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Environmental Release, Fate and Effects
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- Emissions to water and soil
- Soil and sediment
- Effects on organisms in the environment
- Aquatic organisms Fish
- Aquatic invertebrates
- Algae and aquatic plants
- Terrestrial organisms
- Micro-organisms
Environmental Release, Fate and EffectsFormaldehyde occurs naturally in the atmosphere and biosphere, where it is released through a variety of biological and chemical processes. The most important process responsible for natural background concentrations of formaldehyde in the environment is the photochemical oxidation of atmospheric methane. Other processes responsible for release of formaldehyde to nature are reactions of hydroxide radicals (OH) with terpenes and isoprene emitted from the foliage of plants, direct emission of formaldehyde during decomposition of organic matter (Martin et al. 1999), photochemical production of formaldehyde in snowpack, and direct emissions from algae living in the snow (Sumner and Shepson, 1999). Formaldehyde occurs naturally in plants and animals (IARC 1995). A wide range of human domestic and industrial activities is responsible for both direct and indirect releases of formaldehyde into the atmosphere from diffuse and point sources. Emission from fuel combustion is perhaps the single most important anthropogenic source of atmospheric formaldehyde, with formaldehyde being released directly or subsequently formed by oxidation of higher alkanes, hydrocarbons, or other precursors, released from combustion processes (Lowe et al. 1980). Release of formaldehyde into the atmosphere or aquatic environment may also occur during its manufacture, or when used as an intermediate in manufacturing, and during use of products containing formaldehyde.
Recent data from the Australian National Pollution Inventory (NPI) database for emissions of formaldehyde indicate that almost all formaldehyde is released to the atmosphere, with total emissions estimated to be 7150 tonnes for the year 2002-2003 compared with 6600 tonnes for the year 2001-2002. Figure 8.1 is a summary of the atmospheric emissions estimates by source category. For the estimation methods, refer to the relevant NPI Emissions Estimation Technique Manuals, which are available on the NPI website (NPI, 2005a). The estimates include aggregated emissions estimates reported by state government departments and data reported by industry from individual industrial facilities (labelled ‘industry emissions’). Aggregated emissions are derived from domestic, mobile and non-industrial facilities, and from smaller industrial facilities not meeting the thresholds criteria for industry reporting, while industry emissions are derived from a large number of industrial activities emitting above- threshold levels of formaldehyde. The threshold criteria is use of ≥10 tonnes of formaldehyde per year, where “use” is defined as the handling, manufacture, import, processing, coincidental production, or other uses. Figure 8-1: Annual formaldehyde atmospheric emissions for (a) 2001-2002 and (b) 2002-2003 (NPI). 
The NPI data indicate that most of the atmospheric emissions of formaldehyde occur through combustion processes from diffuse sources. The primary combustion activities are burning of domestic fuel and transportation. The domestic fuel category includes burning solid and liquid fuels and gas for domestic heating and cooking, and lawn mowing. The transportation category includes emissions from motor vehicles, rail transport, recreational boating, commercial shipping, and air transport. Formaldehyde emissions from industrial facilities are predominantly point source emissions including both direct emissions of vapour and emissions from fuel combustion. According to the NPI estimates, point source emissions from industrial activities contributed about 16% of the total formaldehyde emissions for 2001-2002 (1085 of 6600 tonnes) and around 14% for 2002-2003 (1022 of 7150 tonnes). Miscellaneous combustion and miscellaneous activities also contribute diffuse and point source emissions of formaldehyde. The miscellaneous combustion category includes burning of vegetation for fuel reduction, regeneration, agricultural management, and wildfires, in addition to fuel combustion from sub- reporting threshold industrial and commercial facilities, and cigarette smoking. Miscellaneous activities include direct vapour emissions and fuel combustion from use of domestic and commercial aerosols, operation of agricultural machinery, and contributions from the operation of schools, laundries, bakeries, pubs and other small business enterprises.
