Endocrine Disruptors

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Fate and Transport in the Environment

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Fate and Transport of Endocrine Disruptors in the Environment

Since endocrine disrupting chemicals (EDCs) are substantially diverse in character, vary widely in physical and chemical properties, how they are used, as well as how they exist in the environment, discussion of fate and transport is very difficult unless the chemicals are categorized in some manner.

A basic list of widespread pollutants with known endocrine disrupting effects has been published by www.ourstolenfuture.org. The categories outlined at this website include the following 95 known Endocrine Disruptors:

1) Persistent Organohalogens (10)
2) Food Antioxidants (1)
3) Pesticides (57)
4) Phthalates(4)
5) Metals (4)
6) Others (10)

Although EPA estimates that there are potentially approximately 87,000 chemicals to be screened for EDC effects, including 75,500 industrial chemicals, 900 pesticide active ingredients, 2,500 other pesticide ingredients, and 8,000 cosmetics, food additives and nutritional supplements, only the fate and transport of the 95 known endocrine disrupting chemicals will be discussed here.

Foundation Of The Fate & Transport Concept
The term “Fate and Transport” refers to the outcome of a contaminant in the environment as a result of its potential to be transported, transformed (physically, chemically, or biologically), or accumulated in one or more media.

As described in Risk Assessment Guidance for Superfund, part A (EPA, 1989), there are several important considerations for determining environmental fate and transport of chemicals of concern, i.e. “Endocrine Disruptors”, in the environment. They include:

  • What are the principle mechanisms for change or removal in each of the environmental media?
  • How does the chemical behave in air, water, soil, and biological media? Does it bioaccumulate or biodegrade? Is it absorbed or taken up by plants?
  • Does the agent react with other compounds in the environment?
  • Is there inter-media transfer? What are the mechanisms for inter-media transfer? What are the rates for inter-media transfer or reaction mechanism?
  • How long might the chemical remain in each environmental medium? How does its concentrations change with time in each medium?
  • What are the products into which the agent might degrade or change in the environment? Are these products potentially of concern?
  • Is a steady-state concentration distribution in the environment or in specific segments of the environment achieved?

Physical & Chemical Properties Of EDCs

The environmental fate and transport of a contaminant is controlled by the compound’s physical and chemical properties and the nature of the media through which the compound is migrating. Specific physical/chemical parameters of interest include:

  • Koc – organic carbon-water partition coefficient
  • Kd – soil/sediment-water partition coefficient
  • Kow – octanol-water partition coefficient
  • Solubility – upper limit on a chemical’s dissolved concentration in water at a specified temperature.
  • Henry’s Law Constant – air-water partition coefficient
  • Vapor Pressure – pressure exerted by a chemical vapor in equilibrium with its solid or liquid form at any given temperature.
  • Diffusivity – movement of a molecule in a liquid or gas medium as a result of differences in concentration.
  • Bioconcentration Factor – the extent of chemical partitioning at equilibrium between a biological medium (i.e. fish tissue) and an external medium (i.e. water). Bioaccumulation can occur through bioconcentration and biomagnification. Bioconcentration in aquatic biota is the passive diffusion of a chemical from the respiratory surface to the organism, specifically the fat tissues, resulting in higher concentrations in the organism than in its surrounding environment. Biomagnification is the absorption of a chemical by an organism as a result of their diet, despite the concentration of the chemical being lower in the food than in the organism.
  • Media-specific Half Life – relative persistence of a chemical in a given medium.

Physical and chemical properties are presented in tables for each of the EDC categories. The parameters, Log Kow, Solubility, Henry's Law Constant, Vapor Pressure, Bioconcentration Factor, and Half-lives, are presented in the tables as listed in the Superfund Chemical Data Matrix (SCDM), Office of Emergency and Remedial Response, (1997).


