Environmental Project, 1102 – Alternatives to mercury-containing measuring devices

Alternatives to mercury-containing measuring devices

Summary and conclusions

The investigation shows that mercury-containing manometers, barometers and thermometers, apart from certain applications in laboratories, have been totally phased out in Denmark and satisfactory, cost-efficient alternatives are available for all identified applications. For blood pressure measurements, mercury-containing sphygmomanometers are still requested by some general medical practitioners and a few hospital departments. In recent years the electronic and mechanical mercury-free devices have been improved, and devices which are validated with reference to internationally recognised protocols, are marketed at prices corresponding to the price of mercury-containing blood measurement devices. The disadvantage of electronic devices is that they for the user are a kind of "black box", and it is not easily recognisable whether they function correctly, which means that they must be checked more regularly. In spite of this, the electronic devices, which also have significant advantages, supersede mercury-containing devices for most applications concurrently with a significant improvement of the electronic devices and a drop in the price. Electronic equipment has also replaced mercury-containing devices for advanced measurements and calibration of other thermometers, manometers and barometers.

Historic consumption of mercury with measuring devices
The consumption of mercury for measuring devices in Denmark has during the period from 1982/83 to 2000/01 decreased by a factor of 100 (see table 1). The driving forces behind the decrease have partly been the development of new technologies, in particular the development of electronic devices for automatic measurements, partly been environmental concern which has also resulted in a ban of the marketing of some of the mercury-containing measuring devices.

Table 1 Mercury consumption in relation to measuring devices in Denmark

Application area	Mercury consumption (kg Hg/year)
	1982/83	1992/93	2000/01
Fever thermometers	750	50	1.1
Other thermometers	1,300 - 1,800	100	15 - 20
Other measuring and control devices including blood measurement devices and mercury for maintenance of existing devices	430 - 630	500	10 - 50
Total	2,480 - 3,180	650	26.1 - 71.1

Thermometers other than fever thermometers
The marketing of mercury-containing thermometers other than fever thermometers is today banned in Denmark except for marketing of thermometers for calibration of other thermometers and for use in laboratories.

Alternatives for all original applications of mercury-containing thermometers are available on the market (see table 2). The price of alternatives varies significantly. Liquid-in-glass thermometers are available at the same price as mercury thermometers, whereas the price of some electronic thermometers is up to ten times the price of mercury thermometers. Electronic thermometers are widely used for all applications, because the advantages of the automatic measurements and datalogging compensate for the higher price.

Table 2 Marketed alternatives for mercury-containing thermometers in Denmark

Application area / product type	Marketed alternatives	Price of alternatives compared to mercury thermometers	Comment
Mercury-in-glass thermometers for machines, engines, boilers, etc.	Liquid-in-glass thermometer (up to 250°C)	~ same price
	Dial thermometers (up to 650°C)	~ 2-4 times more
	Electronic thermometers	up to 10 times more	Widely used for automatic measurements and datalogging
Mercury-in-glass thermometers for ambient air temperature measurements incl. min/max measurements	Liquid-in-glass thermometer	~ same price
	Electronic thermometers	up to 10 times more	Used for automatic measurements, datalogging and standard equipment of weather stations
Mercury dial thermometers for remote control in the industry and on ships	Dial thermometers with capillaries with other liquid or gases	~ 2-4 times more
	Electronic thermometers	up to 10 times more	Widely used for automatic measurements and datalogging
Mercury-in-glass glass thermometers for laboratory use	Liquid-in-glass thermometer (at 1 degree)	~ same price as ordinary Hg thermometer
Mercury-in-glass glass thermometers for laboratory use	Electronic thermometers (at 0.1 degree resolution at a wide temperature range)	Up to 10 times more than ordinary Hg thermometers ~ same price as certified Hg thermometers	Widely used for automatic measurements and datalogging

The liquid-in-glass thermometers can substitute for mercury-in-glass thermometers for most applications except for measurements in the temperature range above 250°C and for measurements in laboratories at less than 1 centigrade resolution. For high-temperature applications in the industry, the mercury thermometers are typically replaced by dial thermometers for manual reading or by electronic thermometers. For high-resolution measurements the mercury thermometers are to some extent replaced by electronic thermometers, but the mercury thermometers are still widely used in laboratories, e.g. for temperature measurements in synthesis baths.

A barrier for phasing out mercury thermometers in laboratories is that the use of mercury thermometers is prescribed by some standards used in the laboratories. Development of revised standards would encourage mercury substitution in the laboratory sector.

Barometers
Electronic barometers for automatic measurements of barometric pressure have in Denmark totally replaced mercury barometers for professional use in weather stations, airports, etc. Electronic barometers are also used for calibration of other barometers. The electronic barometers are as precise as the mercury barometers and have the advantage of automatic data logging. As mercury barometers have not been marketed in Denmark for many years, a price comparison has not been possible, but a study from the USA concludes that aneroid (mechanical liquid free) and electronic barometers are cost effective alternatives. Even though the electronic barometers may be more expensive than mercury thermometers, the lower price of mercury barometers would most probably not be a decisive property for the main part of the professional users. If available at significantly lower prices, the mercury barometers could perhaps be reintroduced for a few applications, where automatic reading is not requested.

Blood pressure measuring devices
The use of mercury sphygmomanometers for blood pressure measurements are not prohibited in Denmark. Mercury sphygmomanometers are still requested by some general medical practitioners and to a small extent by some hospital departments.

For use by the general public for measurements in the home, semi-automatic electronic devices has totally replaced mercury sphygmomanometers.

In hospitals, mercury sphygmomanometers have nearly 100% been replaced by aneroid (liquid-free) manual sphygmomanometers or electronic semi-automatic and automatic devices. The difference between the application patters in hospitals and by the general medical practitioners is partly that in hospitals use more advanced and expensive electronic equipment, partly that the hospitals have technical departments responsible for the maintenance of the equipment.

Mercury-free devices, validated with reference to the protocols of the British Hypertension Society or the International Society of Hypertension are available at approximately the same price as mercury sphygmomanometers.

The use of mercury-containing strain gauges, and alternatives to these devices, has not been investigated; reference is made to a recent Swedish study.

Other measuring devices
Mercury has previously, and to a small extent, been used in other types of measuring devices. The marketing of such devices in Denmark has been banned for some years. The alternatives marketed today have not been investigated in this project.

There are no current exemptions to the Danish ban.