Mercury is used in many measuring devices mainly in hospitals, clinics and doctors’ offices but also for in other measuring and control equipment.
Mercury is contained in many common medical measuring devices: sphygmomanometers (blood pressure devices), thermometers (specifically body temperature thermometers but also others) and a number of gastro-intestinal devices, such as cantor tubes, esophageal dilators (bougie tubes), feeding tubes and Miller Abbott tubes.
As in other types of instruments, mercury has traditionally been used in these devices because of its unique physical properties, including the ability to provide highly precise measurements. These instruments include barometers, manometers, but also porosimeters, pycnometers, hygrometers, tensiometers, gyrocompasses, mercury-containing reference electrodes, hanging drop mercury electrodes, gas flow meters, and coulter counters among others.
Relevant legislation and NGO policy work
The Minamata Convention on Mercury, under Article 4 requires that Each Party shall not allow, by taking appropriate measures, the manufacture, import or export of the following mercury-addednon-electronic measuring devices except non-electronic measuring devices installed in large-scale equipment or those used for high precision measurement, where no suitable mercury-free alternative is available: (a) barometers; (b) hygrometers; (c) manometers; (d) thermometers; (e) sphygmomanometers, after 2020, except where the Party has a registered exemption pursuant to Article 6.
Health Care Without Harm (HCWH) has been working globally to promote mercury free hospitals. HCWH and the World Health Organization are co-leading a global initiative - Mercury Free Healthcare to achieve virtual elimination of mercury-based thermometers and sphygmomanometers over the next decade and their substitution with accurate, economically viable alternatives. The initiative is a component of the UN Environment Programme's Mercury Products Partnership.
In the EU
The restriction of measuring devices as below for professional use and in healthcare, together with the initial restrictions for consumers are incorporated under the EU Chemicals regulation REACH.
The export of these products is banned after 2020, by the 2017 EU Mercury regulation.
Following the 2005 EU Strategy on Mercury, includingan action (Action 7) in view of restricting the marketing for consumer use and healthcare of nonelectrical or electronic measuring and control equipment containing mercury, Directive 2007/51/EC, was published on 2 October 2007 in the Official Journal of the European Union. It prohibits the placing on the market of all mercury fever thermometers (for consumer and professional use), and for all other measuring devices intended for sale to the general public (e.g. manometers, barometers, sphygmomanometers, thermometers other than fever thermometers). It came into force on 3 April 2009.
The NGO activities and follow up of this issue are presented here in chronological order.
In October 2009, Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) published their Opinion on: Mercury Sphygmomanometers in Healthcare and the Feasibility of Alternatives.
Beyond the above restriction, the EC prepared a report with all relevant elements concerning potential restrictions in the use of mercury in measuring devices for professional use and in healthcare (e.g. sphygmomanometers in hospitals/clinics, porosimeters etc) which was sent this to the European Chemicals Agency (ECHA).
The Risk Assessment and Socio-economic Analysis Committees of ECHA (RAC, SEAC gave their opinions on the suggested restriction taking into account comments submitted by the interested parties during the public consultation (see Art 70 and 71).
Information on the measuring devices
Mercury is used in certain thermometers, where a glass tube is filled with mercury and a standard temperature scale is marked on the tube. With changes in temperature, the mercury expands and contracts in a consistent manner and the temperature can be read from the scale. A mercury thermometer can be easily identified by the presence of a silver bulb. If the bulb is red, blue, purple, green or any other color, then it is not a mercury thermometer.
Mercury thermometers can be used to determine body temperature (fever thermometers), liquid temperature, and vapor temperature. Mercury thermometers are used to measure the temperature of liquids and vapors in households, laboratory experiments at educational and medical institutions, and industrial applications. Common household uses of mercury thermometers include fever thermometers and oven, candy and meat thermometers.
Mercury fever thermometers are made of glass the size of a straw, with a silvery-white liquid inside, and are a common item in many households, schools and medical facilities. There are two general types of mercury thermometers that measure body temperature:
- oral/rectal/baby thermometers, containing about 0.61 grams of mercury; and
- basal temperature thermometers, containing about 2.25 grams of mercury.
Alternative Mercury-free Fever Thermometers that are reliable and accurate, are available in the market today. Alternatives that are most comparable in cost and use to the mercury fever thermometer include battery and solar powered digital thermometers. These can all be used orally, rectally, or in the armpit.
