Chemical toxic

Chemicals may be encountered as reactants, solvents, catalysts, inhibitors, as starting materials, finished products, by-products, contaminants, or off-specification products. They may vary from pure, single substances to complex proprietary formulations. 

Exposures to chemicals may involve solids, liquids, or airborne matter as mists, aerosols, dusts, fumes (i.e. pm-sized particulates), vapours or gases in any combination. Many situations, e.g. exposure to welding fumes or to combustion products from fossil fuels, include mixtures both of chemicals and of physical forms. Quantification of exposure is then difficult. 

An exposure to a specific chemical in relatively low concentrations over a period may result in chronic effects. At higher concentrations, the effects may be acute. Some chemicals produce local damage at their point of contact with, or entry into, the body others produce systemic effects, i.e. they are transported within the body to various organs before exerting an adverse effect. 

The toxicity of a substance is its capacity to cause injury once inside the body. The main modes of entry into the body by chemicals in industry are inhalation, ingestion and absorption through the skin. Gases, vapours, mists, dusts, fumes and aerosols can be inhaled and they can also affect the skin, eyes and mucous membranes. Ingestion is rare though possible as a result of poor personal hygiene, subconscious hand-to-mouth contact, or accidents. The skin can be affected directly by contact with the chemicals, even when intact, but its permeability to certain substances also offers a route into the body. Chemicals accorded a skin notation in the list of occupational exposure limits (see Table 4.34) are listed in Table 4.2. 

Have a corrosive or a vesicant (biistering) effect on moist or mucous surfaces. 

Concentration may be more important than duration of exposure. Animals and man react similarly. 

The oil and gas service companies used hydraulic fracturing products containing 29 chemicals that are (1) known or possible human carcinogens, (2) regulated under the Safe Drinking Water Act for their risks to human health, or (3) listed as hazardous air pollutants (HAPs) under the Qean Air Act. These 29 chemicals were components of 652 different products used in hydraulic fracturing. Table 7.4 lists these toxic chemicals and their frequency of use. 

Diesel contains benzene, toluene, ethylbenzene, and xylene (USEPA, 2004). 

Between 2005 and 2009, the hydraulic fracturing companies used 95 products containing 13 different carcinogens. These included naphthalene (a possible human carcinogen), benzene (a known human carcinogen), and acrylamide 

Chemicals Comp onents of Concern Carcinogens, SDWA-Regulated Chemicals, and Hazardous Air Pollutants 

Note HAP, hazardous air pollutant SDWA, Safe Drinking Water Act. 

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The third of the major hazards and the one with the greatest disaster potential is the release of toxic chemicals. The hazard posed by toxic release depends not only on the chemical species but also on the conditions of exposure. The high disaster potential from toxic release arises in situations where large numbers of people are briefly exposed to high concentrations of toxic material, i.e., acute exposure. However, the long-term health risks associated with prolonged exposure at low concentrations, i.e., chronic exposure, also present serious hazards. 

The Superfund Amendments and Reauthorization Act of 1986 (SARA) Tide III requires emergency planning based on threshold planning quantities (TPQ) and release reporting based on RQs in 40 CER part 355 (used for SARA 302, 303, and 304). The TPQ for acrolein is 500 lb (227 kg), and its RQ is 1 lb (0.454 kg). SARA also requires submission of aimual reports of release of toxic chemicals that appear on the Hst in 40 CER 372.65 (for SARA 313). Acrolein appears on that Hst. This information must be included in all MSDSs that are copied and distributed for acrolein. 

Gas-phase adsorption can also be used when regenerating the adsorbent is not practical. Most of these appHcations are used where the faciHties to effect a regeneration are not justified by the small amount of adsorbent in a single unit. Nonregenerative adsorbents are used in packaging, dual-pane windows, odor removal, and toxic chemical protection. 

There are three types of TAP emissions continuous, intermittent, and accidental. Both routine emissions associated with a batch process or a continuous process that is operated only occasionally can be intermittent sources. A dramatic example of an accidental emission was the release of methyl isocyanate [624-83-9] in Bhopal, India. As a result of this accident, the U.S. Congress created Tide III, a free-standing statute included in the Superfund Amendments and Reauthorization Act (SARA) of 1986. Title III provides a mechanism by which the pubHc can be informed of the existence, quantities, and releases of toxic substances, and requires the states to develop plans to respond to accidental releases of these substances. Eurther, it requires anyone releasing specific toxic chemicals above a certain threshold amount to aimuaHy submit a toxic chemical release form to EPA. At present, there are 308 specific chemicals subject to Title III regulation (37). 

M. Vandedaan and co-workers. Immunoassaysfor Trace Chemical Analysis Monitoring Toxic Chemicals in Humans, Food and the Environment, ACS Symposium Series 451, American Chemical Society, Washington, D.C., 1991. 

