Acrylaldehyde

Endpoint summary

Additional information

Stability

The stability of acrolein in the atmosphere is limited by the rapid gas-phase reactions with the hydroxyl radical and ozone. The calculated half-life of acrolein for the reaction with the OH-radical in the troposphere (*OH concentration 5 x 10⁵molecules/cm³, 24 hours) is less than one day and is in accordance with the half-life values derived from experiments. Unlike to the US ATSDR Report and the EU RAR the WHO Report stated the calculated atmospheric half-life of acrolein, based on rate constants for hydroxyl radical reaction, to be between 3.4 and 33.7 h. Other degradation routes, such as the reaction with nitrate radical (night-time; half-life: 16 days) and ozone (half-life: 59 days) as well as photolysis (daytime; half-life: 10 days in the lower troposphere and less than 5 days in the upper troposphere), are considered to be less significant. Based on the short estimated half-lives, acrolein is not a candidate for long-range atmospheric transport. The estimated reaction rate constant for the reaction of OH radicals with acrolein in water is k(OH)=6.52 x 10E9 (1/(M x s). Assuming a OH radical concentration in water in the range between 1 x 10E-15 and 1 x 10E-18 M and taking into account the calculated reaction rate constant the half-lives can be calculated using the equation t1/2=0.69/k(OH) x OH concentration. The calculations yielded half-lives t1/2 in the range between 30 and 30000 h. Photolysis in water is low. No information are available in respect to the phototransformation in soil.

Acrolein does not contain any hydrolysable groups, but it does react with water in a reversible hydration reaction to 3-hydroxypropanal (HPA). The half-life for this reaction was found to be 15 hours in sewage water, 45 hours in drinking water and up to 11 days in de-ionised water. Besides this reaction step HPA reacts in a secondary reaction with acrolein to 3,3’-oxydipropionaldehyde, which further reacts to other secondary products. In field studies (irrigation canals) half-life values for the elimination of acrolein between 3 and 7 hours were calculated. Apparently, processes other than hydration, e.g. volatilisation, also contribute to acrolein dissipation in the aquatic environment.

Biodegradation

Despite the lack of a well-performed ready biodegradability test, it is expected that acrolein will be completely mineralised within 3 weeks because of rapid primary degradation of acrolein within 7 days and no stable metabolites are formed. In addition, the outcome of two different QSAR calculations (BIODEG and OECD-model 75; Rorije et al., 1997) also point to the ready biodegradability of the substance. Based on the entire data set on biodegradation and the QSAR estimates, acrolein will be considered in the current risk assessment as ready biodegradable with a biodegradation rate constant of 1 h^-1 (STP).

Insufficient data are available regarding anaerobic biodegradation to establish the significance of this process as a removal mechanism or to determine the rate at which such a process would proceed.

In sediment/water systems, acrolein undergoes hydrolysis, self-oxidation, and biodegradation. Experimental half-lives of 7.6 h and 10 days were determined for aerobic and anaerobic conditions, respectively. An overall reactivity-based half-life is estimated to be between 100 and 300 h. Because of its low organic carbon/water partition coefficient (Koc) and high water solubility, acrolein is not expected to significantly adsorb to suspended solids or sediments, nor are these suspended solids or sediments expected to significantly absorb acrolein from water.

A soil DT50 of 4.2 hours could be used in the exposure assessment of acrolein. However, it should be noted that this value is derived from less reliable data. As a conservative approach the default value of the TGD (30 days) will be used. In the risk characterisation for the terrestrial compartment reference will be made to the measured value of 4.2 hours.

Bioaccumulation

On the basis of the high water solubility and chemical reactivity of acrolein and its low experimentally determined log Kow of -1.10, no bioaccumulation would be expected.

This is confirmed by a study with Bluegill sunfish exposed to 14C-acrolein for 28 days. Although the half-life for removal of the radiolabelled acrolein was more than 7 days indicating a BCF of 344, this does not indicate the bioaccumulation of acrolein per se, but rather incorporation of the radioactive carbon into tissues following the reaction of acrolein with protein sulfhydryl groups or metabolism of absorbed acrolein and incorporation of label into intermediary metabolites.

Similar results were obtained by two studies with plants (Capsium sp. and Lactuca sativa) exposed to acrolein. Rapid reduction of the acrolein concentrations in plant tissue were observed for Capsium sp.. A half-life of 10.3 hours in the tissue of pepper plants was determined. Furthermore in the study with Lactuca sativa exposed to 14C-acrolein very rapid degradation of 14C-acrolein was observed. Acid-hydrolysable metabolic products, although not identified, were detected, suggesting multiple, conjugated polar metabolites of 14C-acrolein or biological components which have incorporated 14C-fragments resulting from further degradation of 14C-acrolein metabolites.

Distribution

Based on the calculated and experimental Koc values (Koc=51-270), acrolein is expected to be moderately to highly mobile in soil. However, there are indications that the adsorption of acrolein to soil (bound fraction) is irreversible.