Emissions of formaldehyde to water and soil may be expected to occur via sewage treatment facilities during manufacture of formaldehyde and formaldehyde products and during use of products containing formaldehyde, including consumer products. However, formaldehyde emissions to water and soil are significantly less than emissions to the air. Emissions data from the NPI indicate only about 1000 kg of formaldehyde was released into water and/or onto land from point sources in the reporting year 2001-2002 and only 5 kg in 2002-2003. No distinction was made between amounts released to soil and that to water. Formaldehyde is present in low concentrations (the majority < 0.2%) in a wide variety of consumer products. These products include household cleaning products, such as dishwashing liquids, disinfectants, fabric conditioners, and cosmetics products, such as shampoos, conditioners, and shower gels etc. (Section 7.3.3). Many of these products are released directly into wastewater streams during their use, and hence are a diffuse source of formaldehyde, which may contribute to formaldehyde levels in water. Formaldehyde emissions to soils are most likely to occur through disposal of solid wastes containing formaldehyde. A number of companies indicated that they disposed of small amounts of solid waste containing formaldehyde (mainly solidified resin waste and sludge from on-site treatment facilities) into landfill.
This section summarizes the environmental fate of formaldehyde, emphasizing the atmospheric fate, as more than 99% of formaldehyde is released to air, with only small amounts being released to water and soil. The information is derived from the published literature and a number of peer-reviewed reports on formaldehyde. The latter include US EPA (1993), IPCS (1989), IPCS (2002), and the Canadian Priority Substance List report (Environment Canada, 2001). Data cited from existing reports are referenced as such and not necessarily by the original authors of the particular studies.
In the atmosphere, formaldehyde has a high degree of chemical reactivity and is capable of undergoing a wide variety of chemical reactions (Section 5). However, the major mechanism of destruction of formaldehyde is by photolysis. Less important removal mechanisms are reactions with photochemically produced OH radicals and other trace substances, including nitrate (NO3) and hydroperoxyl (HO2) radicals, hydrogen peroxide (H2O2), ozone (O3), and chlorine (Cl2), and all classes of hydrocarbon pollutants (Atkinson, 1990). The oxidation of formaldehyde with OH radicals proceeds primarily by H-atom abstraction, forming formyl (HCO) radicals, which then rapidly react with O2 to form carbon dioxide (CO2) and hydroperoxyl (HO2) radicals. Other products formed during these reactions include water, formic acid, carbon monoxide (CO), and hydroperoxyl/formaldehyde (HCO3) adduct (US EPA, 1993). During direct photolysis, formaldehyde absorbs UV radiation from below 290 nm to about 340 nm. The dominant photolytic pathway produces stable molecular hydrogen (H2) and carbon monoxide (Atkinson et al., 1990; Lowe et al., 1980). A second photolytic pathway produces an HCO radical and a hydrogen atom, both of which react quickly with oxygen to form hydroperoxyl radicals and carbon monoxide (US EPA, 1993). Formaldehyde is an important precursor in smog formation in the urban atmosphere, where it reacts with nitrogen oxides and other compounds to eventually form ozone, peroxyacetyl nitrate and other compounds. The daytime half-life of formaldehyde in ambient air is generally short. The calculated half-life of formaldehyde with respect to photolysis is about 4 hours, and to reactions with OH radicals is 1.2 days. Reactions with NO3 radicals and O3 are slower, with the half-life times for NO3 reactions of 80 days, and for ozone reactions of > 4.5 years (Atkinson, 2000; US EPA, 1993). The atmospheric residence time of formaldehyde varies with the availability of hydroxyl and nitrate radicals to react with formaldehyde, which is principally controlled by the season, time of day, intensity of sunlight, temperature and cloud cover. Table 8.1 provides the calculated atmospheric residence times (in hours) of formaldehyde, taking into account gas-phase reactions with OH, NO3, and H2O, photolysis, in-cloud reactions with OH, and wet and dry deposition (US EPA, 1993). During the day, reaction with hydroxyl radicals is an important removal process of formaldehyde when their concentration is high. At night, reaction with nitrate radicals is an important (although slower) removal process, particularly in polluted urban areas where the concentration of nitrate radicals is high (Atkinson, 2000; IPCS, 2002). In the absence of nitrogen dioxide, the half-life of formaldehyde is approximately 50 min during the daytime. In the presence of nitrogen dioxide, this drops to about 35 min (IPCS, 1989). In winter on clear days, residence times of formaldehyde will be longer than in summer because the intensity of sunlight is lower. Because of its high water solubility, formaldehyde