Toxic chemicals mixtures

For those users who want a more detailed presentation on the synthetic chemicals in our food as well as exposure to toxic chemical mixtures across the nation, a complete presentation is given in our upcoming book Toxic Legacy. Synthetic Toxins in the Food. Water and Air of American Cities which will be available in 2006. 

Xenobiotics can serve to induce or inhibit enzymes that are metaboli-cally important. This effect is particularly important when considering the effects of toxic chemical mixtures. Chemicals that are nontoxic or mildly toxic can serve to potentiate or synergize the toxicity of other compounds by inducing or inhibiting the detoxifying enzymes. 

Some of the effects of toxic chemical mixtures on soil pollution are predictable. Acidic soils dissolve otherwise insoluble metal oxides and salts, thereby increasing available metal concentrations and toxicity to flora and fauna. Available copper content is inversely proportional to increased pH of soiU4 Earthworm mortality in soil polluted by lead increases as pH decreases. I15l The addition of ethylenediaminetetraacetic acid (EDTA) and its disodium salt to soil contaminated with cadmium, lead, and zinc increases the availability of these metals to plants and results in significant increases in the uptake of these in plants. I25l... 

Other effects of toxic chemical mixtures on soil are not predictable. Mixtures of fertilizers and pesticides produce enhanced toxic effects. The additions of urea, superphosphate, and potash enhance the toxicities of carbaryl and carbofuran insecticides to nitrogen-fixing bacteria in soilJ26 Soil co-contaminated with arsenic and DDT does not break down DDT as rapidly as soil contaminated with DDT alone. This results in a persistence of DDT in the environment. I27 ... 

Adverse reactions to foods are not always attributable to any one food or even a mixture of ingredients in foods. Individuals can react to mixtures of xenobiotic chemicals arising from more than one food. Chemical A can be present in one food, whereas chemicals B or C or D, and so on, can come from other foods, with the mixture (s) forming after ingestion of combinations of foods. Toxic chemical mixtures can also arise from a combination of food ingestion and environmental exposure (s) to different molecular species. 

The following sections describe case studies for which the effects of single chemicals have been ruled out. These studies represent only a fraction of those demonstrating the known effects of toxic mixture exposure. They are meant to illustrate the scope of hazards faced when humans are exposed to toxic chemical mixtures. 

Our discussion here is dedicated to the unexpected effects of toxic chemical mixtures. For information on identified or suspected single hepatotoxic chemicals, it is suggested that the reader carry out a literature search for the specific species of interest. 

With the passage of time, many previously unexplained diseases and injuries have been related to toxic chemical mixture exposures. These include CNS, respiratory system, immune system, carcinogenic, and other endpoints. I19l Further such discoveries are to be anticipated. 

Part IV is devoted to regulatory requirements for toxic chemical warnings for chemicals and chemical products and the need to adjust recommended exposure levels for products containing chemical mixtures. This part also contains suggestions for limiting mixture exposures in the products we use and recommendations for limiting environmental exposures to toxic chemical mixtures. 

Some of the effects of toxic chemical mixtures on soil pollution are predictable. Acidic soils dissolve otherwise insoluble metal oxides and salts, thereby increasing available metal concentrations and toxicity to flora and fauna. Available copper content is... 

Most of the chemicals listed in Table 11.2 target the respiratory and central nervous systems. Exposures in arts and crafts use are almost always to mixtures of lipophilic and hydrophilic chemicals. When used in areas with poor air circulation (as is often the case in home use) unexpected acute toxicity can result [3]. For example, it has been reported that exposure to formaldehyde and terpene hydrocarbons at very low levels unexpectedly produced dyspnea and other lower lung symptoms in woodworkers. The effects could not be attributed to either formaldehyde or terpenes alone at low levels of exposure [4]. In another example, it was reported that chronic exposure to a combination of very low concentrations of MEK, ethyl acetate, and aliphatic hydrocarbons in a leather-adhesive formulation induced unanticipated CNS effects [5]. Some products that are considered by most to be benign contain toxic chemical mixtures. Marker pens contain mixtures of methanol, ethanol, propanols, butanols, butyl acetate, and MIBK. Though such markers are labeled as nontoxic, ... 

The scientific community almost unanimously agrees that global warming is accompanied by changes in the frequency and intensity of extreme climatic events such as intense hurricanes, tornadoes, and flooding from more frequent and intense rainfall [22-24], These events almost always result in the release of large quantities of toxic chemical mixtures of unpredictable composition. The following sections demonstrate this phenomenon. 

On May 25, 2008, a severe tornado hit Parkersburg, New Hartford, and Dunkerton, Iowa. Drums of toxic waste were dispersed by the tornado, and three Superfund toxic waste sites were impacted, resulting in the release of toxic chemical mixtures [29]. 

Severe flooding following rainstorms is increasing in many geographical areas due to global warming. In the United States, such flooding has impacted Superfund sites and resulted in the release of toxic chemical mixtures. Two such areas, one in Idaho and the other in Arkansas, are illustrative of this phenomenon. 

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