Henry’s Law constant (calculated: 6.1 Pa x m³/mol at 20°C;. measured: 3.1 Pa x m³/mol at 20°C and 1.22 x 10^-4 atm x m³/mol at 25°C) indicates that volatilisation from surface waters and moisty soil is expected to be high.

Monitoring Data

In the EU Risk Assessment Report measured acrolein concentrations in the environment are tabulated. Acrolein concentrations in air ranging from 0.08 (clean air regions in the world) up to 27,710 mg/m³ (beside exhaust of cars; USSR) are reported for the years 1950 to 1993. Acrolein concentrations in water ranging from 1.5 (rainwater, Japan) to 51,000 mg/l (hazardous waste sites, USA) are reported for the years 1974 to 1990. The evaluation of a data bank (STORET) of the U.S. EPA showed that acrolein could not be detected in any of 331 sediment samples.

In the US ATSDR Report recent monitoring data from North America were reported (1990-2004). In the following a few examples are cited. In 1996, at various monitoring stations average concentrations for acrolein in air, ranging from 0.05 to 3.2 ppb carbon (0.08-5.6 ppbv) with maximum values ranging from 0.5 to 11.46 ppb carbon (0.8-17.82 ppbv) were found. In 1996, the concentrations of acrolein in ambient air averaged 0.20 and 0.12 µg/m³ (0.086 and 0.052 ppb) for urban and rural locations, respectively. Ambient air concentrations of acrolein at the Oakland-San Francisco Bay Bridge Toll Plaza obtained in April 2001 showed differing concentrations between morning and evening measurements. Acrolein concentrations ranged from 0.096 to 0.140 µg/m3 (0.041-0.060 ppb) during the morning commute, which were lower than the concentrations of 0.031-0.047 and 0.058-0.079 μg/m³ (0.013-0.020 and 0.025-0.034 ppb) during two evening monitoring periods taken on consecutive days. Acrolein has been detected in indoor air. The concentrations of acrolein range from 0.05 to 29 µg/m³ (0.02-12 ppb) in residential homes. Acrolein concentrations are found to be typically higher in indoor air when comparing paired indoor/outdoor samples taken at a site. Acrolein has not been found as a contaminant of drinking water. More recently, acrolein has been detected in surface water and groundwater samples collected at 4 and 15 of the 32 hazardous waste sites, respectively, where acrolein has been detected in some environmental medium. Concentrations of acrolein in landfill leachate ranged from 0.07 to 2.1 ppm. In groundwater, the concentrations of acrolein ranged from 0.006 to 1.3 ppm. More recently, acrolein has been detected in soil and sediment samples collected at 1 and 2 of the 32 hazardous waste sites, respectively, where acrolein has been detected in some environmental medium. One soil sample site was found to have an acrolein concentration of 100 ppm. Acolein was detected in other environmental media. Acrolein has been identified in foods and food components such as raw cocoa beans, chocolate liquor, souring salted pork, fried potatoes and onions, raw and cooked turkey, and volatiles from cooked mackerel, white bread, raw chicken breast, ripe Arctic bramble berries, heated animal fats and vegetable oils, and roasted coffee. Trace levels of acrolein have been found in wine, whiskey, and lager beer. Acrolein is a gaseous constituent of tobacco and marijuana smoke, occurring in both mainstream and sidestream smoke.

In the WHO Report monitoring data of Canada are presented. In urban areas, mean concentrations of acrolein in 4- or 24-h samples are generally less than 0.2 µg/m³. Acrolein was detected (detection limit 0.05 µg/m³) in 1597 (or 57%) of 2816 24-h samples collected between 1989 and 1996 under the National Air Pollution Surveillance (NAPS) programme from rural, suburban, and urban locations (n = 15) in five provinces. The mean concentration in all samples was 0.18 µg/m³ (seven urban sites: 0.05 µg/m³ up to 2.47 µg/m³;  two suburban: up to 1.85 µg/m³; two rural sites: up to 0.33 µg/m³). The highest mean concentration of acrolein in air measured weekly over any three consecutive months during the NAPS monitoring between 1989 and 1996 was 1.58 µg/m³. Acrolein was less frequently detected in ambient air collected at rural sites. Mean concentrations at four rural sites considered to be regionally representative generally did not exceed 0.1 µg/m³; maximum concentrations were less than 0.5 µg/m³ in 24-h samples. Acrolein concentrations in indoor air in Canada are about 2- to 20-fold higher than outdoor levels. Acrolein was detected (detection limit 0.05 µg/m³) in all 29 indoor air samples collected from homes in Windsor, Ontario, between 1991 and 1992 (mean concentration: 3.0 µg/m³; range: 0.4 to 8.1 µg/m³. Acrolein was detected (detection limit 0.05 µg/m³) in 3 of 11 samples of indoor air collected in 1993 from homes in residential and commercial areas of Hamilton, Ontario (mean concentration: 1.1 µg/m³; range: 0.05 to 5.4 µg/m³). Acrolein was detected (detection limit 0.43 µg/m³) in 3 of 35 samples of indoor air collected in 1997 from randomly selected homes in the Greater Toronto Area at concentrations of 16, 22, and 23 µg/m³. In monitoring studies conducted between July 1982 and May 1983, acrolein was below the limit of detection (i.e., 0.1 µg/litre) in samples (n = 42) of treated drinking-water collected at 10 municipalities in Ontario. In an extensive survey of municipal drinking-water supplies at 150 locations in the four Atlantic provinces conducted between May 1985 and October 1988, acrolein was not detected (detection limit 1.0 -2.5 µg/litre) in an unspecified number of samples of raw or treated drinking water. Acrolein was not detected (detection limit 0.1 µg/litre) in 42 raw water samples collected from potable water treatment plants in the Great Lakes region during 1982 and 1983. In 1985, acrolein was detected at concentrations of 6.9 and 7.8 µg/litre (detection limit 5 µg/litre) in liquid effluents from two organic chemical manufacturing plants that discharged into the St. Clair River at Sarnia, Ontario. During 1989 and 1990, however, acrolein was not detected (detection limit 4 µg/litre) in the intake water or effluent of these or 24 other organic chemical manufacturing plants in Ontario.

