Toxic substances, test atmospheres

RL SOP No. 70-3, dated June 1, 1967, describes methods used at Edgewood for searching for and selecting toxic chemicals. Some of the details In connection with exposure of human volunteers to experimental irritant chemicals are described. Human volunteers were exposed to compounds after review of animal screening data and approval by committees based on a conclusion that the experimental chemicals were safe for human use. Generally, two volunteers were exposed to each substance. Subjects were exposed in a wind tunnel at an airspeed of 5 mph and were asked to resist leaving the test atmosphere (up to 1 min) until exposure was unbearable. 

A detailed protocol for laboratory validation of sampling and analytical methods for toxic substances in workplace environments is given in Figure 1. The literature was searched and a method of sampling and analysis was selected. The next step was to evaluate and, if necessary, develop an analytical method that was compatible with the sampling medium. If a satisfactory analytical method became available only then did we undertake generation of a test atmosphere. Then samples were collected with the appropriate collection medium. Both capacity and collection efficiency were evaluated. 

Generation of Test Atmospheres of Toxic Substances for Evaluation of Air Sampling Methods... 

Avoidance of "routine" exposure Develop and encourage safe habits (23) avoid unnecessary exposure to chemicals by any route (23). Do not smeU or taste chemicals (32). Vent apparatus which may discharge toxic chemicals (vacuum pumps, distillation columns, etc.) into local exhaust devices (199). Inspect gloves (157) and test glove boxes (208) before use. Do not allow release of toxic substances in cold rooms and warm rooms, since these have contained recirculated atmospheres (209). 

In evaluating confined space accidents in the past, certain scenarios seem to continuously occur. These included the failure to recognize an area as a confined space failure to test, evaluate, and monitor for hazardous atmospheres failure to train workers regarding safe entry and failure to establish rescue procedures. At times, either natural or mechanical ventilation is enough to make the space safe, which can be provided prior to confined space entry. Appropriate atmospheric tests must be performed to check for oxygen deficiency, explosive concentrations, and toxic substances in the confined space before entry. The atmosphere inside the confined space mnst be frequently tested or continuously monitored during the conduct of work. 

Polarographic also can be utilized for the determination of many organic compounds present in the air, e.g. in the vicinity of factories, in the industrial atmosphere, etc. In [23] are listed compounds like formaldehyde, acrolein, acetaldehyde, furfurol, hexachlorbutadiene, and nitro-cyclohexane. The tested air is passed through a trap containing the supporting electrolyte. Application of electrochemical detection in HPLC to the measurement of toxic substances in air is the subject of a paper[24]. Derivatives of phenols and amines were chosen as examples. 

Are appropriate atmospheric tests performed to check for oxygen deficiency, toxic substances, and... 

Plant-, soil-, and sediment-dwelling organisms have other potential routes of exposure that may be used in toxicity testing. Plants are often exposed through the soil or to an atmospheric deposition. Soil invertebrates are often placed in a standardized soil laced with a particular concentration of the test substance. Sediment tests are usually with contaminated sediments or with a material added to a standardized sediment. 

EVP is the substance s vapor pressure in mmHg at 20°C ATC (which has the same value as ERPG-3) is its acute toxicity concentration in ppm, defined as the lowest reported concentration based on recognized scientific test protocols that can cause death or permanent injury to humans after a single exposure of 1 hour or less. The constant 760 converts the vapor pressure from mmHg to atmospheres. 

The level of protection selected should be based on (1) the type and measured concentration of the chemical substance in the ambient atmosphere and its toxicity, and (2) the potentials for exposure to substances in air, splashes of liquids, or other direct contact with material while doing work. In situations where the type of chemical, concentration, and possibilities of contact are not known, the appropriate level of protection must be selected based on professional experience and judgment until the hazards can be better identified. This may require a person to suit up in a Level A or B PPE and investigate/test the atmosphere/area to determine the hazard level. 

---