is efficiently transferred into clouds and rain, where it can react with aqueous hydroxyl radicals in the presence of oxygen to produce formic acid and hydroperoxide. The formic acid may then be removed in rainfall. Small amounts of formaldehyde may also be removed by dry deposition. The atmospheric residence time of formaldehyde under rainy conditions ranges from minutes in cold climates to a few hours in warm climates (Atkinson, 2000; US EPA, 1993). Table 8.1 shows that wet deposition results in significantly more rapid removal rates of formaldehyde during winter on rainy days. Table 8.1: Seasonal and diurnal variations in the atmospheric residence times of formaldehyde (US EPA, 1993) Weather conditions Time of Day Atmospheric residence times (hours) New York Atlanta Summer Winter Summer Winter Clear sky Day Night 3 17
20-110 90 2 10
20-70 80 Average 5 40 4 20 Cloudy sky Day Night 6 30
18-50 80 3 19
6-8 70 Average 9 50 4 30 Rainy Day Night
3 0.8 3 0.5
2 1.6 3 0.7
Average 3 0.6 2 0.9
Formaldehyde is highly water soluble, with a solubility of up to 550 g/L at 25C. Concentrations as high as 95% formaldehyde in water are obtainable if suitable temperatures are maintained and methanol and other substances are added as stabilizers (IPCS, 1989). The concentrations of formaldehyde in formalin solutions manufactured in Australia range from 37% to 54%. In dilute aqueous solutions, formaldehyde exists almost exclusively in the hydrated gem-diol form [CH2O + H2O ↔ CH2(OH)2], while at higher concentrations formaldehyde forms other species, such as methylene glycol, polyoxymethylene and hemiformals (Environment Canada, 1985; Dong & Dasgupta, 1986). Most aqueous formaldehyde released into water is expected to remain dissolved in the aquatic compartment where it would enter sewage treatment facilities. While the vapour pressure of formaldehyde indicates a high volatility (516 kPa at 25C), the Henry’s Law Constant (0.022-0.034 Pa.m3/mol) indicates only a moderate volatility from water (Mensink et al., 1995). Limited degradation data are available. It is expected that formaldehyde will be degraded relatively rapidly in sewage treatment plants and in surface water. Formaldehyde does not contain any hydrolysable groups, and hence hydrolysis will not be a degradation pathway. However, at low concentrations, formaldehyde is readily biodegradable, with 90% degradation reported in a closed bottle test (at 2-5 mg/L) after 28 days (Gerike & Gode, 1990). Howard et al. (1991) estimate 57% to 99% removal from sewage treatment plants with secondary treatment. The aqueous anaerobic half-life times are predicted to be from 1 to 7 days in unacclimated sludge. The estimated half-life times in surface water are 24-168 hours, and in groundwater are 48 to 336 hours (Howard et al., 1991).
Limited data are available about the fate of formaldehyde in soil and sediment. Formaldehyde is formed in the early stages of decomposition of plant residues in soils and is degraded by soil bacteria such that accumulation in soil does not occur (IPCS, 1989). The high water solubility and low partition coefficient (maximum Log Kow of 0.35) indicates a low potential for adsorption onto suspended sediments in the soil solution or in aqueous environments. Aqueous solutions of formaldehyde released into soil through spills or disposal would be expected to infiltrate into the soil, from where it may leach into surface and ground water. However, since formaldehyde is susceptible to biodegradation by a range of micro-organisms, it is expected to be readily degraded, and not accumulate. Howard et al. (1991) estimates a soil half-life of 24 to 168 hours, based on the estimated aqueous aerobic biodegradation half-lives.
Formaldehyde occurs naturally in plants and animals, and is readily metabolised by organisms. The measured Log Kow indicates a low potential for bioaccumulation. This is confirmed by negative results of bioaccumulation studies with shrimp and fish showing no bioaccumulation of formaldehyde (OECD, 2002). A bioconcentration factor of 0.19 has been calculated based on a log octanol/water partition coefficient of 0.65 (IPCS, 2002).
The ecotoxicity data presented here are summarized from existing reports on formaldehyde, on-line computer databases, and the published literature. Due to the large volume of data, for example, 655 records in the US EPA ECOTOX (US EPA, 2002) database, predominantly for aquatic organisms, not all studies have been evaluated. A recent paper by Hohreiter and Rigg (2001) highlights the poor reliability and quality of much of existing data on the aquatic toxicity of formaldehyde (the same can be said for the terrestrial toxicity data). The main criticisms were a lack of analytical confirmation of the concentrations of formaldehyde (most endpoints being reported as nominal concentrations), and the lack of GLP compliance (many of the studies were conducted prior to the introduction of GLP). A further criticism was the lack of available chronic toxicity data. Where possible, any anomalous or unreliable data are indicated.
