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DESIGNATIONS
CAS No.: 10028-15-6
Registry name: Ozone
Chemical name: Ozone
Synonyms, Trade names: Trioxygen
Chemical name (German): Ozon
Chemical name (French): Ozone
Appearance: colourless gas or dark blue liquid (at -112°C)
BASIC CHEMICAL AND PHYSICAL DATA
| Empirical formula: | O3 |
| Rel. molecular mass: | 48.0 g |
| Density: | 2.15 g/l (gaseous) at 0°C and 1013 hPa, 1.571 g/cm3 at -183°C (liquid) |
| Relative gas density: | 1.66 |
| Boiling point: | -112°C |
| Melting point: | -192.7°C |
| Vapour pressure: | 7 x 106 Pa at -20°C |
| Flash point: | |
| Ignition temperature: | |
| Explosion limits: | |
| Odour threshold: | 0.01-0.02 ppm |
| Solvolysis/solubility: | in water 490 ml/l at 25°C; highly soluble in Freon 12 |
| Conversion factors: | 1 mg/m3 = 0.51 ppm |
| 1 ppm = 1.995 mg/m3 |
ORIGIN AND USE
Usage:
Used in laboratories for ozonisation; in industry for bleaching
oils, greases, waxes, synthetic fibres, papers, cellulose and
textiles; as disinfectant in breweries, cold stores and the like;
for artificial ageing of brandy and disinfection of drinking
water. It is also used for sterilising swimming-pool water and
for the deodourisation of unpleasant smells. Further applications
result from the sterilising effect of ozone in the manufacture,
preservation and storage of foodstuffs.
Origin/derivation:
Ozone is produced from atmospheric oxygen in the presence of UV
light at extremely high temperatures and e.g. in an electrical
corona discharge. Its formation under natural conditions
presupposes the existence of appropriate precursors (in
particular N-oxides and hydrocarbons) which are converted to
ozone in the presence of sufficient sunlight. The main sources of
workplace impact are inert-gas welding, photocopiers, air
filtration systems, UV sterilisation systems and UV lamps where
ozone is produced in the respiratory zone from molecular oxygen
through UV irradiation. The only economical method of producing
ozone is that of electrical corona discharge.
Toxicity
| Humans: | LD 15-20 ppm | acc. ULLMANN, 1978 |
| 0.001 mg/l air (definite irritation) | acc. TAB. Chemie, 1980 | |
| 0.002 mg/l air (1.5 h; damage) | acc. TAB. Chemie, 1980 | |
| Mammals: | ||
| Guinea pigs | LC50 51.7 ppm | acc. ULLMANN, 1978 |
| Mouse | LC50 21 ppm | acc. ULLMANN, 1978 |
Note:
Young animals react more sensitively to the inhalation of
ozone than older ones. Physical exercise increases the toxicity
level due to increased ventilation or stress.
Characteristic effects:
Humans/mammals: Ozone is extremely irritating to the mucous membranes of the eyes, nose and throat. The main damage is however caused in the respiratory tract and this manifests itself in a reduced respiratory volume or even in bronchitis and pulmonary oedemas. Chronic exposure may lead to chest pain, headache and dizziness even if the ozone concentration is low. The toxicity of ozone is attributed in part to the oxidative decomposition of unsaturated fatty acids in the organism.
Plants: The direct effect of ozone is the destruction of chlorophyll and in particular chlorophyll b. The extent to which ozone is involved in the phenomenon of "dying forests" has been the subject of discussion for some time. Ozone absorption takes place exclusively via the atmosphere. There is a considerable difference in the sensitivity of various plants. Acute symptoms of ozone damage are necrosis, chlorosis and so-called water marks.
ENVIRONMENTAL BEHAVIOUR
Water:
The rate at which ozone decomposes in an aqueous solution
increases with increasing pH. In the presence of water, ozone
oxidises all metals to the maximum possible extent.
Air:
Atmospheric air pollution caused by ozone originates from the
photochemical formation of smog. The first step in this process
is the photolysis of ozone.
Degradation, decomposition products, half-life:
Gaseous ozone is subject to spontaneous decomposition: O3
(r) O2 + 1/2 O2
+ 284 kJ with a half-life of 3 days (at 20°C), 8 days (at
-15°C), 18 days (at -25°C) or 3 months (at -50°C); the
decomposition process does however only involve simple allotropic
conversion of the same element.
ENVIRONMENTAL STANDARDS
| Medium/acceptor | Sector | Country/organ. | Status | Value | Cat. | Remarks | Source |
| Air: | CH | (L) |
100 µg/m3 |
1) | acc. LAU-BW, 1989 | ||
| CH | (L) |
120 µg/m3 |
2) | acc. LAU-BW, 1989 | |||
| D | G |
120 µg/m3 |
3) | acc. LAU-BW, 1989 | |||
| WHO | G |
150-200 µg/m3 |
4) | acc. LAU-BW, 1989 | |||
| WHO | G |
100-120 µg/m3 |
5) | acc. LAU-BW, 1989 | |||
| WHO | G |
200 µg/m3 |
6) | acc. LAU-BW, 1989 | |||
| WHO | G |
60 µg/m3 |
7) | acc. LAU-BW, 1989 | |||
| WHO | G |
65 µg/m3 |
8) | acc. LAU-BW, 1989 | |||
| Workp | D | L |
0.2 mg/m3 |
MAK | DFG, 1989 | ||
| Workp | DDR | (L) |
0.2 mg/m3 |
acc. Tab. Chemie, 1980 | |||
| Workp | SU | (L) |
0.1 mg/m3 |
acc. KETTNER, 1979 | |||
| Workp | USA | (L) |
0.2 mg/m3 |
TWA | acc. ACGIH, 1986 | ||
| Workp | USA | (L) |
0.6 mg/m3 |
STEL | acc. ACGIH, 1986 |
Notes:
1) Exposure time: 98% of annual half-hour average
2) Exposure time: 1 hour average; may be exceeded once
3) Exposure time: half-hour average; protection of humans
4) Exposure time: 1 h; protection of humans
5) Exposure time: 8 h; protection of humans
6) Exposure time: 1 h; protection of vegetation
7) Exposure time: mean value over entire vegetation period
8) Exposure time: 24 h; protection of vegetation
Assessment/comments
Any assessment of ozone must give consideration to two different aspects. Ozone which pollutes the air just above the ground harms the respiratory organs and plants and thus should be avoided as far as possible. In view of the secondary formation of ozone, this means reducing above all the nitrous emission levels.
At the same time, chlorinated fluorocarbons and nitrous oxides must not be allowed to reach the upper strata of the atmosphere (ozonosphere at an altitude of 50 - 60 km), since such substances deplete the vitally important ozone layer which absorbs dangerous UV radiation. While ozone concentrations close to the ground have a harmful effect, their presence in the upper atmosphere is absolutely vital.