The parameters, Koc, Kd, and Diffusivity, are presented in the tables as listed in the Environmental Protection Act Soil Screening Guidance, Part 5, EPA540/R-96/018, (1996).

1) PERSISTENT ORGANOHALOGENS

Persistent organohalogens have been detected in biota worldwide. They are generally lipophilic, persistent, and bioaccumulate both in the environment and at each trophic level of the food chain. Bioavailability in the aquatic environment depends on whether the compound is soluble in water or bound to particle. Generally, when the log Kow is greater than 5-6, the chemical is highly lipophilic and both bioconcentration and biomagnification can occur. This is the case for several organohalogens.

Specific physical and chemical properties of a subset of persistent organohalogens, known to be important in evaluating fate and transport, are presented below. A table of the associated with the physical and chemical properties for this EDC category follows.

1,2-DIBROMOETHANE

TERRESTRIAL FATE: Biodegradation can be a primary degradation process in soil. A review of available biodegradation data pertaining to 1,2-dibromoethane concluded that it is biotransformed fairly readily in the environment; lifetimes can be as short as several days in surface soils and as long as many months in aquifer materials. Persistence can vary greatly from soil to soil. Koc values and detection in various ground waters indicate that 1,2-dibromoethane will leach in soil. The relatively high vapor pressure (13 Torr) indicates evaporation will occur from soil surfaces.

AQUATIC FATE: The primary removal process for 1,2-dibromoethane in surface water is volatilization. A review of available biodegradation data pertaining to 1,2-dibromoethane concluded that it is biotransformed fairly readily in the environment, although the rate of biodegradation can be slow (half-life of 180 days). In ground waters (such as aquifers) where volatilization does not occur, 1,2-dibromoethane can be degraded by biodegradation and hydrolysis.

ATMOSPHERIC FATE: Based upon a vapor pressure of 13 Torr, 1,2-dibromoethane is expected to exist primary in the vapor-phase in the ambient atmosphere. Vapor-phase 1,2-dibromoethane will degrade in the ambient atmosphere by reaction with photochemically produced hydroxyl radicals. Direct photolysis is not expected to be important in fate and transport.

CHLOROFORM

TERRESTRIAL FATE: When spilled on land, chloroform would be expected to evaporate rapidly into the atmosphere due to its high vapor pressure (200 Torr). It is poorly adsorbed to soil, especially in situations where the soil has low organic carbon content. Chloroform can readily leach into the groundwater.

AQUATIC FATE: When released into water, chloroform will be primarily lost by evaporation into the atmosphere. Little chloroform will be adsorbed to sediment.

ATMOSPHERIC FATE: Chloroform released to the atmosphere will degrade by reaction with hydroxyl radicals. It will be transported long distances and will partially return to earth in precipitation.

DIOXINS (2,3,7,8-TCDD)

TERRESTRIAL FATE: TCDD does not leach. Movement by surface erosion of soil particles or flooding may be possible. TCDD exposed to sunlight on terrestrial surfaces may be susceptible to photodegradation. Volatilization from soil surfaces during warm, summer months may be a major mechanism by which TCDD is removed from soil. Volatilization during cold, winter months or from soil depths several centimeters below the boundary layer is extremely slow. Various biological screening studies have demonstrated that TCDD is generally resistant to biodegradation.

AQUATIC FATE: Due to its very low water solubility, most of the 2,3,7,8-TCDD occurring in water is expected to be associated with sediments or suspended material. Aquatic sediments may be an important, and ultimate, environmental sink for all global releases of TCDD. Two processes that may be able to remove TCDD from water are photolysis and volatilization. Many bottom sediments may therefore not be susceptible to significant photodegradation. Various biological screening studies have demonstrated that TCDD is generally resistant to biodegradation. TCDD has been shown to bioconcentrate in aquatic organisms.

