Toxic chemicals sensitizers

CH rCHCH NHCSNH. Colourless crystalline solid with a faint garlic-like odour m.p. 74 C. Manufactured by treating propenyl isothiocyanate with a solution of ammonia in alcohol. It has been given by injection in the treatment of conditions associated with the formation of excessive fibrous tissue. Toxic side reactions may occur. Propenyl thiourea is a chemical sensitizer for photographic silver halide emulsions. 

MCS may result from a single massive exposure to one or more toxic substances or repeated exposure to low doses. On one hand, some people may become chemically sensitive following a toxic chemical spill at work or in their community or after being sprayed directly with pesticides. On the other, individuals may develop this condition from spending forty hours each week in a poorly ventilated building where they breathe a profusion of chemicals common to our modem way of life. 

In nonindustrial settings, MCS substances are the cause of indoor air pollution and are the contaminants in air and water. Many of the chemicals which trigger MCS symptoms are known to be irritants or toxic to the nervous system. As an example, volatile organic compounds readily evaporate into the air at room temperature. Permitted airborne levels of such contaminants can still make ordinary people sick. When the human body is assaulted with levels of toxic chemicals that it cannot safely process, it is likely that at some point an individual will become ill. For some, the outcome could be cancer or reproductive damage. Others may become hypersensitive to these chemicals or develop other chronic disorders, while some people may not experience any noticeable health effects. Even where high levels of exposure occur, generally only a small percentage of people become chemically sensitive. 

When an airborne toxic chemical is introduced into a plant conmiunity, some plants will be more affected than others depending on individual tolerances endowed by their genotype, as well as on their phenology, and various modifying microclimatic variables. The sensitive plants or species that are no longer able to compete adequately with the tolerant plants or species will be partially or completely replaced. Some scientists propose that the widespread... 

The multimedia model present in the 2 FUN tool was developed based on an extensive comparison and evaluation of some of the previously discussed multimedia models, such as CalTOX, Simplebox, XtraFOOD, etc. The multimedia model comprises several environmental modules, i.e. air, fresh water, soil/ground water, several crops and animal (cow and milk). It is used to simulate chemical distribution in the environmental modules, taking into account the manifold links between them. The PBPK models were developed to simulate the body burden of toxic chemicals throughout the entire human lifespan, integrating the evolution of the physiology and anatomy from childhood to advanced age. That model is based on a detailed description of the body anatomy and includes a substantial number of tissue compartments to enable detailed analysis of toxicokinetics for diverse chemicals that induce multiple effects in different target tissues. The key input parameters used in both models were given in the form of probability density function (PDF) to allow for the exhaustive probabilistic analysis and sensitivity analysis in terms of simulation outcomes [71]. 

This section demonstrates that (1) free ionic copper (Cu2+) is the most toxic chemical species of copper and that copper bioavailability is modified by many biological and abiotic variables (2) copper metabolism and sensitivity to copper of poikilotherms differs from that of mammals and (3) copper interactions with inorganic and organic chemicals are substantial and must be considered when evaluating copper hazards to natural resources. 

We re all kind of entwined in this evolution that we re going through. The whole planet is out of balance right now, and we who have chemical sensitivities are suffering the consequences of that. And I don t think it s just those of us with chemical sensitivities, it s people with cancer and other illnesses created by our toxic environment. 

Scientists acknowledge that many substances contain chemicals known to be toxic in high concentrations. To chemically sensitive people, these and other substances can be harmful even in minute amounts. A whiff of hair spray, fresh paint or bug spray, for example, can be debilitating to a person with multiple chemical sensitivities. People with MCS must avoid chemical exposures or symptoms will persist or worsen and the illness will progress. 

While many of the symptoms reported by people with MCS are similar to known toxic reactions, they usually occur at exposure levels previously thought to be safe. Additionally, many chemically sensitive people experience symptoms vastly different from typical toxic reactions. 

The c-phthalaldehyde reaction compares favourably with the ninhydrin reaction in several respects. The reagent is stable and is in an aqueous form, which eliminates the use of potentially toxic chemicals and storage under nitrogen. Because the reaction proceeds quickly at room temperature there is no need for the 100°C heating bath with all its inherent problems, and the increased sensitivity permits detection at the picomole level. 

Ideally, a full data set should be available for the hazard assessment of a chemical substance, including animal tests to evaluate the toxicokinetics and the following toxicological properties acute toxicity, irritation, sensitization, toxicity following repeated exposure to the substance, mutagenicity and genotoxicify, carcinogenicity, and effects on fertility and fetal development. 

Although chemical sensitization is a more complex process than immunosuppression, by far most of the efforts on developing in vitro assays are in this field. An important reason for this is that from the various fields of immunotoxicity, most of the animals are used for sensitization testing. In fact the number of animals required for sensitization is second only after developmental toxicity testing. 

There is further analogy with yet "extra concern for toxic chemicals that may also persist in the environment and be transported great distances from their point of entry into the environment. Here the unifying general notion is that unsuspecting individuals are placed at risk, and are thus less able to defend than are the perpetrators. Mercury is a classic example of such a chemical. Mercury is extremely toxic to the CN S. Fetuses, infants, and toddlers are especially sensitive and susceptible to the neurotoxic properties of mercury. Mercury also persists in the environment, and is known to bioaccumulate in the food web and biomagnify up the food chain. 

The surest way to inhibit an enzyme is to block the active site irreversibly by chemical reaction with some active species to form a covalent bond. Thus, iodoacetate will irreversibly inactivate thiol proteases by forming the stable carboxymethyl mercaptan. lodoacetate is of course non-selective (many other enzymes would be inactivated), toxic (many sensitive sites would be alkylated) and moreover the drug itself is unstable due to its very reactivity. 

Simple trialkylphosphines, R3P, can be prepared relatively easily by using excess Grignard or alkyllithium reagents.1,2 However, the synthesis of mixed R2 R P monophosphines or chelating aliphatic ligands of the type of R2 P(CH2 )n A (where A = a donor group and n - 2,3,4) have been almost prohibitively difficult, owing to the toxicity, chemical reactivity, oxidation sensitivity, and commercial unavailability of likely precursors. 

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