Toxic materials exposure limits

The Phoenix diazomethane process can produce over 200 ty of chloroketone with an overall yield of 90% and in very high purity. This demonstrates a remarkable use of a highly explosive and toxic material (exposure limit of 0.2 ppm averaged over 8h) controlled by conhnuous generation and reaction. Thus, over 60ty" diazomethane are consumed per annum, but the maximum accumulated at any time is less than 80 g. 

Materials information includes toxicity, permissible exposure limits, physical properties, reactivity, corrosivity, thermal and chemical and hazardous effects of inadvertent mixing of different materials.Process information consists of 1) process flow diagrams, 2) process chemistry descriptions, 3) maximum amounts of chemicals, 4) safe ranges for temperatures, pressures, flows oi 5) evaluation of the con.sequences of deviations. 

Toxicity Data on Af- Vinyl-2-Pyrrolidinone. Results of a chronic inhalation study in rats warrant a review of industrial hygiene practices to assure that VP vapor concentrations are maintained at a safe level. One of the manufacturers, ISP, recommends that an appropriate workplace exposure limit be set at 0.1 ppm (vapor) (9). Additionally, normal hygienic practices and precautions are recommended, such as prompt removal from skin and avoidance of ingestion. In case of accidental eye contact, immediately flush with water for at least 15 minutes and seek medical attention. Refer to the manufacturers Material Safety Data Sheets for more detailed information. Table 3 provides some toxicity data. 

Toxic materials shall be at or below the threshold limit value, permissible exposure hmit, or other approved industrial hygiene guideline. 

Information pertaining to the hazards of the chemicals used in the process. This should contain at least the following information toxicity, flammability, permissible exposure limits, physical data, reactivity data, corrosivity data, thermal and chemical stability data, and hazardous effects of inadvertent mixing of different materials that could occur. 

Health Hazards Information - Recommended Personal Protective Equipment Eye protection Symptoms Following Exposure Vapors from very hot material may irritate eyes and produce headache, drowsiness, and convulsions General Treatment for Exposure Remove fresh air. Wash affected skin areas with water. Flush eyes with water Toxicity by Inhalation (ThresholdLimit Value) 5 mg/m Short-Term Exposure limits Not pertinent Toxicity by Ingestion Grade 1 LDjq 5 to 15 g/kg Late Toxicity Birth defects in rats polyneuritis in humans Vapor (Gas) Irritant Characteristics Not pertinent liquid or Solid Irritant Characteristics No appreciable hazard. Practically harmless to the skin Odor Threshold Data not available. 

Substances hazardous to health include substances labelled as dangerous (i.e. very toxic, toxic, harmful, irritant or corrosive) under any other statutory requirements, agricultural pesticides and other chemicals used on farms, and substances with occupational exposure limits. They include harmful micro-organisms and substantial quantities of dust. Indeed any material, mixture or compound used at work, or arising from work activities, which can harm people s health is apparently covered. 

Although there is much controversy over using animals in tests such as these, the information is an essential part of the legal testing required when new chemicals are introduced onto the market in significant quantities. These and other toxicity test results are used to help develop Material Safety Data Sheets, establish Occupational Exposure Limits and guidelines for use of appropriate safety equipment. 

Measurement of exposure can be made by determining levels of toxic chemicals in human serum or tissue if the chemicals of concern persist in tissue or if the exposure is recent. For most situations, neither of these conditions is met. As a result, most assessments of exposure depend primarily on chemical measurements in environmental media coupled with semi-quantitative assessments of environmental pathways. However, when measurements in human tissue are possible, valuable exposure information can be obtained, subject to the same limitations cited above for environmental measurement methodology. Interpretation of tissue concentration data is dependent on knowledge of the absorption, excretion, metabolism, and tissue specificity characteristics for the chemical under study. The toxic hazard posed by a particular chemical will depend critically upon the concentration achieved at particular target organ sites. This, in turn, depends upon rates of absorption, transport, and metabolic alteration. Metabolic alterations can involve either partial inactivation of toxic material or conversion to chemicals with increased or differing toxic properties. 

H. Safety considerations. The Occupational Safety and Health Administration (OSHA), US Department of Labor, standard entitled Occupational Exposure to Hazardous Chemicals in Laboratories (29 CFR 1910.1450) makes it necessary to address safety issues in the SOP. The standard requires laboratories that use hazardous chemicals to maintain employee exposures at or below the permissible exposure limits specified for these chemicals in 29 CFR Part 1910, Subpart Z. Hazards associated with any specific chemicals used in a method must be addressed so that the user has the information needed to follow the Chemical Hygiene Plan for their laboratory. The method developer should limit the use of hazardous chemicals where feasible. The use of toxic and/or carcinogenic reagents should be avoided or eliminated as much as possible. Additionally, the cost of disposal is increasing and could impact the practicality of a method. Material Safety Data Sheets for the analyte(s) and any unusual or hazardous reagents should be provided for the user. 

The acceptable limits for toxic exposure depend on whether the exposure is brief or prolonged. Lethal concentration for airborne materials and lethal dose for non-airbome materials are measured by tests on animals. The limits for brief exposure to toxic materials that are airborne are usually measured by the concentration of toxicant that is lethal to 50% of the test group over a given... 

Where complete containment is impractical, exhaust ventilation (preferably to a scrubber) can limit or eliminate exposure to toxic materials. The exhaust ventilation rate (velocity or volumetric rate) may be calculable for volatile liquids from spill size and vapor pressure (U.S. Environmental Protection Agency, Risk Management Program Guidance for Offsite Consequence Analysis, Appendix D, Equation D-l, 1999), but tests to determine concentrations in air usually would be needed for dusty processes and fugitive releases of gases. 

To some people, the concept of an acceptable limit of exposure to a toxic material is anathema. Nevertheless, in recognition of practical realities, various authorities, federal and state in the U.S., and federal and... 

Threshold Limit Value-Short Term Exposure Limit (TLV-STEL) - the concentration to which workers can be exposed continuously for a short period of time without suffering from (1) irritation (2) chronic or irreversible tissue damage or (3) narcosis of sufficient degree to increase the likelihood of accidental injury, impair self-rescue, or materially reduce work efficiency, provided that the daily TLV-TWA is not exceeded. It is not a separate independent exposure limit rather, it supplements the TWA limit where there are recognized acute toxic effects from a substance whose toxic effects are primarily of a chronic nature. STELs are recommended only where toxic effects have been reported from high short-term exposures in either humans or animals. 

After assessing the technical literature, a summary document (Figure 5) of the biological effects data is prepared for review by CACPH Advisory Panel and TMAC. This review results in a recommendation to draft a Toxic Material Advisory report which contains an interim exposure limit in additional pertinent health and safety requirements. The draft Toxic Material Advisory report is then reviewed by independent consultants. These consultants attend a 1-2 day meeting to evaluate the document and the appropriateness of the interim exposure limit. The independency of the review meeting is assured by having one of CACPH Advisory Panel member chair the committee to ensure that the review process proceeds in an orderly manner. CACPH s staff participation at this meeting is only to provide overview on the information that is available for review. 

Toxicity data are used to assess occupational exposure hazards associated with materials used in a process and are communicated through the use of Permissible or Occupational Exposure Limits (PEL or OEL). OELs are usually set based on a combination of the inherent toxicological hazard of a chemical and a series of safety factors such as intra-species variability in test results, the nature and severity of the effect, and the adequacy and quality of the information. OELs are set to protect workers under the general assumption that they are being exposed to any... 

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