Bioaccumulation is the gradual accumulation of substances, such as pesticides or other chemicals, in an organism. Bioaccumulation occurs when an organism absorbs a substance faster than it can be lost or eliminated by catabolism and excretion. Thus, the longer the biological half-life of a toxic substance, the greater the risk of chronic poisoning, even if environmental levels of the toxin are not very high. Bioaccumulation, for example in fish, can be predicted by models. Hypothesis for molecular size cutoff criteria for use as bioaccumulation potential indicators are not supported by data. Biotransformation can strongly modify bioaccumulation of chemicals in an organism.
Aquatic toxicology is the study of the effects of manufactured chemicals and other anthropogenic and natural materials and activities on aquatic organisms at various levels of organization, from subcellular through individual organisms to communities and ecosystems. Aquatic toxicology is a multidisciplinary field which integrates toxicology, aquatic ecology and aquatic chemistry.
Methylmercury (sometimes methyl mercury) is an organometallic cation with the formula [CH3Hg]+. It is the simplest organomercury compound. Methylmercury is extremely toxic, and its derivatives are the major source of organic mercury for humans. It is a bioaccumulative environmental toxicant with a 50-day half-life. Methylmercury is the causative agent of the infamous Minamata disease.
Persistent organic pollutants (POPs) are organic compounds that are resistant to degradation through chemical, biological, and photolytic processes. They are toxic and adversely affect human health and the environment around the world. Because they can be transported by wind and water, most POPs generated in one country can and do affect people and wildlife far from where they are used and released.
Dieldrin is an organochlorine compound originally produced in 1948 by J. Hyman & Co, Denver, as an insecticide. Dieldrin is closely related to aldrin, which reacts further to form dieldrin. Aldrin is not toxic to insects; it is oxidized in the insect to form dieldrin which is the active compound. Both dieldrin and aldrin are named after the Diels-Alder reaction which is used to form aldrin from a mixture of norbornadiene and hexachlorocyclopentadiene.
Toxaphene was an insecticide used primarily for cotton in the southern United States during the late 1960s and the 1970s. Toxaphene is a mixture of over 670 different chemicals and is produced by reacting chlorine gas with camphene. It can be most commonly found as a yellow to amber waxy solid.
Dichlorodiphenyldichloroethylene (DDE) is a chemical compound formed by the loss of hydrogen chloride (dehydrohalogenation) from DDT, of which it is one of the more common breakdown products. Due to DDT's massive prevalence in society and agriculture during the mid 20th century, DDT and DDE are still widely seen in animal tissue samples. DDE is particularly dangerous because it is fat-soluble like other organochlorines; thus, it is rarely excreted from the body, and concentrations tend to increase throughout life. The major exception is the excretion of DDE in breast milk, which transfers a substantial portion of the mother's DDE burden to the young animal or child. Along with accumulation over an organism's lifetime, this stability leads to bioaccumulation in the environment, which amplifies DDE's negative effects.
Soil contamination, soil pollution, or land pollution as a part of land degradation is caused by the presence of xenobiotic (human-made) chemicals or other alteration in the natural soil environment. It is typically caused by industrial activity, agricultural chemicals or improper disposal of waste. The most common chemicals involved are petroleum hydrocarbons, polynuclear aromatic hydrocarbons, solvents, pesticides, lead, and other heavy metals. Contamination is correlated with the degree of industrialization and intensity of chemical substance. The concern over soil contamination stems primarily from health risks, from direct contact with the contaminated soil, vapour from the contaminants, or from secondary contamination of water supplies within and underlying the soil. Mapping of contaminated soil sites and the resulting clean ups are time-consuming and expensive tasks, and require expertise in geology, hydrology, chemistry, computer modelling, and GIS in Environmental Contamination, as well as an appreciation of the history of industrial chemistry.
The Guadalupe River watershed consists of 170 square miles (400 km2) of land within northern California's Santa Clara County. The surface runoff from this area drains into the Guadalupe River, its tributary streams, reservoirs or other bodies of water which all eventually gets carried into the San Francisco Bay. Essentially, all the water from the creeks and rivers that make up the Guadalupe watershed, including water from storm drains, flows into the Guadalupe River, and then flows downstream into the San Francisco Bay at the Alviso Slough in Alviso. The Guadalupe watershed's main tributaries include Los Gatos Creek, Trout Creek, Hendrys Creek, Ross Creek, Pheasant Creek, Rincon Creek, Herbert Creek, and Golf Creek. Six major reservoirs exist in the watershed: Calero Reservoir on Arroyo Calero, Guadalupe Reservoir on Guadalupe Creek, Almaden Reservoir on Los Alamitos Creek, Vasona Reservoir, Lexington Reservoir, and Lake Elsman on Los Gatos Creek.