The US EPA ECOTOX database (US EPA, 2002) lists acute toxicity endpoints of formaldehyde for a large number of fish species. Many of these endpoints appear to be derived from non-standard tests. The 96-hour test data show that formaldehyde is practically non-toxic to fish, with most species listed having lethal concentration (LC50) values above 100 mg/L. The lowest recorded 96-hour LC50 in the database is 1.51 mg/L for Bluegill sunfish (Lepomis macrochirus). However, the original source of the latter endpoint is uncertain. The reference indicates the data is from the Environmental Effects Database, Office of Pesticide Programs of US EPA. The Hohreiter and Rigg review (2001) suggests that acute toxicity endpoints do not vary greatly between fish species. In their review of the most reliable existing data, striped bass (Morone saxatilis) is indicated to be the most sensitive fish species, with adjusted mean (to formaldehyde concentration) 96-h LC50 values of 16.9 mg/L (range 7.26 mg/L to 24.44 mg/L, of 13 endpoints). The most resistant fish species to formaldehyde are rainbow trout, with LC50 values of 58.7 mg/L, and Atlantic salmon with LC50 values of 69.8 mg/L. Fajer-Ávilla et al. (2004) have recently reported a study of the effects of formalin on bullseye puffer fish (Sphoeroides annulatus Jenyns, 1843). The replicated static study determined a 72-hour LC50 of 79 mg/L based on measured concentrations. The study also reported sublethal effects, including immobility and slow reaction to external stimulation, in the concentration range 24 mg/L to 103 mg/L. At concentrations above 75 mg/L, the test fish showed glassy exophthalmic eyes with an opaque film after 13 hours and haemorrhages in fins and eyes by 20 hours. Effects on the epithelial structure and mucous cell densities in rainbow trout (Onchorhyncus mykiss) have also been reported at concentrations between 50 ppm and 300 ppm (Buchmann et al., 2004). Recent replicated static renewal studies with 7-day-old fathead minnow (Pimephales promelas) and conducted according to GLP indicated 96-hour LC50 and median effective concentration (EC50) (lethality and behavioural effects) values of 27.2 mg/L (Hohreiter & Rigg, 2001). AmphibiansThe responses of various species of amphibians are similar to those of fish, with median acute LC50 ranging from 10 mg/L to 20 mg/L for a 72-hour exposure. For example, leopard frog tadpoles (Rania pipiens) had a 72-hour LC50 value of 8.7 mg/L, and toad larvae had a 72-hour LC50 value of 18.6 mg/L. The available data indicate that tadpoles are more sensitive to formaldehyde than most species of fish and aquatic invertebrates. No data are available on long-term aquatic studies (IPCS, 1991; Hohreiter and Rigg, 2001).
Unlike fish, aquatic invertebrates show a wide range of responses to formaldehyde. Available acute toxicity endpoints [adjusted by Hohreiter and Rigg (2001) to reflect formaldehyde content] indicate a range of 96-hour LC50 values between 0.42 mg/L for the seed shrimp (Cypridopsis sp.) and 337 mg/L for backswimmers (Notonecta sp.). Data in the US EPA ECOTOX database (US EPA, 2002) show EC50 values for mussels (Mytilus edulis) ranging between 5 mg/L and 60 mg/L. Hohreiter and Rigg (2001) list adjusted endpoints for molluscs (Corbicula and Helisoma sp) of between 35 mg/L and 50 mg/L. The above data indicate that the seed shrimp is the most sensitive organism. However, Hohreiter and Rigg (2001) believe this endpoint (attributed to Bills et al. 1977) is anomalous. More recent replicated tests, performed under standard conditions with analytical confirmation of nominal formaldehyde concentrations, indicate much higher 96-hour EC50 values of 54.4 mg/L to 68.6 mg/L for Cypridopsis. The NOEC is 18.8 mg/L (measured) for both survival and reproduction, and the LOEC is 50 mg/L. The most sensitive species attained from the most reliable endpoint for invertebrates reviewed in Hohreiter and Rigg (2001) is 5.8 mg/L for Daphnia pulex (96-hour EC50). Available data indicate formaldehyde is slightly to moderately toxic to Daphnia. In the US EPA ECOTOX database (US EPA, 2002), the 48-hour EC50 values reported for the water flea (Daphnia magna) ranged