ATMOSPHERIC FATE: Although 2,3,7,8-TCDD has an extremely low vapor pressure, it has been shown to be volatile and to occur in air in both the gas-phase and particulate-phase. Sufficient data are not currently available to estimate the potential photolysis rate of particulate-phase TCDD. TCDD particulates may be physically removed from the atmosphere by wet and dry deposition. Monitoring data have indicated that TCDD may be transported long distances through the atmosphere.

PCBS

TERRESTRIAL FATE: The environmental fate of PCBs is dependent on the degree of chlorination in the specific congener mixture. In general, the persistence of PCB congeners increases with an increase in the degree of chlorination. PCBs are resistant to biodegradation. Although biodegradation of PCBs may occur very slowly on an environmental basis, no other degradation mechanisms have been shown to be important in soil systems; therefore, biodegradation may be the ultimate degradation process in soil. The Koc value (309000 l/kg) indicates that PCBs will be tightly adsorbed in soil with adsorption generally increasing as the degree of chlorination of the individual congeners increase. PCBs should not leach significantly in most aqueous soil systems although the most water soluble PCBs will be leached preferentially. In the presence of organic solvents, which may be possible at waste sites, PCBs may have a tendency to leach through soil. Although the volatilization rate of PCBs may be low from soil surfaces due to the tight adsorption, the total loss by volatilization over time may be significant because of the persistence and stability.

AQUATIC FATE: Higher chlorinated congeners in PCBs are susceptible to reductive dechlorination by anaerobic microogranisms found in aquatic sediments. Although biodegradation of higher chlorinated congeners may occur very slowly in the environment, no other degradation mechanisms have been shown to be important in environmental aquatic systems; therefore, biodegradation may be the ultimate degradation process in natural water. In water, adsorption to sediments and organic matter is a major fate process for PCBs. The PCBs with the highest vapor pressure (low chlorination) will be enriched in the air. Strong PCB absorption to sediment significantly decreases the rate of volatilization. Although the volatilization rate may be low, the total loss by volatilization over time may be significant because of the persistence and stability of the PCBs. Aquatic hydrolysis and oxidation are not important processes with respect to PCBs. PCBs have been shown to bioconcentrate significantly in aquatic organisms.

ATMOSPHERIC FATE: The vapor pressures of the PCB congeners indicate that they will exist primarily in the vapor phase in the ambient atmosphere with enrichment of PCBs with enrichment of PCBs with the highest vapor pressures (low chlorination) although a relatively small percentage can be expected to partition to atmospheric particulates. Physical removal of PCBs in the atmosphere is accomplished by wet and dry deposition processes; dry deposition will be important only for the PCB congeners associated in the particulate-phase. The relatively long degradation half-lives in air indicates that physical removal is more important than chemical transformation.

PENTACHLOROPHENOL

TERRESTRIAL FATE: Photolysis and hydrolysis of pentachlorophenol do not appear to be significant processes in soil. Pentachlorophenol released to soil will biodegrade with half-lives of weeks to months. If the pentachlorophenol dissociates in soil, little volatilization will occur but leaching to groundwater is possible (dependent upon pH of soil).

AQUATIC FATE: Pentachlorophenol released to water undergoes photolysis. Biodegradation probably becomes significant after a period of acclimation (may be several weeks). Adsorption to sediments will be considerable. Hydrolysis and volatilization are not important processes in water.

ATMOSPHERIC FATE: Pentachlorophenol has been detected associated with particulate matter in air. Pentachlorophenol will be lost by gravitational settling. Vapor phase pentachlorophenol will be lost by photolysis and to a leasser extent, reaction with photohchemically produced hydroxyl radicals.


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2) FOOD ANTIOXIDANTS

Although there was no available physical or chemical information for butylated hydroxyanisole, it is a known antioxidant in fat-containing foods and in edible fats and oils. It is fat-soluble and would likely have a higher occurrence in organisms via a direct ingestion pathway than via any other pathway involving environmental media since it is primarily present in food.


