Exposure and Environmental Fate

Data on exposure and environmental fate are needed, not to determine toxicity, but to provide information that may be useful in the prediction of possible exposure in the event that the chemical is toxic. These tests are primarily useful for chemicals released into the environment such as pesticides, and they include the rate of breakdown under aerobic and anaerobic conditions in soils of various types, the rates of leaching into surface water from soils of various types, and the rate of movement toward groundwater. The effects of physical factors on degradation through photolysis and hydrolysis studies and the identification of the product formed can indicate the rate of loss of the hazardous chemical or the possible formation of hazardous degradation products. Tests for accumulation in plants and animals and movement within the ecosystem are considered in Section 21.7. 

---

Faroon O, Kueberuwa S, Smith L, and DeRosa C (1995) ATSDR evaluation of health effects of chemicals. II. Mirex and chlordecone Health effects, toxicokinetics, human exposure, and environmental fate. Toxicology and Industrial Health 11(6) 1-203. 

General Properties, Uses, Human Exposures and Environmental Fate... 

In this step, the assessor qiuuitifies tlie magnitude, frequency and duration of exposure for each patliway identified in Step 2. Tliis step is most often conducted in two stages estimation of exposure concentrations and calculation of intakes. The later estimation is considered in Step 4. In tliis part of step 3. the exposure assessor determines the concentration of chemicals tliat will be contacted over the exposure period. E.xposure concentrations are estimated using monitoring data and/or chemical transport and environmental fate models. Modeling may be used to estimate future chemical concentrations in media tliat are currently contaminated or tliat may become contaminated, and current concentrations in media and/or at locations for which tliere are no monitoring data. The bulk of the material in tliis chapter is concerned witli tliis step. 

An exposure and risk assessment will usually integrate a number of different inputs, including health and environmental effects evaluations as well as pollutant profiles for environmental releases, ambient monitoring data, and environmental fate... 

Cripe, G.M., D J. Hansen, S.F. Macauley, and J. Forester. 1986. Effects of diet quantity on sheepshead minnows (Cyprinodon variegatus) during early fife-stage exposures to chlorpyrifos. Pages 450-46 in T.M. Poston and R. Purdy (eds.). Aquatic toxicology and environmental fate ninth symposium. ASTM Spec. Tech. Publ. 921, American Society for Testing and Materials, Philadelphia, PA. 

Exposure Levels in Environmental Media. There were no quantitative data on current atmospheric levels of 3,3 -dichlorobenzidine emissions or on the chemical s potential to act as a surface eontaminant of soil environments. It is difficult to determine 3,3 -dichlorobenzidine levels in the aquatic environment because the concentrations tend to be at or below analytical detection limits. In general, it may only be possible to ascertain fully the environmental fate of 3,3 -dichlorobenzidine as analytical advances permit the routine determination of very low concentrations. Moreover, determination of the nature and environmental fate of breakdown products of 3,3 -dichlorobenzidine would be useful. 

ERA ERI Suite, physical/chemical property and environmental fate estimation models. http //www.epa.gov/oppt/exposure/docs/episuite/htm. 

Through functional-use analysis, toxicological and environmental fate data on structurally similar chemicals can be applied to each member of a functional-use class. A focus on functional use not only offers commonality in perspective for chemical innovators, but also simplifies the risk assessment process. Within a given product dass, the use and exposure patterns are generally the same, with minor variability therefore, the hazard component of the risk equation becomes a... 

The assessment which is undertaken by NICNAS covers the assessment of the health and aquatic toxicity hazards of the chemical, occupational exposure, public exposure and environmental exposure and fate. A risk assessment is performed and recommendations are made to control and minimise the risks. The results of the assessment are published in a report which is made available to the public via the NICNAS Web site [3]. 

As defined previously, risk is a function of hazard and exposure. In the environmental risk context, hazard is a function of toxicity which is affected by physical/chemical and environmental fate properties and hence chemistry. Green chemistry reduces the risk or environmental impact of processes or products by focusing on the hazard component. 

Chemical data (e.g., physical and chemical properties, structureactivity relationships, and environmental fate and transport), basic toxicity data, and pharmacokinetic data (information on absorption, distribution (including placental and lactational transfer), metabolism, and excretion) should be reviewed. These data are particularly important because reproductive and developmental effects are interpreted in the context of general toxicity data in humans or experimental animals. Pharmacokinetic data for both animals and humans can be helpful in extrapolating exposure levels from one species to another. 

Saxitoxin is a naturally occurring substance in dino-flagellates and taken up by shellfish. Consumption of the shellfish leads to toxicity. Aside from the knowledge that these organisms serve as a source of exposure, the environmental fate of the chemical... 

Parker RD, Rieder DD. The generic expected environmental concentration program, ENEEC. Part B. Users Manual Tier one screening model for aquatic pesticide exposure. Washington Environmental Fate and Effects Division, Office of Pesticide Programs, US Environmental Protection Agency, 1995. 

The experienced Judgment must integrate chemical and physical properties, use/exposure potential, toxicity and environmental fate information in order to target the risk assessment process toward real risks Instead of trivial risks. 

If data has already been submitted to the EPA without any claims of confidentiality, it does not need to be included with the PMN and instead the PMN submitter can identify the recipient by name or office, the date of the prior submission, and any standard literature citation to the reportd Data on exposure pathways outside of the United States does not need to be submitted with a PMN, but all data on health, environmental effects, physical and chemical properties, and environmental fate must be reported no matter where the data was generated. 

The toxicity profile of the biocide is very important. Biocides that can be leached out of the plastic or bloom to the surface are an exposure risk to humans and the environment. Fish toxicity is also very important in pond and ditch liner applications. The environmental fate of the biocide must also be considered. It is desirable that the biocide is biodegradable and not persistent in the environment after it is done protecting the plastic. Extensive supporting documentation is required on the toxicity and environmental fate of any new product. 

P. H. Howard, ed.. Handbook of Environmental Fate andExposure Datafor Organic Chemicals, Vol. Ill, Pesticides, Lewis PubHshers, Chelsea, Mich., 1991. Provides chemical and physical properties of 70 pesticide active ingredients reviews data on environmental fate and exposure potential, with general references. 

As most organotins decompose, boiling points of 250 °C were assumed in the absence of a "true boiling point. The values for Henry s law constant and organic carbon/water partition coefficient were all derived from EUSES unless otherwise indicated. The chlorides were chosen as soluble salts in this table toxicity is independent of salt (see section 8), and soluble salts maximize likely environmental exposure, giving worst case in modelling environmental fate. 

---