Single-dose exposures higher than 500 rem are probably fatal. A single dose of ~100 rem may cause a person to experience nausea or skin reddening, although recovery is likely. However, if these doses are cumulative over a period of time rather than a single dose, the effects are less severe. Long-term effects, which develop years after a high-dose exposure, are primarily cancer.
How does the stomach work?
For many years, sulfuric acid-dichromate mixtures were used to clean glassware. These solutions are corrosive and toxic and present difficulties for disposal. Their use should be avoided if at all possible. A common substitute is a sulfuric acid-peroxydisulfate solution, and commercial cleaning solutions that contain no chromium are readily available.
Introducing the TetR-Controlled Recombination-Based in Vivo Expression Technology.
Those who do not live in seismically active zones should take these accounts to heart, as well. Other natural disasters and chemical explosions themselves can set off shock waves that empty chemical shelves and result in inadvertent mixing of chemicals. The NFPA fire hazard ratings, flash points, boiling points, ignition temperatures, and flammability limits of a number of common laboratory chemicals are given in Table 4.4 and in the LCSSs (see accompanying CD). The data illustrate the range of flammability for liquids commonly used in laboratories.
Teaching laboratories may introduce low-risk infectious agents as part of a course of study in microbiology. Nanoparticles have significantly greater relative surface areas than larger particles of an equivalent mass, and animal studies have demonstrated a correlation between biological effects (toxic response) and surface area. Thus, nanoparticles represent a greater toxic hazard than an equivalent mass of the same material in larger form.
Sometimes a chemical has to be present in a tissue for a considerable time to produce injury. For example, the neurotoxic and carcinogenic effects from exposure to heavy metals usually require long-term, repeated exposure. Select appropriate procedures to minimize exposure. Use the basic prudent practices for handling chemicals, which are discussed in Chapter 6, section 6.C for all work with chemicals in the laboratory. In addition, determine whether any of the chemicals to be handled in the planned experiment meet the definition of a particularly hazardous substance due to high acute toxicity, carcinogenicity, and/or reproductive toxicity.
More chemical will be absorbed if the chemical remains in the intestine for a long time. If a chemical is in a relatively insoluble solid form, it will have limited contact with gastrointestinal tissue, and its rate of absorption will be low. If it is an organic acid or base, it will be absorbed in that part of the gastrointestinal tract where it is most fat soluble. Fat-soluble chemicals are absorbed more rapidly and extensively than water-soluble chemicals.
The MSDSs themselves may be electronic or on paper, as long as employees have unrestricted access to the documents. Be aware that some laboratories have been asked by local emergency personnel to print paper copies in the event of an emergency.
The possibility of serious injury or death by electrocution is very real if careful attention is not paid to engineering, maintenance, and personal work practices. Equipment malfunctions can lead to electrical fires. If there is a need to build, repair, or modify electrical equipment, the work should ideally be performed or, at a minimum, inspected by a trained and licensed electrician or electrical expert.
- Over time, some chemicals continue to build peroxides to potentially dangerous levels, whereas others accumulate a relatively low equilibrium concentration of peroxide, which becomes dangerous only after being concentrated by evaporation or distillation.
- The book is geared toward an industrial audience and contains basic descriptions of chemical hazards along with technical guidance.
- This chapter aims to collect and summarize the chemical properties of cobalt and some new cobalt compounds.
- Clearly, careful handling of volatile chemicals is very important; keeping containers tightly closed or covered and using volatiles in laboratory chemical hoods help avoid unnecessary exposure to inhaled chemicals.
This resource provides an excellent summary of the toxicology of more than 600 chemicals. Most entries are one to two pages and include signs and symptoms of exposure with reference to specific clinical reports. Pattyâ€™s Industrial Toxicology, 5th edition (Bingham et al., 2001). Also available on CD, this authoritative reference on the toxicology of different classes of organic and inorganic compounds focuses on health effects; hazards due to flammability, reactivity, and explosivity are not covered. International Chemical Safety Cards from the International Programme on Chemical Safety (IPCS, 2009).
3. Some common cobalt compounds
Cancer, in the simplest sense, is the uncontrolled growth of cells and can occur in any organ. The mechanism by which cancer develops is not well understood, but the current thinking is that some chemicals interact directly with DNA, the genetic material in all cells, to result in permanent alterations. Other chemical carcinogens modify DNA indirectly by changing the way cells grow.
It could be hypothesized that repression of certain genes during the in vivo colonization is as important as the induction of virulence factors. In this study, we successfully established TRIVET, representing a modified variant of the recombination-based technology, and identified 101 ivr genes of V. cholerae. As seen with other techniques, a recombination-based reporter technology has certain limitations, but also unique advantages, such as single cell expression profiling and detection of transient gene silencing during the entire infection period.
Frequency of exposure also has an important influence on the nature and extent of toxicity. The total amount of a chemical required to produce a toxic effect is generally less for a single exposure than for intermittent or repeated exposures because many chemicals are eliminated from the body over time, because injuries are often repaired, and because tissues may adapt in response to repeated low-dose exposures. Some toxic effects occur only after long-term exposure because sufficient amounts of chemical cannot be attained in the tissue by a single exposure.
However, storage of commercially obtained chemicals (e.g., in 500-g jars or 1-L bottles) should be carefully managed from the standpoint of chemical compatibility. Accidental contact of incompatible substances results in a serious explosion or the formation of substances that are highly toxic or flammable or both. Although trained laboratory personnel question the necessity of following storage compatibility guidelines, the reasons for such guidelines are obvious after reading descriptions of laboratories following California earthquakes in recent decades [see Pine (1994)].
Consult sources of information. Consult an up-to-date LCSS for each chemical involved in the planned experiment or examine an up-to-date material safety data sheet (MSDS) if an LCSS is not available. In cases where substances with significant or unusual potential hazards are involved, consult more detailed references such as Patnaik (2007), Bingham et al. (200 1), and other sources discussed in section 4.B. Depending on the laboratory personnelâ€™s level of experience and the degree of potential hazard associated with the proposed experiment, obtain the assistance of supervisors and safety professionals before proceeding with risk assessment.
Section 4.C discusses the toxic effects of laboratory chemicals by first presenting the basic principles that form the foundation for evaluating hazards for toxic substances. The remainder of this section describes how trained laboratory personnel can use this understanding and the sources of information to assess the risks associated with potential hazards of chemical substances and then to select the appropriate level of laboratory practice as discussed in Chapter 4.