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3) PESTICIDES

Pesticides can be divided into three categories based on half-life: non-persistent (half-life less than 30 days), moderately persistent (half-life from 30-100 days), and persistent (half-life greater than 100 days). With the exception of Atrazine, Carbaryl, Lindane, malathion, and pentachloronitrobenzene, the EDC pesticides have high bioconcentrations in the environment and tend to persist in both freshwater and saltwater for long periods of time.

With regards to lipophilicity, most pesticides have a log Kow greater than 5 and are therefore considered to be highly lipophilic. Therefore they tend to fall out of water solution and adsorb to particles or fat tissues of organisms. Half-lives are quite variable and range from very low to very high.

Specific physical and chemical properties of a subset of pesticides, known to be important in evaluating fate and transport, are presented below. A table of the associated with the physical and chemical properties for this EDC category follows.

ALDRIN

TERRESTRIAL FATE: Under most environmental conditions, Aldrin is gradually converted to Dieldrin. Aldrin is classified as moderately persistent meaning its half-life in soil ranged from 20-100 days.

AQUATIC FATE: Volatilization from water is also expected to be significant and will occur at a rate directly proportional to the rapidity of wind and current velocity and inversely proportional to the depth of the water body. Bioconcentration and adsorption to sediments are expected to be significant. Photooxidation is expected to be significant. Biodegradation is expected to be slow.

ATMOSPHERIC FATE: Direct photolysis is not expected to be significant.

CHLORDANE

TERRESTRIAL FATE: Chlordane released to soils may persist for long periods of time. Soil volatility studies have found that chlordane can volatilize significantly from soil surfaces on which it has been sprayed, particularly moist soil surfaces; however, shallow incorporation into soil was found to greatly restrict volatilization losses. Sufficient data are not available to predict the biodegradation rate of chlordane in soil. However, it has been suggested that chlordane is very slowly biotransformed in the environment (similar in nature to dieldrin).

AQUATIC FATE: Chlordane released to water is not expected to undergo significant hydrolysis, oxidation, or direct photolysis. Based on Henry's Law constant, chlordane can be expected to volatilize significantly from the water column to the atmosphere. The presence of chlordane in sediment core samples suggests that chlordane may be very persistent in the adsorbed state in the aquatic environment.

ATMOSPHERIC FATE: Pesticides applied to soils and crops may enter the atmosphere in several ways. Significant portions of aerially applied chemicals never reach the target and drift away from the treated area. Compounds may also volatilize from the treated areas and then contaminate the atmosphere. Long-distance transportation in the atmosphere may then take place in the vapor phase or the compound may be attached to airborne particles, eg, dust particles, water droplets and plant seeds.

DDT

TERRESTRIAL FATE: If DDT is released to soil it will adsorb very strongly to the soil and should not appreciably leach to groundwater. However, it has been detected in some groundwater samples. It will be subject to evaporation from soil surfaces. It will be subject to photooxidation on soil surfaces but will not hydrolyze. It may significantly biodegrade in flooded soils or under anaerobic conditions provided high populations of the required microorganisms are present.

AQUATIC FATE: There is ample evidence to demonstrate that DDT is very persistent in the environment. The dominant fate processes in aquatic environments are volatilization & sorption to biota & sediments, with the importance of sorption being determined by the amount of suspended particulate available in the water body. The ultimate transformation of DDT in the aquatic envrionment is probably by biotransformation. Photolysis of DDT in the gas phase has also been reported, but since DDT has been widely found throughout the biosphere, atmospheric transformations appear to be slow. There is also abundant evidence to demonstrate that bioaccumulation of DDT is a significant process in the environment. If DDT is released to water it will adsorb very strongly to sediments, significantly bioconcentrate in fish and will be subject to considerable evaporation. It may be subject to considerable indirect photodegradation near the surface of certain waters, but will not appreciably hydrolyze. It may be subject to biodegradation in waters and sediments where high populations of the required microorganisms are present, but generally biodegradation in water is poor. Direct photolysis of DDT in aqueous solution is very slow.