Environmental toxicology is a multidisciplinary field of science concerned with the study of the harmful effects of various chemical, biological and physical agents on living organisms. Ecotoxicology is a subdiscipline of environmental toxicology concerned with studying the harmful effects of toxicants at the population and ecosystem levels.
The presence of mercury in fish is a health concern for people who eat them, especially for women who are or may become pregnant, nursing mothers, and young children. Fish and shellfish concentrate mercury in their bodies, often in the form of methylmercury, a highly toxic organomercury compound. This element is known to bioaccumulate in humans, so bioaccumulation in seafood carries over into human populations, where it can result in mercury poisoning. Mercury is dangerous to both natural ecosystems and humans because it is a metal known to be highly toxic, especially due to its neurotoxic ability to damage the central nervous system.
Biodilution, sometimes referred to as bloom dilution, is the decrease in concentration of an element or pollutant with an increase in trophic level. This effect is primarily observed during algal blooms whereby an increase in algal biomass reduces the concentration of pollutants in organisms higher up in the food chain, like zooplankton or daphnia.
Mercury regulation in the United States limit the maximum concentrations of mercury (Hg) that is permitted in air, water, soil, food and drugs. The regulations are promulgated by agencies such as the Environmental Protection Agency (EPA) and Food and Drug Administration (FDA), as well as a variety of state and local authorities. EPA published the Mercury and Air Toxics Standards (MATS) regulation in 2012; the first federal standards requiring power plants to limit emissions of mercury and other toxic gases.
In aquatic toxicology, bioconcentration is the accumulation of a water-borne chemical substance in an organism exposed to the water.
Persistent, bioaccumulative and toxic substances (PBTs) are a class of compounds that have high resistance to degradation from abiotic and biotic factors, high mobility in the environment and high toxicity. Because of these factors PBTs have been observed to have a high order of bioaccumulation and biomagnification, very long retention times in various media, and widespread distribution across the globe. Most PBTs in the environment are either created through industry or are unintentional byproducts.
Tissue residue is the concentration of a chemical or compound in an organism's tissue or in a portion of an organism's tissue. Tissue residue is used in aquatic toxicology to help determine the fate of chemicals in aquatic systems, bioaccumulation of a substance, or bioavailability of a substance, account for multiple routes of exposure, and address an organism's exposure to chemical mixtures. A tissue residue approach to toxicity testing is considered a more direct and less variable measure of chemical exposure and is less dependent on external environmental factors than measuring the concentration of a chemical in the exposure media.
Drug pollution or pharmaceutical pollution is pollution of the environment with pharmaceutical drugs and their metabolites, which reach the aquatic environment through wastewater. Drug pollution is therefore mainly a form of water pollution.
Energy, nutrients, and contaminants derived from aquatic ecosystems and transferred to terrestrial ecosystems are termed aquatic-terrestrial subsidies or, more simply, aquatic subsidies. Common examples of aquatic subsidies include organisms that move across habitat boundaries and deposit their nutrients as they decompose in terrestrial habitats or are consumed by terrestrial predators, such as spiders, lizards, birds, and bats. Aquatic insects that develop within streams and lakes before emerging as winged adults and moving to terrestrial habitats contribute to aquatic subsidies. Fish removed from aquatic ecosystems by terrestrial predators are another important example. Conversely, the flow of energy and nutrients from terrestrial ecosystems to aquatic ecosystems are considered terrestrial subsidies; both aquatic subsidies and terrestrial subsidies are types of cross-boundary subsidies. Energy and nutrients are derived from outside the ecosystem where they are ultimately consumed.
Mercury contamination in California waterways poses a threat to both the environment and human health. This naturally occurring heavy metal may be released into the environment from natural geological sources, but most commonly occurs from anthropogenic mining operations. This metal poses a threat not only for its effects on organisms, but also for difficulty of removal from waterways and the trouble in efficiently detecting it. The roots of mercury poisoning in waterways began with the historic mining of gold within California's streambed and hillsides; since the California Gold Rush, mercury has been used for gold extraction for its ability as a catalyze with the precious metal. due to the process of extraction and washing, mercury used would either be burned away as a hazardous vapor, or washed away into waterflows, resulting in widespread contamination of river and lake sediments. mercury continues to be released today through anthropogenic sources, though state and federal agencies work to manage and ban these practices and to mitigate its effect on the environmental and on people. Many water bodies in the state of California bear fish consumption advisories due to mercury content.
Mercury is a poisonous element found in various forms in Canada. It can be emitted in the atmosphere naturally and anthropogenically, the main cause of mercury emission in the environment. Mercury pollution has become a sensitive issue in Canada for the past few decades and many steps have been taken for prevention at local, national, and international levels. It has been found to have various negative health and environmental effects. Methylmercury is the most toxic form of mercury which is easily accessible as well as digestible by living organisms and it is this form of mercury causing serious harm to human and wildlife health.
