Together with the bicarbonate, this ensures that the stomach wall itself is not damaged by the hydrochloric acid.
Hydrochloric Acid Production
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.
Corrosive effects occur not only on the skin and eyes but also in the respiratory tract and, in the case of ingestion, in the gastrointestinal tract as well. Corrosive materials are probably the most common toxic substances encountered in the laboratory.
An additional hazard is that a compound can enflame so rapidly that it produces an explosion. Proper use of substances that cause fire requires knowledge of their tendencies to vaporize, ignite, or burn under the variety of conditions in the laboratory. Whether a suspected carcinogenic chemical is treated as a PHS in the context of a specific laboratory use is affected by the scale and circumstances associated with the intended experiment. Trained laboratory personnel must decide whether the amount and frequency of use, as well as other circumstances, require additional precautions beyond the basic prudent practices of section 6.C.
- Some chemicals such as dimethyl sulfoxide actually increase the penetration of other chemicals through the skin by increasing its permeability.
- The duration and frequency of exposure are also critical factors in determining whether a chemical will produce harmful effects.
- For most chemicals, a threshold dose has been established (by rule or by consensus) below which a chemical is not considered to be harmful to most individuals.
- The are a number of ways in which acid production can be decreased.
As mentioned in Chapter 2, Paracelsus noted that the dose makes the poison and is perhaps the most important concept for all trained laboratory personnel to know. For example, water, a vital substance for life, results in death if a sufficiently large amount (i.e., gallons) is ingested at one time. On the other hand, sodium cyanide, a highly lethal chemical, produces no permanent (acute) effects if a living system is exposed to a sufficiently low dose. The single most important factor that determines whether a substance is harmful (or, conversely, safe) to an individual is the relationship between the amount (and concentration) of the chemical reaching the target organ, and the toxic effect it produces. For all chemicals, there is a range of concentrations that result in a graded effect between the extremes of no effect and death.
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.
laboratory floors are part of a general pattern of bad housekeeping that can also lead to serious accidents. Wet floors around ice, dry ice, or liquid nitrogen dispensers can be slippery if the areas are not carpeted and if drops or small puddles are not wiped up as soon as they form.
The adequate protection and restoration of soil ecosystems contaminated by heavy metals require their characterization and remediation. Contemporary legislation respecting environmental protection and public health, at both national and international levels, are based on data that characterize chemical properties of environmental phenomena, especially those that reside in our food chain .