ATMOSPHERIC FATE: Under simulated atmospheric conditions, both DDT and DDE decompose to form carbon dioxide and hydrochloric acid. If released to air, DDT will be subject to direct photooxidation and reaction with photochemically produced hydroxyl radicals. The presence of DDT in samples far away from places where DDT is used suggests that photodegradation may be slow. Both wet and dry deposition are significant mechanisms of removal from the air.

HEPTACHLOR

TERRESTRIAL FATE: In soil, heptachlor will degrade to 1-hydroxychlordene, heptachlor epoxide and an unidentified metabolite less hydrophilic than heptachlor epoxide. Heptachlor is expected to adsorb strongly to soil and, therefore, resist leaching to groundwater. Volatilization from soil surfaces, especially wet ones, will be significant. Heptachlor incorporated into the soil will resist volatilization. Hydrolysis of heptachlor in moist soils is expected to be significant. Biodegradation may be important, especially under anaerobic conditions.

AQUATIC FATE: Chemical hydrolysis is expected to be the predominant fate of heptachlor in water. Bioconcentration in fish may also occur and volatilization of unadsorbed heptachlor may be significant. Due to its high Koc (1410000 l/kg), heptachlor is expected to adsorb to sediments. Biodegradation may also be significant, but is expected to occur relatively slowly compared to hydrolysis.

ATMOSPHERIC FATE: Based upon the vapor pressure (0.0004 Torr), heptachlor is expected to exist almost entirely in the vapor phase in ambient air . In the atmosphere, vapor phase reactions with photochemically produced hydroxyl radicals and ozone may be important fate processes. In addition, heptachlor may directly photolyze in the vapor phase. The low water solubility (0.18 mg/l) and the short atmospheric residence time of heptachlor indicates that physical removal from air by wet deposition (rainfall and dissolution in clouds, etc.) is of limited importance.

MALATHION

TERRESTRIAL FATE: If malathion is released to soil, it may moderately adsorb to the soil. Biodegradation may be an important fate process, especially in soils at < pH 7 where the rate of hydrolysis may be slow relative to the rate of biodegradation. Based on the range of Koc reported and the rapid degradation of malathion in soils, it should not leach to the groundwater.

AQUATIC FATE: If malathion is released to water it may moderately adsorb to sediment but will not be expected to bioconcentrate in aquatic organisms. Biodegradation may be an important process, especially in waters < pH 7.0 where the rate of hydrolysis may be slow relative to the rate of biodegradation. Volatilization from water should not be an important fate process.

ATMOSPHERIC FATE: If malathion is released to the atmosphere it may be subject to direct photolysis.

TOXAPHENE

TERRESTRIAL FATE: Toxaphene released to soils will persist for long periods of time. Biodegradation may be enhanced somewhat in flooded soils or under anaerobic conditions. Its low water solubility (0.74 mg/l) and strong adsorption to soil makes leaching into groundwater unlikely. It will be subject to loss by evaporation but will not hydrolyze or be removed significantly by runoff unless carried off adsorbed to clay particles.

AQUATIC FATE: Toxaphene released to water systems will not be likely to significantly hydrolyze, photolyze or significantly biodegrade. It will strongly adsorb to sediments and bioconcentrate in aquatic organisms. It will be subject to evaporation.

ATMOSPHERIC FATE: Toxaphene in the atmosphere is not readily degraded by direct photolysis. Toxaphene has been shown to be transported long distances in the air (1200 km).

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4) PHTHALATES

Phthalates are considered to be generally non-persistent to moderately persistent in the environment. If released to land, they will generally adsorb to soil and should not leach appreciably although they have been detected in groundwater. The most significant fate process for phthalates in soil will be biodegradation. Because of their low volatility, evaporation from soil is not expected to be significant. According to the log kow values, phthalates will be released to waters and will partition to solids such as sediment and biota.