between 14 mg/L and 58 mg/L. Recent replicated tests reported by Hohreiter and Rigg (2001) showed comparable values, with 48-hour static acute LC50 values of 9.45 mg/L for Ceriodaphnia dubia and 14.75 mg/L for Daphnia pulex. Chronic toxicity of formaldehyde to Ceriodaphnia dubia in two 7-day tests for immobility and mortality gave NOEC and LOEC values of 3.0 mg/L and 6.0 mg/L, and 1.0 mg/L and 3.0 mg/L, respectively. The geometric mean of each test provide two chronic values of 4.24 mg/L and 1.73 mg/L, respectively (Hohreiter and Rigg, 2001). Algae and aquatic plantsOnly a limited number of studies have been carried out to evaluate the toxicity of formaldehyde to aquatic plants. In general, these data suggest that formaldehyde is slightly to moderately toxic to aquatic plants. However, much of the data is difficult to evaluate owing to the non-standard test methods used. The SIAR (OECD, 2002) indicates the toxic threshold (192 hours) of formaldehyde to Scenedesmus quadricauda in a static cell multiplication inhibition test using an aqueous solution of formaldehyde (35% solution) is 0.88 mg/L. The toxic threshold is defined in the cited investigation as the concentration of the test substance causing 3% inhibition of cell multiplication compared to untreated controls. The IPCS Report (1991) lists a 24-hour LC50 value of 0.4 mg/L for Scenedesmus sp. The US EPA ECOTOX database (US EPA, 2002) lists the following LOEC and NOEC values for algae: Blue-green algae (Microcystis aeruginosa) = 0.39 mg/L, Brown algae (Phyllospora comosa) = 0.1 mg/L to 10 mg/L; and Green algae (Scenedesmus quadricauda) = 0.3 mg/L to 2.5 mg/L. Most of these data are for 4 to 8 day tests, and are therefore not standard endpoints. Hohreiter and Rigg (2001) did not estimate a final value for aquatic plants because most of the data they reviewed did not meet US EPA requirements. However, they believe that criteria protecting aquatic animals should also adequately protect aquatic plants.
Relatively few data are available on the toxicity of formaldehyde to terrestrial organisms. The US EPA ECOTOX database (US EPA, 2002) lists only 11 records for terrestrial organisms including plants, and with only two studies on birds. For the majority of these records, no endpoints are reported. The studies on birds indicate that formaldehyde is practically non-toxic to Mallard duck (Anas platyrhynchos) and Northern bobwhite quail (Colinus virginianus), with the Mallard having an 8-day LC50 > 5000 ppm, and the Northern bobwhite having an 8 day LC50 > 5000 ppm and a 14 day LD50 of 790 mg/kg. Several studies cited in the CICAD (IPCS, 2002) indicate potentially adverse effects on terrestrial plants after exposure to formaldehyde in air and fog. Bean plants (Phaseolus vulgaris) exposed to formaldehyde in air at concentrations between 65 ppb to 365 ppb for up to 4 weeks exhibited no short-term effects, but showed an imbalance in shoot and root growth, which could increase the vulnerability of plants to environmental stresses, such as drought. Plants exposed to formaldehyde in fog water for 40 days (4.5 hour/night, 3 nights/week) at concentrations equivalent to 18 g/m3 and 54 g/m3 (14.9 ppb and 44.8 ppb) showed a range of potentially adverse effects. Rapeseed (Brassica rapa) exhibited a reduction in leaf area, leaf and stem dry weight, and flower and seedpod numbers, while slash pine (Pinus elliotti) exhibited an increase in needle and stem growth. Wheat (Triticum aestivum) and aspen (Populus tremuloides) exposed to formaldehyde in fog during the study exhibited no effects. Pollen germination has been shown to be sensitive to some air pollutants. Pollen grains of Lilium longiflorum, sown in a straight line on a culture medium, were exposed separately for one, two, and five hours to formaldehyde gas at concentrations of 0.44 mg/m³ (0.35 ppm) and 2.88 mg/m³ (2.3 ppm). Grains exposed to the lower concentration for five hours showed a significant reduction in pollen-tube length, whereas a one- or two-hour exposure time had no effect. Pollen grains exposed to formaldehyde concentrations of 2.88 mg/m³ showed a decrease in tube length after one hour of exposure (IPCS, 1989).
