Formaldehyde

50-00-0

Colourless gas.

Characteristic, hay, strawlike, pungent.

USSR: human odour perception; non perception: 0.05 mg/m3;
                                  perception: 0.07 mg/m3;
      human reflex response; no response: 0.07 mg/m3
                       adverse response: 0.084 mg/m3.

Odour index: 5000000 at 20 °C 
(Verschueren 1983).

30.03

Formaldehyde gas adsorbs somewhat to clay mineral at high
concentrations of the gas, which is important to its use as a
soil fumigant (De & Chandra 1978).

Very soluble, up to 55% (Merck Index 1983).

Formaldehyde absorbs UV radiation at wavelengths of 360 nm and
longer, so is capable of photolyzing in sunlight (Hampson
1980).

The measured half-life for photolysis as measured in simulated
sunlight is 6.0 hr (Su et al. 1979).

There are two photolytic channels; one producing H2 and CO and
the H and CHO (Lowe et al. 1981).

Based on its rate of reaction with photochemically produced
hydoxyl radicals, formaldehyde will have a half-life of 19
hours in clean air and about half that long an polluted air
(Howard 1989).

The hydroxy radical initiated oxidation of formaldehyde also
occurs in cloud droplets to form formic acid, component of acid
rain (Chameides & Davis 1983).

When formaldehyde is irridiated in a reactor, the half-life is
50 min and 35 min in the absence and precence of NO2,
respectively. 
The primary products formed are formic acid, HCl
and CO (Howard 1989).

Reaction with nitrate radicals, insignificant during the day,
may be an important removal mechanism at night (USEPA 1982).

Photooxidation half-life in air:
7.13hr - 71.3hr,
based upon measured rate constant for reaction with hydroxyl
radical in water (Howard 1991).

Atmospheric photolysis half-life:
1.25hr - 6hr,
based upon measured photolysis for gas phase formaldehyde
irradiated with simulated sunlight; t1/2 calculated for
sunlight photolysis (Howard 1991).

The hydroxy radical initiated oxidation of formaldehyde also
occurs in cloud droplets to form formic acid, component of acid
rain (Chameides & Davis 1983).

When formaldehyde is irridiated in a reactor, the half-life is
50 min and 35 min in the absence and precence of NO2,
respectively. 
The primary products formed are formic acid, HCl
and CO (Howard 1989).

In water, formaldehyde is hydrated and the hydrate does not
have a chromophore that is capable of adsorbing sunlight and
photolytically decomposing (Chameides & Davis 1983).

Photooxidation half-life in water:
201d - 22yr,
based upon measured rate constant for reacion with hydroxyl
radical in water (Howard 1991).

Aerobic half-life:
1d - 7d, scientific judgement based upon unacclimated aqueous
aerobic biodegradation screening test data (Howard 1991).

Anaerobic half-life:
4d - 28d, scientific judgement based upon unacclimated aqueous
aerobic biodegradation half-life (Howard 1991).

Biodegradation:
  +O2
  ->  HCOOH -> CO2 + H2O
HCHO
  ->  CH3OH -> CO2 + H2O
  +H2

Inhibition of anaerobic sludge digestion; at 100 mg/l; aerobic
degradation; 135 - 175 mg/l (Verschueren 1983).

Solutions containing formaldehyde are unstable, both oxidizing
slowly to form formic acid and polymerizing (Kirk Othmer 1980).

In the precence of air and moisture, polymerization readly
takes place in concentrated solutions at room temperatures to
form paraformaldehyde, a solid mixture of linear
polyoxymethylene glycols cointaining 90-99% formaldehyde (USEPA 
1984).

In dilute aqueous solution formaldehyde exists almost
exclusively as hydrated gem-diol (CH2(OH)2) (Dong & Dasgupta 
1986).

Formaldehyde in aqueous effluent is degraded by activated
sludge and sewage in 48 - 72 hr (Howard 1989).

In a die-away test using water from a stagnant lake ,
degradation was complete in 30 hr under aerobic conditions and
48 hr under anaerobic conditions (Kitchens et al. 1976).