Specific physical and chemical properties of a subset of phthalates, known to be important in evaluating fate and transport, are presented below. A table of the associated with the physical and chemical properties for this EDC category follows.

BUTYL BENZYL PHTHALATE

TERRESTRIAL FATE: When butyl benzyl phthalate (BBP) is released to land, it will adsorb to soil and should not leach appreciably although it has been detected in groundwater. The most significant fate process for BBP in soil will be biodegradation. Because of its low volatility, evaporation of BBP from soil is not expected to be significant.

AQUATIC FATE: Butyl benzyl phthalate has a log Kow of 4.8. Thus, BBP released to waters will partition to solids such as sediment and biota. The primary fate mechanism for BBP will be biodegradation. BBP has an estimated Henry's Law constant of <1.0X10-6 atm/mol m3; thus volatilization from water will not be significant except from shallow rivers or during high wind activity. Photodegradation and hydrolysis will not be significant. Bioaccumulation, biotransformation, and biodegradation are important aquatic fate processes for phthalate esters. Adsorption onto particulates and rainout are expected to be less important fate processes. The migration of phthalate esters out of plastics is slow. The amount available for transport or degradation is expected to be low. However, the formation of soluble complexes may increase their mobility.

ATMOSPHERIC FATE: Volatilization of BBP to the atmosphere is not expected to be a significant transport mechanism since its vapor pressure is only 8.3X10-6 Torr and its Henry's Law constant is <1.0X10-6 atm/mol m3.

DI-ETHYLHEXYL-PHTHALATE

TERRESTRIAL FATE: Di-ethylhexyl-phthalate (DEHP) released to soil will neither evaporate nor leach into groundwater. Limited data is available to suggest that it may biodegrade in soil under aerobic conditions following acclimation.

AQUATIC FATE: DEHP released to water systems will biodegrade fairly rapidly following a period of acclimation. It will also strongly adsorb to sediments and bioconcentrate in aquatic organisms. Evaporation and hydrolysis are not significant aquatic processes.

ATMOSPHERIC FATE: DEHP released to air will be carried for long distances in the troposphere and has been detected in air over the Atlantic and Pacific Oceans. Washout by rain appears to be a significant removal process. It is unknown whether direct photolysis or photooxidation are important atmospheric processes.


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5) METALS

Generally, metals tend to be insoluble and bioaccumulate in the environment. Specific physical and chemical properties of a subset of metals, known to be important in evaluating fate and transport, are presented below. A table of the associated with the physical and chemical properties for this EDC category follows.

ARSENIC

TERRESTRIAL FATE: Arsenic is naturally occurring in the environment and accounts for a small portion of the Earth’s crust minerals. Arsenic can undergo transformation (e.g., through redox ormicrobial processes). Arsenic can volatilize into the atmosphere as a result of different biological transformations. It can be adsorbed onto soil, washed away by surface runoff or leached into the groundwater, and be taken up by plants, subsequently entering into the food chain. In irrigated agricultural land, water lost by
evaporation will leave arsenic along with other minerals in the topsoil.

AQUATIC FATE: Arsenic is not water-soluble, but many of its compounds are water-soluble. Arsenic as a free element (0-oxidation state) is rarely encountered in natural waters. Soluble inorganic arsenate (+5-oxidation state) predominates under normal conditions since it is thermodynamically more stable in water than arsenite (+3 oxidation state). Fish generally contain lower concentrations of arsenic than other organisms indicating that it is not readily available for uptake in aquatic environments. In the irrigation field, it may undergo photo-oxidation in the presence of sunlight.

ATMOSPHERIC FATE: Arsenic and most of its compounds are solids that do not evaporate. They exist as small particles in the atmosphere. Burnt arsenic compounds exist as a gas. They will then settle into the soil or water depending upon where the air currents carry them. Arsenic does not break down, but does change form.

