The Hidden Danger When Buying Antique Clocks, Watches, Barometers and Thermometers

Recently I visited the beautiful market town of Hawes in the Yorkshire Dales in Northern England and was delighted to come across an antique shop which specializes in antique clocks, watches, barometers and thermometers. All their antique clocks, watches, barometers and thermometers were carefully restored and sold with a guarantee.  The wonderful array of products on display looked like brand new. I was very excited about the collection.

This antique shop is a family run business established nearly 30 years ago who have always prided themselves in providing customers with a fantastic choice of quality original antiques at competitive prices. Their display of superb long-case, bracket, grand-father and mantle clocks was fantastic and they seemed to have one of the largest choices of barometers and thermometers I have ever seen.

But herein lies the hidden danger associated with antique clocks, watches, barometers and thermometers A large proportion of the antique thermometers on display were mercury thermometers. As a professional Microbiologist I immediately became concerned especially when the person I was with chose an elaborate Antique clock with a barometer and a mercury thermometer barometer and wanted to carry it with him as hand luggage on our flight back to Sydney, Australia.

 

Neither my friend nor the owner of the shop seemed to be aware of the dangers of mercury. Mercury is a heavy metal with the chemical formula Hg and is highly toxic and corrosive. Mercury poisoning include damage to the brain, kidneys and lungs resulting in several diseases including acrodynia, Hunter-Russell syndrome and Minamata disease. 

In mercury thermometers it is used in its liquid form. Mercury is a shiny, silver-white metal that is liquid at room temperature. The glass mercury thermometer consists of a large bulb containing the liquid mercury which is attached to a glass tube of narrow diameter. Therefore the volume of mercury in the tube is much less than the volume in the bulb. The volume of mercury changes slightly with temperature and this small change in volume drives the narrow mercury column a relatively long way up the tube.

Whilst it is encased in the glass it is quite safe. However the glass bulb and tube are very fragile and easily subject to breakage and obviously if broken the mercury is released. The liquid metallic mercury or quicksilver as it is commonly known is poorly absorbed by ingestion and skin contact but it is hazardous due to its potential to release mercury vapor. If not sealed off, mercury slowly evaporates into the air, forming a vapor. The quantity of vapor formed increases as temperatures rise.

In humans, approximately 80% of inhaled mercury vapor is absorbed via the respiratory tract from where it enters the circulatory system and is then distributed throughout the body. In trials it has been proven that chronic exposure by inhalation, even at really low concentrations can cause effects such as tremors, impaired cognitive skills, and sleep disturbance. Acute inhalation of high concentrations causes a wide variety of cognitive, personality, sensory, and motor disturbances.

 Toxic effects of mercury may also be caused by things like amalgam fillings and mercuric salts which contaminate certain fish species. Mercury occurs inorganically as salts such as Mercuric Chloride. Mercury salts affect primarily the gastrointestinal tract and the kidneys causing severe kidney damage.   However, as they cannot cross the blood-brain barrier so they do not usually cause neurological damage without continuous or heavy.

Mercury is listed as a corrosive by the US Dept. of Transportation and must be shipped as a hazardous substance. So simply carrying a mercury thermometer as part of your hand luggage is not allowed internationally or domestically and there are strict regulations about how it can be transported or posted. You need to contact your local authority before purchasing, posting or receiving a mercury thermometer. 

In 2012^[update], many mercury-in-glass thermometers were used in the sciences such as meteorology and microbiology. They were also really common in medical “fever” thermometers and antique wall thermometers such as the ones I saw in this antique store.  However they are being phased out and are becoming increasingly rare. Many countries have banned them for medical use due to the toxicity of mercury. Some manufacturers use alcohol, galinstan, a liquid alloy of gallium and indium, or tin as a replacement for mercury.

Mercury poisoning can be prevented or minimized by eliminating or reducing exposure to mercury and mercury compounds. To that end, many governments and private groups have made efforts to regulate heavily the use of mercury, or to issue advisories about its use. Many countries have regulations or recommendations on the selling and use of mercury thermometers. For example the UK where these mercury thermometers were on sale follows the European Union directive 2007/51/EC on mercury thermometers which came into force on 3 April 2009.  

The UK Health Protection Agency  (HPA) reported that mercury thermometers could no longer be sold to the public. Shops holding stocks of unsold thermometers had to withdraw them from sale but that mercury thermometers purchased before this date could be used without legal implications. The purpose of these restrictions is to protect the environment and public health by decreasing the amount of mercury waste released. The USA Environmental Protection Agency recommend that alternative thermometers be used in the home.

The export from the European Union of mercury and some mercury compounds has been prohibited since 15 March2010.  However the variability among regulations and advisories is at times confusing for the lay person as well as scientists.

 Previously in 2007, the HPA had released a guide to dealing with small spills of mercury, and it is my advice that anyone with a mercury thermometer in their home should read these guidelines and purchase a mercury spill kit and learn the safe way to deal with a mercury spill.

So if you intend to buy an  antique clocks, watches or barometers with an attached mercury  thermometers beware of the hidden danger of mercury and only choose a thermometer if it is alcohol based.