Formaldehyde is toxic to a range of micro-organisms and is known to kill viruses, bacteria, fungi, and parasites when used at relatively high concentrations. Consequently, it has long been employed as a disinfectant and parasiticide in many industries. For example, in Australia, formaldehyde is commonly used for the control of fungal infections, protozoan and metazoan ectoparasites in aquaculture systems, and as a general disinfectant in animal husbandry situations. Unicellular micro-organisms, such as algae and protozoa appear to be most sensitive to formaldehyde, with acute lethal concentrations ranging from 0.3 mg/L to 22 mg/L. Various species of microscopic fungi including Aspergillus, Scopulariopsis and Penicillium crustosum are also sensitive to formaldehyde gas, with 100% of spores exposed to 2 ppm of gaseous formaldehyde reported to be killed within 24 hours (IPCS, 1989). A few studies summarized in the IPCS (1989) report indicate formaldehyde can negatively impact soil microbial biomass and activity. One study reports that formaldehyde was able to inhibit the enzyme which catalyses deamination of the amino acid L-histidine, an important nitrogen source for plants and microbes. Another study reported a significant reduction in bacterial populations in soils near industrial sites polluted with formaldehyde and in soils on sites using urea- formaldehyde fertilizers. Several studies also cited in the IPCS report (IPCS, 1989) indicated some strains of bacteria (e.g. Psuedomonas) are able to utilize formaldehyde as a carbon source. Sewage micro-organisms were inhibited at 30 mg/L in a Closed Bottle test suggesting that sewage treatment plant performance would only be impaired at relatively high concentrations of formaldehyde (Gerike and Gode, 1990). There is some evidence that certain soil mesofauna may be adversely affected by formaldehyde. The IPCS (1989) report indicated that nematodes in peat were killed by application of formalin (37% formaldehyde solution) at 179 mL/m³. However, in another study, cereal cyst nematode populations significantly increased following soil treatment with formalin, presumably due to suppression of fungal parasites, which attack the nematodes.
For aquatic organisms (Table 8.2), the available data indicate daphnia to be the most sensitive species, with EC50 of 5.8 mg/L. The most sensitive fish species is striped bass, with mean LC50 values of 16.9 mg/L. The responses of various species of amphibians are similar to those of fish, with LC50 ranging from 10 mg/L to 20 mg/L. While no EC50 endpoints are available, the data suggest that formaldehyde is only slightly to moderately acutely toxic to aquatic plants and algae. Table 8.2: Summary of the most sensitive aquatic species to formaldehyde based on acute toxicity endpoints Aquatic organisms Species Endpoint Fish Striped bass (Morone saxatilis) 96-h LC50 = 16.9 mg/L
Amphibians Rania pipiens 72-h LC50 = 8.7 mg/L Aquatic invertebrates Daphnia pulex 96-h EC50 = 5.8 mg/L Molluscs Corbicula sp 96-h EC50 = 35 mg/L Algae Freshwater green algae No reliable data For terrestrial organisms (Table 8.3), the available data indicate that formaldehyde is practically non-toxic to birds exposed to formaldehyde in food. Formaldehyde in air and fog water has potentially adverse effects on some plant species when exposed. The lowest effect concentration of formaldehyde in air was 65 ppb and 14.9 ppb in fog. Gaseous formaldehyde also kills the spores of microscopic fungi within 24 hours at concentrations of 2 ppm. Pollen grains of Lilium longiflorum, exposed to 0.35 ppm of formaldehyde gas showed a significant reduction in pollen-tube length after 5 hours. Pollen grains exposed to formaldehyde concentrations of 2.3 ppm showed a decrease in tube length after 1 hour of exposure. Table 8.3: Summary of the effects of formaldehyde on terrestrial organisms Terrestrial organisms Effects Endpoint Northern bobwhite quail (Colinus virginianus) 14-d LD50 790 mg/kg
Bean plants (Phaseolus vulgaris) Imbalance in shoot and root growth after up to 4 weeks exposure 65 ppb (fog) Rapeseed (Brassica rapa) Reduction in leaf area, leaf and stem dry weight, and flower and seedpod numbers
after 5 hours 14.9 ppb (fog) 0.35 ppm (gas) Microscopic fungi (Scopulariopsis and Penicillium) 100% mortality in 24 hours 2 ppm (gas)
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