CADMUIM

TERRESTRIAL FATE: Cadmium is a naturally occurring element in the crust of the earth. Coal and other fossil fuels contain cadmium, and their combustion releases the element into the atmosphere. Cadmium is found naturally in various ores: lead and copper containing zinc, some iron ores, and sulfide ore. These can result in emissions to water. Volcanic emissions contain cadmium-enriched particles.

AQUATIC FATE: Some cadmium compounds are able to leach through soils into groundwater. When cadmium compounds bind to the sediments in water (rivers, lakes, bore water), they are less likely to be bioavailable.

ATMOSPHERIC FATE: Coal and oil burning power plants may emit cadmium compounds to air. Cadmium acts like other particles when in the atmosphere and is subject to deposition caused by rain or wind. The expected lifetime for particles in the atmosphere is about 5-15 days. Industrial emissions of cadmium and/or cadmium compounds can produce elevated, but still low-level, concentrations in the atmosphere around the source. Motor vehicles may also produce elevated levels of cadmium in areas of higher traffic. Tobacco smoke is the primary source of cadmium indoors.


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6) OTHER COMPOUNDS

Specific physical and chemical properties of the “OTHERS” EDC category are presented below. A table of the associated with the physical and chemical properties for this EDC category follows.

BENZO(A)PYRENE

TERRESTRIAL FATE: If benzo(a)pyrene is released to soil it will be expected to adsorb very strongly and will not be expected to leach to the groundwater; however, its presence in some groundwater samples indicates that it can be transported there by some mechanism. It will not hydrolyze, and evaporation from soils and surfaces is not expected to be significant. Based on the apparent lack of a significant competing fate process, biodegradation may be an important process in soils.

AQUATIC FATE: If released to water, benzo(a)pyrene (BaP) will be expected to adsorb very strongly to sediments and particulate matter. It will not hydrolyze but will be expected to bioconcentrate in aquatic organisms that are unable to metabolize it. It has been shown to be susceptible to significant metabolism by microorganisms in some natural waters without use as carbon or energy source, but in most waters and in sediments it has been shown to be stable towards biodegradation. BaP will be expected to undergo significant photodegradation near the surface of waters. Evaporation may be significant. Adsorption to sediments and particulates may significantly retard biodegradation, photodegradation, and evaporation.

ATMOSPHERIC FATE: Benzo(a)pyrene (BaP) released to the atmosphere will likely be associated with particulate matter and may be subject to moderately long transport, depending mainly on the particle size distribution and climactic conditions which will determine the rates of wet and dry deposition. Its presence in areas remote from primary sources demonstrates the potential for long-range transport as well as BaP's considerable stability in the air. It may be subject to direct photodegradation.

RESORCINOL

TERRESTRIAL FATE: The major degradation process for resorcinol in soil is expected to be biodegradation. A number of biological screening studies have found resorcinol to be readily biodegradable. Resorcinol is expected to leach readily in soil; however, leaching may not be important if concurrent biodegradation occurs at a rapid rate.

AQUATIC FATE: The major degradation processes for resorcinol in natural water may be biodegradation and photooxidation. A number of biological screening studies have found resorcinol to be readily biodegradable. By analogy to other phenol compounds, resorcinol may react relatively rapidly in sunlit natural water with photochemically produced oxidants such as hydroxyl and peroxy radicals. Aquatic hydrolysis, volatilization, adsorption to sediments, and bioconcentration are not expected to be important.

ATMOSPHERIC FATE: Based upon a vapor pressure of 0.00045 Torr, resorcinol can be expected to exist almost entirely in the gas-phase in the ambient atmosphere. Gas-phase resorcinol is expected to degrade rapidly in air by reaction with photochemically produced hydroxyl radicals. Night-time reaction with nitrate radicals may also contribute to the atmospheric transformation of resorcinol.


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