Ecological effects field

As explained in Section 5.2.3, p,p -DDE is much more persistent in food chains than either p,p -DDT or p,p -DDD, and dnring the 1960s when DDT was still extensively used, it was often the most abundant of the three compounds in birds and mammals found or sampled in the field. Since the widespread banning of DDT, very little of the pesticides has been released into the environment, and p,p -DDE is by far the most abnndant DDT residue found in biota. While discussing the ecological effects of DDT and related compounds, effects on population numbers will be considered before those on popnlation genetics (gene frequencies). 

PCDDs and PCDEs, together with coplanar PCBs, can express Ah-receptor-mediated toxicity. TCDD (dioxin) is used as a reference compound in the determination of TEFs, which can be used to estimate TEQs (toxic equivalents) for residues of PHAHs found in wildlife samples. Biomarker assays for Ah-receptor-mediated toxicity have been based on the induction of P450 lAl. TEQs measured in field samples have sometimes been related to toxic effects upon individuals and associated ecological effects (e.g., reproductive success). 

One of the leaders in the field, Carl Erik Nord, stated that ecological effects are difficult to predict and clinical studies of new antibiotics should include investigations of... 

Tolle, D. A., Arthur, M. F. Van Voris, P. 1983. Microcosm/field comparison of trace element uptake in crops grown in fly ash-amended soil. Ecological effects of soil amended with waste products. Science of the Total Environment, 31, 243-261. 

De Zwart D. 2005. Ecological effects of pesticide use in the Netherlands modeled and observed effects in the field ditch. Int Environ Assess Manag 1 123-134. 

TRIAD approach Integrated approach to determine ecological effects of pollution by a complex mixture, applying a combination of chemical analysis, bioassays, and ecological field observations. 

Sources of data that might be used in the construction of stressor-response functions include the results of toxicity tests (lethal, chronic) performed under controlled laboratory conditions, direct measures of exposure and response in controlled field experiments, and the application of statistical relationships that estimate the biological effects of chemicals based on physical or chemical properties of specific toxicants. The order of preference among these sources of data lists field observations as the most valuable, followed by laboratory toxicity tests, and finally by the use of empirical relationships. In the absence of directly relevant data, the development of stressor-response functions may require the use of extrapolations among similar stressors or ecological effects for which data are available. For example, effects might have to be extrapolated from the available test species to an untested species of concern in an ERA. Similarly, toxicity data might be available only for a chemical similar to the specific chemical stressor of concern in an ERA, and thereby require an extrapolation from one chemical to another to perform the assessment. 

Chapter 2, A Framework for Environmental Toxicology, provides an overview of the field of environmental toxicology and introduces the progression from the initial introduction of the toxicant to the environment, its effect upon the site of action, and finally the impacts upon an ecosystem. Many of the terms used throughout this book are introduced in this section. After an introduction to toxicity testing, the remainder of the book is organized from the molecular chemistry of receptors to the ecological effects seen at the system level. 

Methods and measurements used in biomonitoring for ecological effects. A number of methods are used both in a laboratory situation and in the field to attempt to classify the effects of xeno-biotics upon ecological systems. Toxicity tests can be used to examine effects at several levels of biological organization and can be performed with species introduced as monitors for a particular environment. 

Ecological effects data may come from a variety of sources. Relevant sources of information include field observations (e.g., fish or bird kills, changes in aquatic community structure), field tests (e.g., microcosm or mesocosm tests), laboratory tests (e.g., single species or microcosm tests), and chemical structure-activity relationships. Available information on ecological effects can help focus the assessment on specific stressors and on ecological components that should be evaluated. 

Many factors can influence the utility of available ecological effects data for problem formulation. For example, the applicability of laboratory-based tests may be affected by any extrapolations required to specific field situations, while the interpretation of field observations may be influenced by factors such as natural variability or the possible presence of stressors other than the ones that are the primary focus of the risk assessment... 

Data from both field observations and experiments in controlled settings can be used to evaluate ecological effects. In some cases, such as for chemicals that have yet to be manufactured, test data for the specific stressor are not available. Quantitative structure-activity relationships (QSARs) are useful in these situations (Auer et al. 1990, Clements et al. 1988, McKim et al. 1987). 

The results of the characterization of ecological effects are summarized in a stressor-response profile that describes the stressor-response relationship, any extrapolations and additional analyses conducted, and evidence of causality (e.g., field effects data). 

Evidence of causality. The degree of correlation between the presence of a stressor and some adverse effect is an important consideration for many ecological risk assessments. This correlation is particularly true when an assessor is attempting to establish a link between certain observed field effects and the cause of those effects. Further discussions of the evaluation of causal relationships may be found in the section on characterization of ecological effects (Section 3.2.2). 

One of the first steps in the risk assessment process involves the collection of available information on the physicochemical properties, ecological effects, environmental fate, and health effects for a given chemical. In a nontesting strategy, data are also essential to make predictions by means of the read-across approach. Data can be retrieved from books, Internet-based resources (free and commercial resources), or commercial databases. This is a vast and rapidly developing field, so the reader is referred elsewhere for discussions of data sources [28-31],... 

Ecological effects assessment literature reviews, field studies and toxicity tests linking contaminant concentrations to effects on ecological receptors (USEPA, 1989c). 

In ecological effects assessment, there are many problems involved, eg, it is often observed that laboratory test data over estimate more commonly than underestimate toxicity, because laboratory toxicity tests are conducted in filtered water of low suspended solids eg, soil particles) and low organic matter content, which play an important role in natural environments. Therefore, test methods including multi-species and simulating environmental conditions, ie, more sophisticated ecosystems or field test methods should be developed for determination of more reliable assessment factors (AFs), in spite of its difficulties. It will be necessary to develop both aquatic toxicology methods and terrestrial or sediment ecotoxicology. 

US EPA (1996). Field testing for poUinators (OPPTS 850.3040) Ecological effects test guidehnes. EPA 712-C-96-150. Washington DC, USA. 

The SEHSC research efforts combined with those by the GSC resulted in the development of a comprehensive environmental database for PDMS, a material that has both industrial and consumer product applications. The results of this five-year research effort demonstrated that most PDMS used in down-the-drain applications enters the terrestrial environment as a component of wastewater treatment plant sludge, with aquatic sediments receiving between 3 to 6 % of this mass. Laboratory and field studies demonstrated the potential for PDMS degradation in soils and sediments. The rate of degradation is slow in sediment and wet soil and increases as a function of decreased moisture level to half-life values of days in dry soil. No adverse ecological effects are indicated from the effects testing. 

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