Mass flow analysis of glycol ethers
Summary and conclusions
| Consumption |
| Release to the environment |
| Glycol ether balance |
| Exposure of
and effects on humans and the environment |
A detailed analysis has been made of the consumption in Denmark of glycol ethers in relation to their fields of application, the total amount consumed (in 2000) and the exposure of man and the environment. The analysis is based on information from Statistics Denmark (various annual volumes) and from the Danish Product Register, studies from industries producing pesticides and cleaning agents and from the printing industry and on relevant literature.
Consumption
In 2000, the total consumption in Denmark of glycol ethers was assessed to be approx. 14.800-15.400 tons/year. The consumption of ethylene glycol-based glycol ethers only constitutes 7% of the total consumption and the major part of the consumption is made up of glycol ethers based on propylene glycol (49%) and di- and triethylene glycols (22% and 12%, respectively).
In Denmark, the quantitatively most essential fields of application of glycol ethers are:
 | Production and use of paints, lacquers, inks and sealing compounds (7,000-7,200 tons
corresponding to 47% of the total consumption of glycol ethers) including
| ||||||
| Production and use of cleaning agents (approx. 5,400-5,700 tons corresponding to 36% of the total consumption of glycol ethers) |
In Denmark, glycol ethers are in focus, and the trend is clearly towards substituting less harmful glycol ethers for problematic glycol ethers. The trend is towards a very drastically declining consumption of the small ethylene glycol ethers and the consumption will most probably be close to nothing in the near future. One of the producers of cleaning agents follows the strategy to have glycol ethers removed from their products.
Release to the environment
The emissions to the environment are estimated a.o. by use of partition factors and guidelines stated in the Technical Guidance Document (European Commission 1996).
Table 1 shows the estimated emissions to the air, the water, the waste (incinerated) and to the soil.
According to the estimates, the emission of glycol ethers to the air constitutes approx. 75%, to surface waters approx. 15%, to waste approx. 8% and to the soil approx. 1% of the total emission to the environment. The major part of the glycol ethers in the waste is expected to be degraded/destroyed in the waste incineration plants.
Table 1
Overview of emissions to the air, the water, waste and the soil for 2000.
(tons/year).
Compartment |
Air |
Water |
Waste |
Soil |
Total |
5,300-7,100 |
1,100-1,400 |
600-800 |
100 |
Glycol ether balance
On the basis of the incomplete information on consumption and the releases to the environment estimated on this basis, a rough glycol ether balance was made. The glycol ether balance is thus subject to great uncertainty but it may be used as an indication of the mass flows of glycol ethers. The accumulation is calculated as the sum of imports and production with a deduction of the sold, incinerated and deposited amounts and the emission to the environment.
Figure 1
Mass balance for glycol ethers in Denmark. The stated amounts refer to the
estimated max. concentrations in ktons/year, based on 2000 Figures.
Exposure of and effects on humans and the environment
In general, glycol ethers are biodegradable in the aquatic environment and may thus be transformed in the environment. Glycol ethers are moderately toxic to aquatic organisms, some with EC50 values considerably above 100 mg/L and others with EC50 values below 100 mg/L. Glycol ethers are not expected to bioaccumulate in the aquatic environment.
Glycol ethers are expected to leach easily from soil column and may thus leach to the ground water.
The amounts of glycol ethers used in Denmark today are not assumed to constitute any immediate risk of effects on the aquatic organisms. An increased consumption within the offshore industry may, however, give rise to effects in the environment. New offshore products are currently being developed and their use may lead to larger emissions to the North Sea.
Some ethylene glycol-based glycol ethers have been shown to be both reproduction toxic and genotoxic and many glycol ethers are moderately irritating to the eyes.
For a preliminary assessment of which combinations of glycol ethers, consumption and application areas that constitute the highest risks to humans, a combined exposure and screening model was used for a health rating of chemical substances. The model was developed by the Danish Toxicology Centre (DTC). In general the human exposure in the production industry was assumed to be limited by use of protective equipment (e.g. gloves, safety glasses, exhaust ventilation).
By use of this combination model, it was assessed that the use of glycol ethers in the areas of: construction industry (paints, flooring), metal industry (lacquering, painting, polishing), wood industry and the use of glycol ethers in cleaning lead to the highest human exposure. Furthermore, measurements of the concentrations in the work environment have shown that some working operations give rise to high exposure concentrations in the air, e.g. cleaning of various production equipment (printing industry, metal industry) and printing (screen printing, silk screen printing, gravure and offset printing).
For selected glycol ethers, an estimate was made of the concentration of glycol ethers in the air when no applicable measurement data were available.
Apparently, the use of the examined glycol ethers in cleaning agents and wall paints is not causing concentrations in the air that exceed the limit values of the glycol ethers in question.
In various metal-working industries, the highest exposure concentrations of propylene glycol monomethyl ethers (PGME), propylene glycol monoethyl ether-acetate (PGMEA) and ethoxy ethyl-acetate (EGEA) were found in the clearing process of ships and boats, cleaning and painting. No exposure concentrations of PGMEA and PGME were found that exceeded the limit values of the substances whereas measured concentrations of EGEA exceeding its limit value (cleaning operation) occurred.
In garages, the highest measured exposure concentrations of PGME and PGMEA were found in the cleaning process after spray painting, repair, painting, mixing/cleaning/etc. No exposure concentrations of PGMEA and PGME were found that exceeded the limit values of the substances.
When used in the wood industry, the highest exposure concentrations of glycol ethers were found in the processes of "feeding the machine", staining and spray painting. The observed concentrations within the wood industry did not exceed the limit values of the two substances.
Furthermore, it should be noted that various working operations in connection with printing and production of inks and sealing compounds may result in increased exposure concentrations in the air exceeding the limit values of the substances.
It should also be mentioned that, in the risk assessments of DEGBE and DEGME (European Commission 2000a and 2000b), it was among other things found that effects from exposures via inhalation of and skin contact with DEGBE in the working environment with spray painting cannot be precluded. For DEGME, it was found that the exposure to DEGME via skin contact in the working environment with production of DEGME, production of products containing DEGME and manual use of products containing DEGME should be limited/minimized.
The effects of dermal exposure to the investigated substances were not assessed for the substances. Easily accessible effect data on skin exposure to PGME and PGMEA were sought but not found. When using paints containing the most commonly used glycol ethers, the estimated dermal exposures to the glycol ethers were at the exposure level of DEGME, at which it cannot be precluded that effects may occur, but below the exposure level of DEGBE, at which it cannot be precluded that dermal exposure may result in effects. When using cleaning agents containing the most commonly used glycol ethers, the estimated dermal exposures to the glycol ethers were at the exposure level of DEGME, at which it cannot be precluded that effects may occur, at the exposure level of DEGBE, at which irritation effects may occur but below the exposure level, at which it cannot be precluded that repeated dermal exposures to DEGBE may result in systemic effects.