Futher studies (published between 2000 and 2008) dealing with the occurrence of acrolein in air are available. In 1996, acrolein was detected in samples from two rural sites in the central part of Portugal in a maximum concentration of 1.3 ppb (ca. 3 µg/m³). Throughout 1999-2001, ambient air concentrations were measured in the yards of 87 residences in the city of Elizabeth, NJ. Mean acrolein concentrations of 1.87 (n=22; spring), 1.03 (n=43; summer), 0.40 (n=41; fall), and 0.69 µg/m³ air (n=32; winter) were detected in yards of 87 residences in the city of Elizabeth, NJ. Acrolein was present in 59.4% of the samples in concentrations above the detection limit. Acrolein concentrations were generally higher in spring and fall which is attributed to the higher ambient temperatures and in consequence the higher photochemical activity under these conditions. Traffic sources were identified to contribute significantly to the ambient acrolein levels at residences. In 2001 -2002, VOC emissions of typical tree species from a temperate warm Atlantic rainforest inside the metroplitan area of Sao Paulo (Brazil) were collected. For the samples collected from the rainforest area, an acrolein emission rate of 0.073 µg C/g x h for Cecrupia pachystachia Trecul. was determined. No acrolein emissions were detected in tree samples (Cecrupia pachystachia Trecul.; Casearia sylvestris Sw.; Croton floribundus Spreng.; Solanumerianthum) from the sub-urban area . For plant samples collected on the campus of the University of Sao Paulo, acrolein emission rates of 0.031 (Alchornea sidifolia Müll.) and 0.011 (Syagrus romanzoffiana) µg C/g x h were determined (acrolein was not detected in Casearia sylvestris Sw. and Ficus insipida Willd.). For Ficus benjamina (exotic tree occurring in a large amount in the urbanized areas of Sao Paulo), an acrolein emission rate of 0.057 µg C/g x h was measured for the potted tree whereas no acrolein was detected in F. benjamina held in soil. In 2002, indoor air samples were collected from 59 houses in Prince Edward Island (Canada). Acrolein was detected in concentrations ranging from 0.1 (min) to 4.9 µg/m³ air (max). The geometric and arithmetic mean were determined to be 1 and 1.3 µg/m³, respectively. The acrolein concentrations were elevated in houses built 1970 -1985, in homes with smokers and in those in which carpets had been installed in the past 3 months. In 2006, indoor and outdoor concentrations of acrolein were measured in nine homes in three different California counties and in a number of unoccupied, newly constructed houses. Acrolein concentrations ranging from 2.1 to 7.8 (a.m.; average: 4.0 µg/m³) and 3.1 to 12.2 µg/m³ (p.m.; average: 6.0 µg/m³) were found in indoor air of the 9 residential homes whereas the outdoor concentrations were determined to be in the range from 0.09 to 1.7 (a.m.; average: 0.58 µg/m³) and 0.15 to 1.7 µg/m³ (p.m.; average: 0.62 µg/m³). In unoccupied houses, acrolein concentrations ranging from 3.0 to 5.5 µg/m³ (a.m.) were found in indoor air whereas outdoor concentrations were determined to be in the range from 0.31 to 0.84 µg/m³ (a.m.). In unoccupied homes elevated acrolein concentrations were detected in houses with furniture (average without: 3.1 µg/m³; average with: 5.0 µg/m³). The emission concentrations of carbonyl compounds (e.g. acrolein) in air were determined from a total of 195 man-made source units within 77 individual companies at a large industrial complex in Korea (Ban-Wall and Si-Hwa Industrial Complex in the city of An-San and Si-Hung). Acrolein concentrations ranging from 0.07 (min) to 66.8 µg/m³ air were detected in samples collected between 2004 and 2005. At eight workplaces air samples were collected during frying/grilling of meat or fish or during deep-frying, at stationary sampling points close to the cooking apparatus and the active working area. Acrolein concentrations ranging from 0.01 to 0.59 mg/m³ were detected in eight workplaces of bakeries, food factory and five restaurant kitchen during cooking. The highest concentration as measured in a restaurant where fish was fried in butter and oil at a temperature of about 200°C.