The 1990 Clean Air Act Amendments Hst 189 hazardous air pollutants (HAPs) that the EPA must regulate to enforce maximum achievable control technology (MACT) to standards which are to be set by the year 2000. The 33/50 project calls for reduction of emissions of 17 specified solvents to predetermined levels by 1995. The SARA statute provides a mechanism by which the community can be informed of the existence, quantities, and releases of toxic chemicals, and requires that anyone releasing specific toxic chemicals above a threshold level to annually submit a toxic chemical release form to the EPA. The status of various ketones under these regulations is shown in Table 4. 

The state of Texas controls chemical process ha2ards through its statute that estabUshed the Texas Air Control Board in 1965. In 1985, guidelines were estabUshed for evaluations of community impact of releases of 46 toxic chemicals, if Texas decides that a disaster potential exists (26). 

Toxic Substances Control Act. EPA regulates the manufacture, use, and exposure to ha2ardous or toxic chemicals under a number of laws. Eor the chemical industry, the law of prime concern is the Toxic Substance Control Act (TSCA) (10), which was passed by the U.S. Congress in 1976. The two main goals of TSCA are acquisition of sufficient information to identify and evaluate potential ha2ards from chemical substances, and regulation of the production, use, distribution, and disposal of these substances. 

Hazardous Air Pollutants. Tide 3 of the CAAA of 1990 addresses the release of hazardous air poUutants (HAPs) by requiring both the identification of major stationary sources and area source categories for 189 toxic chemicals and the promulgation of control standards. Major sources of air toxics, also referred to as HAPs, include any stationary source or group of sources emitting 10 or more tons/yr of any single Hsted toxic chemical or 25 tons/yr of a combination of any Hsted toxic. Area sources of HAPs include smaller plants that emit less than the 10 or 20 tons/yr thresholds. The major sources of HAPs are typically industrial faciHties. However, Tide 3 requites the EPA to study potential health affects associated with emissions of HAPs from electric UtiHty boilers (11). 

Potentiation is appHed to a condition where one material, of relatively low toxicity, enhances the expression of toxicity by another chemical. The result may be a larger response or more severe injury than that produced by the toxic chemical alone. A particular example is an enhancement of the absorption of a material of known toxicity by a surface-active material. 

Fig. 5. Toxic chemical dose—response curves (a) no effect (b) linear effect (c) no effect at low dose and (d) beneficial at low dose.

Isocyanates. Isocyanates in general are toxic chemicals and require great care in handling. Oral ingestion of substantial quantities of isocyanates can be tolerated by the human body, but acute symptoms may develop from the inhalation of much smaller amounts. The inhalation of isocyanates presents a ha2ard for the people who work with them as weU as the people who Hve in the proximity of an isocyanate plant. Adequate control of exposure is necessary to achieve a safe working environment. The suppHers Material Safety Data Sheets (MSDS) have to be consulted for the most current information on the safe handling of isocyanates. 

G. R. Chaudhry, ed.. Biological Degradation and Bioremediation of Toxic Chemicals, Dioscorides Press, Pordand, Oreg., 1994. 

Biphenyl is defined as a toxic chemical under, and subject to, reporting requirements of Section 313 of Tide 111 of the Superfund Amendments and Reauthori2ation Act (SARA) of 1986 and 40 CFR, Part 372 under the name biphenyl. It is identified as a ha2ardous chemical under criteria of the OSHA Ha2ard Communication Standard (29 CFR 1910.1200). 

The modem history of the military use of toxic chemical agents (1,3—5) dates from the first full-scale (chlorine) gas attack on April 22, 1915, near Ypres, Belgium in World War I. There were a few reports of the limited use of toxic chemicals since that time. The Italians employed mustard, a bUster agent, during the Ethiopian war in 1935 and 1936 the Japanese used toxic chemicals in a number of small-scale engagements in the early years of their war with China and Iraq purportedly employed both mustard and nerve gases in the 1980s. 

Toxic chemical munitions have unique characteristics in comparison to other weapons systems, reaching personnel both widely dispersed and concentrated in fortifications, ie, gases and aerosols are not bound by corners. These materials can penetrate crevices reaching personnel physically protected from high explosives. In addition, toxic chemicals are minimum-destmction weapons as regards matHriel (5). 

The Toxic Substances Control Act (TSCA) was enacted in 1976 to identify and control toxic chemical ha2ards to human health and the environment. One of the main provisions of TSCA was to estabUsh and maintain an inventory of all chemicals in commerce in the United States for the purpose of regulating any of the chemicals that might pose an unreasonable risk to human health or the environment. An initial inventory of chemicals was estabhshed by requiring companies to report to the United States Environmental Protection Agency (USEPA) all substances that were imported, manufactured, processed, distributed, or disposed of in the United States. Over 50,000 chemical substances were reported. PoUowing this initial inventory, introduction of all new chemical substances requires a Premanufacturing Notification (PMN) process. To be included in the PMN are the identity of the new chemical, the estimated first year and maximum production volume, manufacture and process information, a description of proposed use, potential release to the environment, possible human exposure to the new substance, and any health or environmental test data available at the time of submission. In the 10 years that TSCA has been in effect, the USEPA has received over 10,000 PMNs and up to 10% of the submissions each year are for dyes (382)... 

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