OBTAINING AND USING

CHEMICAL INFORMATION

T.R. Consulting, Inc.

February 2003 Safety Article

Written and compiled by:

Tony Rieck

Copyright 2003 T.R. Consulting, Inc.

http://www.trconsultinggroup.com/

T.R. Consulting, Inc. regularly publishes safety and environmentally related articles on our website at http://www.trconsultinggroup.com/safety/archive.html. These articles are a free service provided by T.R. Consulting, Inc. to all interested parties in order to promote safety and environmental awareness. T.R. Consulting, Inc. also provides safety training information and services. Information about our safety training programs can be accessed at http://www.trconsultinggroup.com/safety/.

GENERAL

Employees working on sites that can cause injury or illness need to conduct three basic steps:

* Recognition

* Evaluation

* Control

These steps are not necessarily sequential, but are generally repeated continually at a site as more is learned about the site and as the characteristics of the site change due to activities conducted at the site.

Recognition means knowing what you might be exposed to and how it acts in the environment or interacts wit your body. For a petroleum service worker, this task is relatively simple when compared to someone approaching a site with hundreds of unlabeled drums. The basic characteristics and hazards associated with petroleum products are relatively well understood. On the other hand, it is impossible to assess all of the potential hazards of an unidentified chemical or group of chemicals. The more that is known about a site and the chemical hazards on the site, the easier the recognition process becomes.

The more that is known about the chemicals involved, the easier the initial hazard recognition process becomes.

Some information that might be useful includes:

• Specific Gravity - will it float on water? Will it sink in water?
• Vapor Density - is it lighter than air or will it tend to accumulate in low-lying areas and confined spaces?
• Flammability - will it emit vapors that could burn or explode? How flammable is it?
• Solubility - if it reaches water, will it dissolve into the water or remain separated from it?
• Reactivity - if it is exposed to other chemicals on site, will an adverse reaction occur?
• Toxicity - how toxic is the chemical?
• Routes of Exposure - how can it enter the body?

The above information can help to build a body of information that can be used to recognize the potential problems posed by the release of a material into the environment.

The material safety data sheet (MSDS) published by the manufacturer or the NIOSH/OSHA “Pocket Guide to Chemical Hazards” are good reference tools for aid in determining the level of risk and the routes of exposure associated with a chemical.

Once this information is known, it is time to evaluate real and potential effects. Evaluation is a process of assessing real versus potential hazard. In other words, evaluation is the process of determining the level of risk associated with exposures at a site. A tanker car damaged in an accident is only a potential hazard if the tank did not rupture. The hazard to the public from a gas line rupture at a remote site is far less than from a rupture in close proximity to a school. The presence of gasoline vapors in an excavation where gasoline tanks have been removed from the ground may be shown through monitoring to pose a flammability hazard or to exist at such low levels that site personnel will not be adversely exposed. Again, the worker is presented with a need to understand the chemical’s properties in order to properly evaluate the potential for harm.

Some information that could be useful evaluating the risk associated with exposure to a chemical (in addition to the information discussed above) includes:

• What exposure concentrations considered immediately dangerous to life and health (IDLH)?
• What are safe exposure thresholds – Permissible Exposure Limits (PELs – OSHA), Recommended Exposure Limits (RELs – NIOSH), and the Threshold Limit Values (TLV – ACGIH)?
• What is the Lower Flammable or Explosive Limit (LFL/LEL)?
• Is the chemical considered a carcinogen?
• What are the routes of exposure and target organs?
• What are symptoms of overexposure?
• What first aid measures should be available?

Once the identity of the chemical is known, the risks associated with it identified and the site has been evaluated, it is easier to prescribe appropriate controls to prevent overexposure of site personnel, protect the public and to minimize environmental impacts. Controls include engineering controls such as ventilation, wetting of dusts, protective clothing and respiratory equipment. It is preferable to eliminate potential exposures to site personnel and the public. When engineering controls are insufficient to provide for the safety of site personnel, personal protective equipment is assigned which will reduce employee exposures below published safe exposure limits.

CHEMICAL PROPERTIES

Using the information provided about a chemical requires an understanding of the terms used to describe the chemical. Several of the more common terms used to describe a chemical’s physical properties and exposure limits are listed below:

• Specific Gravity – is a comparison between the chemical and water. Water is assigned a specific gravity of 1.0. A chemical with a specific gravity less than 1.0 will float. A chemical with a specific gravity greater than 1.0 will sink.
• Vapor Density – is a comparison of the chemical’s vapors/gases with air. Air is assigned a vapor density of 1.0. A chemical with a vapor density of 1.0 or less will readily dissipate (float away) in the air. A chemical with a vapor density greater than 1.0 will tend to accumulate in low-lying areas and near to the ground. A rule of thumb for vapor density (as it is not always included in chemical property information) is that, if the chemical is a liquid at ambient temperatures (~73 F), the vapor density will be greater than 1.0. Remember, this is a “rule of thumb”, not an absolute truth.
• LEL/LFL – the lower explosive limit and the lower flammable limit are the same value and are indicated by the percent of the chemical that must be present in the air to create an atmosphere that can ignite when exposed to an ignition source. For example, gasoline has an accepted LEL/LFL of 1.4% (14,000 ppm) in air. When 1.4% of the ambient atmosphere is comprised of gasoline vapors, the atmosphere is said to have reached the LEL/LFL for gasoline. When measuring the atmosphere in enclosed spaces with a combustible gas indicator, the reading is termed in regard to the LEL. When measuring the atmosphere in open areas with a combustible gas indicator, the reading is termed in regard to the LFL. The UEL/UFL is the upper explosive/flammable limit and the range between the LEL (LFL) and the UEL (UFL) is termed the explosive (flammable) range.
• Solubility – how much of a chemical will dissolve (technically, blend uniformly at the molecular or ionic level) in water. While solubility applies to the ability of any solute material to dissolve uniformly in any number of substances (i.e. solid in liquid/liquid in liquid/gas in liquid/gas in gas), the solubility expressed in MSDS and the NIOSH Pocket Guide is with regard to water.
• Reactivity – describes any substances that should not be brought into contact with the chemical. A chemical that is reactive with another is said to be incompatible.
• Carcinogen (marked as a “Ca” in the Pocket Guide under exposure limits) – is a substance that is known or suspected of causing cancerous growths in living tissues.
• Immediately Dangerous to Life and Health (IDLH- not on many MSDSs) – a level of exposure to a chemical where an unprotected individual exposed for 30 minutes could be expected to either die or suffer irreversible health effects.
• Routes of Exposure – are the ways that chemicals can enter into the body. Inhalation (breathing), ingestion (eating), skin/eye contact (causing damage to the skin or eyes), and skin absorption (reaching the blood system by traveling through the skin) are the noted ways for a chemical to enter the body. Another route, though neglected by chemical information sources, is injection. Injection can be intentional such as the introduction of IV drugs or unintentional such as caused by exposure to failed high-pressure (especially hydraulic) systems.
• Permissible Exposure Limit (PEL) – is the legal safe exposure limit published by OSHA for the average safe exposure of an individual over an eight hour day. The selection of personal protective equipment (PPE) is required to maintain the individuals exposure below this limit. Exposures to airborne contaminants below this level do not require the use of respirators. OSHA also publishes short-term exposure limits (STEL), ceiling limits (C), and peak exposure concentrations (P) that, when they exist, must be considered when determining compliance with the PEL
• Recommended Exposure Limit (REL) – is the safe exposure limit published by NIOSH for the average safe exposure of an individual over a ten hour day. NIOSH also publishes an STEL to be used in determining compliance with this standard. If a PEL does not exist for a chemical, the REL (when there is one) is used for exposure determination purposes.
• Threshold Limit Value (TLV) – is the safe exposure limit published by the American Conference of Governmental and Industrial Hygienists (ACGIH). ACGIH also publishes a STEL to be used in determining compliance with this standard. When neither a PEL nor an REL exists for a chemical, the TLV is used for exposure determination purposes. Note: not all chemicals will have PELs, RELs or TLVs. In such cases, a qualified individual (such as a CIH) should make determinations as to the degree of allowable exposure for employees.

Other important physical properties may also be available.

- Vapor pressure is the characteristic pressure exerted by a vapor in equilibrium with its liquid or solid form against the atmosphere. The vapor pressure increases with temperature. It is essential to understand the effects of vapor pressure when using a pump to “lift” a liquid in order to avoid cavitation of the pump.

- Viscosity is the resistance to flow exhibited by a liquid.

- Ionization Potential (IP) is the amount of energy that must be applied to a chemical to remove the outermost electron and impart a measurable charge. The NIOSH Pocket Guide is the only readily available source with this information that is necessary for the proper operation of Photo Ionization Detector (PID) or the Flame Ionization Detector (FID).

- Molecular Weight is the sum of the atomic weights of the atoms in a molecule.

Both the MSDS and the NIOSH Pocket Guide provide information on target organs, symptoms of exposure and first aid measures to be implemented when exposure occurs. The NIOSH Pocket Guide contains numerous abbreviations that are explained in supplementary sections of the book. Importantly, the NIOSH Pocket Guide provides information on appropriate selection of respirators and indications when other safety devices or measures are required (such as quick drench or periodic change of protective clothing). For more complex chemicals, the MSDS provides breakdowns on the exposure potential for each of the components. A proper approach to proper assessment is to incorporate both the MSDS and the NIOSH Pocket Guide into routine use.

Special note regarding PEL information: In July 1992, the 11th Circuit Court of Appeals in its decision in AFL-CIO v. OSHA, 965 F.2d 962 (11th Cir., 1992) vacated more protective PELs set by OSHA in 1989 for 212 substances, moving them back to PELs established in 1971 (these values were extracted from the 1968 ACGIH TLV Booklet). The appeals court also vacated new PELs for 164 substances that were not previously regulated. The substances for which OSHA PELs were vacated on June 30, 1993 are indicated by the symbol "†" following OSHA PEL in this column. For chemicals that were affected by this lawsuit, special consideration should be given to decisions affecting employee exposures in the field as the stated PEL may be under protective.