 degrees Celsius. The vapours can be inhaled by anyone in the vicinity. It goes straight into the lungs and into the blood and the brain. It is very dangerous.
"In India, there is no awareness or precaution observed. In the West when a thermometer broke, they would close the room for two-three days and clean the place thoroughly," Agarwal said.
"All over the world they have stopped using mercury and use only digital thermometers."
Asked what the proper procedure would be to clean spilled mercury, Agarwal said a syringe should be used to suck up the liquid under water, maintaining great care all the while.
"Just one gram of mercury is enough to contaminate a 20-acre lake and make the fish unfit for eating. That is the kind of toxicity of mercury. It is also very dangerous when people play with it, thinking it to be just a silver ball. It is absorbed into the skin and the blood," said Agarwal, whose organisation will join a large number of NGOs at the 24th United Nations Environment Programme (UNEP) Governing Council meeting from February 5-9 in Nairobi to urge governments across the globe for a ban on mercury exports.
One of the key demands will be to call upon developed nations to provide new and additional funding towards mercury reduction in developing countries.
"We are pressuring the government and working with hospitals to switch over from mercury-based thermometers. Some hospitals in Delhi have already started using non-mercury thermometers."
A branded mercury thermometer costs around Rs 100, though cheaper ones are available that are prone to breaking or leakages. On the other hand, a branded digital thermometer costs around Rs 250, but there are cheaper models too.
Mercury is a neurotoxin, meaning it attacks the nervous system and brain. In small children, mercury poisoning has been linked to birth defects, learning disabilities, walking and talking delays and memory or attention problems.
In adults, mercury poisoning leads to tremors, headaches, blurred vision, memory or concentration loss, hand and feet numbness, poor coordination, hair loss and nausea.
In extreme cases, mercury poisoning can lead to coma and death. However, the symptoms of mercury poisoning can be reversed in adults. It takes about six months to a year for the body to naturally remove mercury once the exposure stops. Some researchers believe that mercury can permanently damage children's nervous systems.
In a recent study, Toxics Link pointed out that mercury poisoning posed an occupational hazard to medical staff and the community at large, including young children and pregnant women.
Its findings from tests conducted at hospitals revealed that the metal was present in amounts far exceeding the prescribed limits.
Prashant Pastore, lead investigator of the study, said in his report that around 70 thermometer breakages occur every month in 300 to 500 bedded hospitals. And, on an average, a hospital pumps almost three kg of mercury in environment each year.