When choosing a battery powered digital thermometer, it is advisable to select one that contains a replaceable battery. The battery is a button cell battery and may contain a small amount of mercury, so it should be recycled through a local battery collection program or the existing household hazardous waste collection center.
Within the educational and medical sectors, mercury thermometers may be used in many applications, including chemical experiments, water and acid baths, blood banks, ovens and incubators
Industrial uses of mercury include: use in power plants and piping, chemical tanks and vats, heating and cooling equipment, breweries, canneries, bakeries, candy making, dairies, ships, wineries and distilleries, and paint kettles.
Thermometer cleanup and disposal: When a thermometer breaks during usage or if it is not properly disposed of, it will release mercury vapors that are harmful to human and ecological health. The US EPA website has information on what to do when a thermometer breaks or spills.
Many states and local agencies have developed collection/exchange programs for mercury-containing devices such as thermometers. Some counties and cities also have household hazardous waste collection programs.
Blood pressure gauges (Shpygmomanometers)
A sphygmomanometer or blood pressure meter is a device used to measure blood pressure, comprising an inflatable cuff to restrict blood flow, and a mercury or mechanical manometer to measure the pressure. It is always used in conjunction with a means to determine at what pressure blood flow is just starting, and at what pressure it is unimpeded. Manual sphygmomanometers are used in conjunction with a stethoscope.
The mercury sphygmomanometer has long been considered the “gold standard” of blood pressure measurements because all medical personnel have been trained to use it, the blood pressure readings are fairly reliable, it is often (mistakenly) believed that the device never needs to be calibrated, and it can be used universally – including in special clinical conditions such as arrhythmia, pre-eclampsia and certain vascular diseases where
electronic sphygmomanometers may be less reliable. While mercury-free semi-automated and automated (electronic) sphygmomanometers that measure blood pressure without a stethoscope are, in recent years, more commonly used than mercury devices, they have some limitations.
“Manual” mercury-free sphygmomanometers – used together with a stethoscope – are direct substitutes for mercury sphygmomanometers. Such substitutes include the aneroid sphygmomanometer, which typically uses a pressure dial instead of a mercury manometer; the digital sphygmomanometer, which shows blood pressure readings on a digital display; and the newer hybrid sphygmomanometer, which shows blood pressure
readings on a non-mercury (e.g. liquid crystal display) column.
In past years, most manual mercury-free sphygmomanometers were subject to a range of problems such as unreliability, fragility, need for more frequent calibration, etc., that gave them a reputation for substandard performance. Even now, the reliability and performance of a sphygmomanometer depends to a large extent on the design and manufacture, although it may also be strongly influenced by the frequency of
maintenance and calibration, the training and experience of the user, the manner in which it is used, etc.
While a number of manual mercury-free sphygmomanometers now on the market have been independently tested (“validated”) and determined to be fully substitutable for mercury sphygmomanometers, some are more expensive to purchase and may have a shorter lifetime than a mercury sphygmomanometer. Combined with the reticence of some health care professionals to trust mercury-free instruments, some hospitals and especially general practitioners in some countries have been reluctant to adopt them.Mercury may be released from manometers and valves during use, as it is often necessary to top up the mercury. Furthermore, end of life sphygmomanometers (and other mercury containing devices) would need to be discarded carefully - as hazardous waste. Especially at health care facilities, hazardous waste management is a critical task not only because of the diversity and quantities of waste handled, but also because substandard practices have the potential to harm the reputation of the entire facility. The failure of a number of health care facilities to treat mercury (and probably other hazardous wastes) properly, may have as a result mercury wastes ending in waste incinerators, or landfills causing emissions to air, water and soil, increasing the risks to human health and the environment.