Experiments performed on a variety of fish and shrimp show no
bioconcentration of formaldehyde (Hose & Lightner 1980) (Sills 
& Allen 1979).

Skin and eye irritation data:
skin, human, 0.150 mg, mild;
eye, human, 1 ppm, 6 min nse, mild;
skin, rabbit, 540 mg open, mild;
eye, rabbit, 0.050 mg, 24 hr, severe;
eye, rabbit, 10 mg, severe 
(Sweet 1987).

Man: severe toxic effects: 100 ppm = 120 mg/m3, 1min;
symptoms of illness; 30 ppm = 36 mg/m3;
unsatisfactory: 10 ppm = 12 mg/m3.
conc. ppm    exposure time       effects
2-3                              tingling of eyes, nose and
                                 throat;
4-5          10-30 min           irritation; discomfort;
                                 lacrimation; some tolerance 
                                 develops; tolerable for
                                 some,not all;
20           short               discomfort and lacrimation;
12                               severe irritation;
13.8         30 min              nasal and eye irritation
                                 and lacrimation;
4            5 min               severe eye irritation;
1            5 min               8 % of test panel reported
                                 eye irritation;
2            12 min              24 % of test panel reported
                                 eye irritation;
4            5 min               100 % -"-
2-4          5 min               33 %  -"-
0.9-1.6 %    occup.              intense irritation;
             exposure            itching of eyes;
                                 dry and sore throat;
                                 increased thirst;
                                 disturbed sleep
(Verschueren 1983).

Eye irritation threshold: 3 - 10 ppm (Verschueren 1983).

Mutation data:
cyt, hmn, lym, 10 mg/l;
dnd, hmn, lug, 0.1 mmol/l;
DNA inhibition, esc, 5 mmol/l;
dnr, esc, 1.95 mg/l;
dns, hmn, hla, 10 nmol/l;
dlt, dmg, orl, 1300 ppm;
mrc, smc, 24 mmol/l;
microbial mutation without S9, microorganisms, 10 ppm;
mma, mus, lym, 25 mg/l;
otr, ham, kidney, 4 mg/l;
sin, dmg, orl, 250 ppm;
sce, ham, ovr, 0.110 mg/l;
sperm morphology, rat, orl, 200 mg/kg
(Sweet 1987).

305 kg formaldehyde (37 %)/ha when applied to soil depressed
growth of mycorrhizal sour orange (Citrus aurantium) seedlings
(Nemec 1980).

Bacteria: Escherichia coli, toxic, 1 mg/l (Verschueren 1983).

Toxicity threshold (cell multiplication inhibition test):
(formalin 35% w/w) bacteria (Pseudomonas putida): 14 mg/l
(Bringmann & Kühn 1980a).

Removal/secondary treatment: 57% - 99%,
removal percentages based upon data from a semicontinuous
sewage (low t1/2) and continuous activated sludge (high t1/2)
biological treatment simulator (low t1/2) (Howard 1991).

Ctenopharyngodon idella: LC50, 0.13 d, 160 ml/l;
Cyprinus carpio: LC50, 0.13 d, 197 ml/l
(Rosicky et al. 1986).

Toxicity threshold (cell multiplication inhibition test) 
(35 % w/w): bacteria (Pseudomonas putida): 14 mg/l
algae (Microcystis aeruginosa): 0.39 mg/l
green algae (Scenedesmus quadricauda): 2.5 mg/l
protozoa (Entosiphon sulcatum): 22 mg/l
protozoa (Uronema parduczi Chatton-Lwoff): 6.5 mg/l
(Verschueren 1983).

Scenedesmus, toxic, 0.3 - 0.5 mg/l;
Daphnia toxic, 2 mg/l (Verschueren 1983).

Toxicity threshold (cell multiplication inhibition test):
(formalin 35% w/w)
green algae (Scenedesmus quadricauda): 2.5 mg/l
protozoa (Entosiphon sulcatum): 22 mg/l
(Bringmann & Kühn 1980a).

Reduction of amenities:
taste and odour caused at 50 mg/l;
osour threshold: average; 49.9 mg/l; range: 0.8 - 102 mg/l
(Verschueren 1983).