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close this bookAsbestos Overview and Handling Recommendations (GTZ, 1996)
close this folderPart II. Asbestos
close this folder3. Environmental aspects and health hazards due to Asbestos
View the document3.1 Introduction
View the document3.2 Asbestosis
View the document3.3 Mesothelioma
View the document3.4 Other health hazards
View the document3.5 Risk determination

3.5 Risk determination

There is no way to directly measure the health risks, in particular the cancer risk, caused by Asbestos fiber concentrations in the environment. A risk quantification is only statistically possible through evaluation of sickness data or mortality numbers of persons occupationally subjected to Asbestos. Based on relationship known for over 50 years, there have been longterm investigations on this question, in Germany particularly through the Employers Associations for Accident Insurance (Berufsgenossenschaflen). Usually, however, direct measurement of Asbestos concentrations at the workplace is no longer possible, since due to the relatively long latent period, the past working conditions can only be approximately reconstrued. Through such experiments, the Asbestos fiber concentrations can only be estimated, and particular experimental conversion factors are scientifically applied. Additionally, a number of other factors play a significant role in this relationship, as described.

The investigations indicate that the Asbestos concentrations in the workplace in the '30s and '40s were a factor of 3-4 higher than the typically found Asbestos concentrations today, which originate primarily from old Asbestos contaminations. The emission from Asbestos processing has been greatly reduced, due to the strict legal regulations and the resulting limitations or prohibitions in use.

Table 10 presents the results of measurements of the ambient concentration of critical Asbestos fibers (> 5 ym in length, < 3 ym in diameter and ratio of length to diameter > 3:1 ) in Germany during 1984 and 1989. Table 11 provides further results of outdoor air measurements of Asbestos.

Table 10: Asbestos Fiber Concentrations

Concentration (F/m³)


50 - 140

in the area of use of Asbestos cement corrugated sheets

50 - 150

in urban areas, including those noted with elevated traffic density

80 - 350

in the area of factories processing Asbestos fibers

Source: Central Employers Association for Accident Insurance (Hauptverband der Gewerblichen Berufsgenossenschaflen), St. Augustin, Germany

The range of Asbestos fiber concentrations resulting from various activities is evident in Table 10. Asbestos cement products which were used outdoors, typically as roofing or as facade sheets, are considered to be relatively low health risks, as are indoor wall and ceiling coverings made of Asbestos, given the following limiting conditions: no mechanical processing occurs; the Asbestos is firmly bound in a cement matrix; and the binding in the matrix has not been impaired by age or mechanical wear. For outdoor air, Asbestos cement sheets on roofs and facades currently represent the most important emission source in Germany. This can vary from country to country, however. For instance, products of friction (especially Asbestos containing brake linings) in urban areas with elevated traffic in countries which have not prohibited such brakes, can lead to high fiber releases. This is apparent from the Table 11.

Table 11: Asbestos Fiber Concentrations

Fiber Concentration (F/m³)

Areas

< 100

rural areas

100 - 200

urban areas

100 - > 300

immediate vicinity of Asbestos emitters

to > 20 Million

exhaust from Asbestos containing car breaks with compressed air or from abrasive cutting of Asbestos containing materials

to > 500 000

roofing as well as drilling work on Asbestos cement

occasionally > 20.000

indoor air: in areas of sprayed Asbestos (depending on the condition of the material's surface)

Source: UBA-Report 5/91 - changed

The health risk due to Asbestos fiber concentrations can only be quantified on the basis of case numbers. As shown in Table 12, nearly 70% of the compensated occupational illnesses in Germany between 1978 and 1986 were caused by Asbestos. Therefore, Asbestos is the primary carcinogen in the workplace. It should be noted that due to the long latent period, an increase in the reported occupational illnesses caused by Asbestos may be expected in the future. This holds for both Asbestos-caused lung and larynx cancer as well as for mesothelioma.

Table 12: Occupational Illnesses for which Compensation has been Paid in the Federal Republic of Germany during the Period of 1978 - 1986

Cause

Number of Cases


no.

%

Asbestos

1,021

68. 5

aromatic amines

149

10.0

quartz

66

4.4

pitch, tar, tar oil

54

3.6

benzine

38

2.5

chromates

38

2 5

uranium. decay products

28

1.9

oak and beach wood dust

22

1.5

halogenated hydrocarbons

20

1.3

arsenic and compounds

16

1.1

halogenated ether

12

0.8

others

29

1.8

Total

1,491

100

Source: Central Employers Association for Accident Insurance (Hauptverband der Gewerblichen Berufsgenossenschaften), St. Augustin, Germany

Table 13: Mortality Risk of Various Activities and Occurances


Individual Risik per Year

Average Risk per 1,000 Persons/Year

automobile accidents

2.2 E - 04

0.22

fire and explosions

3.7 E - 05

0.037

30 mrem radiation exposure

1.5 E - 05

0.015

accidents in the home

1.2 E - 05

0.012

therapeutical, medical or surgical treatment

6.3 E - 06

0.0063

electrical shock

5.0 E - 06

0.005

1000 Asbestos fibers/m³ (Mesotheliom)

1.2 E - 06

0.0012

struck by lightning

4.4 E - 07

0.00044

bites and stings (from poisoness animals)

1.2 E - 07

0.00012

Source: Umweltbundesamt (Publ): Asbestos - Construction Material, Health Risks, Report 5/91 of the UBA, Berlin 1991

Table 13 compares the mortality risk associated with mesothelioma caused by Asbestos fiber inhalation with other risk factors.

In general, the risk of becoming ill from Asbestos depends on the following factors:

· age during exposure,
· length of exposure,
· fiber concentration,
· type of Asbestos.

It is not possible to define limits below which health risks can be entirely excluded. For this reason, the goal is always to achieve a minimal Asbestos fiber exposure. New research in the U.S.A. particularly emphasizes the health hazards from amphibole Asbestos and pleads for a general prohibition of this type of Asbestos.

In summary, the following has been determined:

· The health risk from the inhalation of Asbestos fibers which can reach the lungs is
generally considered critical and is undisputed worldwide, with few exceptions. The
actual health hazard depends on further factors (type of Asbestos, exposure length, fiber
concentration, age during exposure, other stimuli (e.g. smoking), etc.).

· The health risk of oral intake of Asbestos fibers from Asbestos contaminated drinking
water has not been as well researched and is currently the focus of further studies. Past
investigations have reached different interpretations.

· According to the current research findings, a release of Asbestos fibers from liquid
media (drinking water, beverages) into the surrounding air is only regarded as potentially
critical to the health for extremely high fiber concentrations in the liquid (>> I million
fibers/liter).

· For industrial uses of water with high Asbestos fiber concentrations, particularly in
industrial cleaning processes, there is a danger of high Asbestos concentrations in the
outdoor air. This area has not been researched very much.