A barometer is a scientific instrument used in meteorology to measure atmospheric pressure. It can measure the pressure exerted by the atmosphere by using water, air, or mercury. Pressure tendency can forecast short term changes in the weather. Numerous measurements of air pressure are used within surface weather analysis to help find surface troughs, high pressure systems, and frontal boundaries. Barometers use large quantities of mercury (around 999 g more than a fever thermometer). Any barometer breakage poses an enormous risk of contamination and severe health effects, not to mention significant clean up costs. Mercury free barometers, both aneroid and digital, are already available in the market, and can be transported without the need for hazardous packaging. Breakage of mercury barometers does not only happen in the manufacturers’ workshop, but can and do occur in schools, homes, and other buildings. These breakages can involve significant clean up costs (evacuation & closure of schools, hazardous waste clean up & disposal measures), risk of contamination into the environment through improper disposal, and risk of health effects (e.g. through direct inhalation)
Porosimetry is a major mercury user.The purpose of porosimeters is the measure of the porosity of a sample – that could be sintered filters, catalytic converters, fuel cells, bone replacement materials, ceramics, etc. The advantage of mercury is that it is a fast, reliable technique covering a wide range of pores from 0.003 ìm to 400 ìm. There are various alternatives, but none is ideal for certain substances and/or certain pore sizes. Further, as in the case of sphygmomanometers, there are certain validation standards that would also have to be revised in order to move away from mercury porosimetry. After testing, about 4% of mercury remains in a typical sample, the rest is recovered for re-use by the company that is doing the testing. That means that over a period of time, testing 25 samples, you use 100% of your quantity of mercury in the machine. The question is what happens to the mercury that remains in the samples. Industry assures us that it is possible to recycle 100%. Due to the fact that this process is normally done in research labs, one would hope that a high rate of recycling is carried out – but there is no information to confirm that. For the research that was done for the 2008 COWI/Concorde study for DG Environment, there was an estimation of 25-30% of recycling in addition to a certain amount of mercury in samples that goes to final disposal – for example in salt mines in Germany. However, there is little real data to back up these numbers.
Even though several measures have been taken to control the use and emissions of mercury in the EU, some uses of mercury still remain, such as its use in the following measuring devices used by industry and professionals: Barometers, manometers, sphygmomanometers and strain gauges used to measure pressure, and thermometers to measure temperature. Porosimeters, pycnometers and metering devices for determination of the softening point measure different parameters related to the structure and porosity of a sample. Mercury electrodes used with specific devices like polarographs, for instance to determine trace elements in the environment and in biological fluids.
Barometers, manometers, sphygmomanometers, strain gauges and thermometers contain mercury as an integral part of the device whereas metering devices for determination of the softening point, polarographs (using mercury electrodes), porosimeters and pycnometers use mercury during the measurement and need to be refilled regularly.
Mercury-free alternatives are already available and dominate the market for most of the measuring devices. The alternatives are often electronic devices or devices making use of other liquids such as alcohols for their functioning. For porosimeters and mercury electrodes used in voltammetry no technically feasible alternatives have been identified which would cover all application areas.
Mercury electrodes (polarography)
Polarography is an electrochemical analytical technique which is used in chemical labs, in universities, in industry. Mercury is used as a sensor electrode. Voltage is applied, and currents are measured to this sensor. It is mainly used to determine toxic traces and low concentrations of heavy metals such as lead, cadmium, chromium or mercury.The center of the whole device is a glass vessel and three electrodes immersing in this glass vessel, including the mercury sensor. The mercury electrode is a glass capillary, from which a small mercury drop is extruded. In the glass vessel the sample we want to analyze is introduced. At the end of the determination the mercury drop falls off to the bottom of the vessel and from there it can be collected at the end of the measurement. Filling of the electrode is typically 6 milliliters which is approximately 80g mercury. Under normal circumstances this will last for half a year to one year of every day use. Based on the consumption of mercury and estimated number of polarographs worldwide we assume that the total consumption is about 250 to 350kg worldwide. From a (mercury) life cycle perspective of the user, usually, the mercury is purchased from a supplier, it is used in a lab, collected in a close container and finally returned to a recycler.
Alternatives: the technique is used for the determination of heavy metals. There are other techniques existing that have a similar application. They are either non-electric techniques – for example optical/spectroscopic techniques – or other sensors (with reduced mercury content or completely mercury-free sensors) using similar principals of measurement as polarography. There are spectroscopic techniques that are very well established, which are usually the standard techniques in most of the labs worldwide. They are good for the majority of application. However,there are some limitations:
- Only total element concentration detection.
·High investments (purchase, running)
·Problems with some sample matrices (e.g. sea water, pure chemicals)
·Laboratory infrastructure required
Besides liquid mercury as a sensor there are other sensors existing, some of them are commercially available and some others are still in a research state. Typically they are based on carbon or on noble metals like gold or platinum. These sensors have quite severe restrictions – this is why most of them are only used in research fields and not in routine. If we look into industry we have nearly no users using such sensors because of the restrictions. Their advantages are that they can replace some mercury applications and they are sometimes even more sensitive than the mercury sensor.