A chemical of relatively low hazard can present substantial risk and, in turn, a chemical with a high hazard might present no measurable risk under certain circumstances.

There are thousands, if not millions, of chemical substances in the world’s marketplace, and in our homes, schools, churches, workplaces, public facilities and in the environment at large. Chemicals are found everywhere. Chemicals are necessary and for the most part good; they purify drinking water, increase crop production, simplify household chores, and are used to manufacture many, if not all, products and goods. However, chemicals can also be hazardous to humans and the environment when used improperly or released uncontrollably. Hazardous uncontrolled chemical releases can occur during production, storage, transportation, handling, use, or disposal. You, your workplace, and your community are at risk if a chemical is released in harmful concentrations into the environment where you live, work, and play.

What Does Hazardous Mean?

A hazard is anything with the potential to cause harm, including hazardous chemicals. Risk is the probability of a negative outcome from exposure to a hazard. A chemical is defined as hazardous if it has one or more of the following characteristics: flammable, corrosive, toxic, or reactive. Also, chemicals are defined as hazardous if they are specifically listed by regulation. For example, the Occupational Safety and Health Administration (OSHA), the Environmental Protection Agency (EPA), the Department of Transportation (DOT) and States publish lists of chemicals deemed hazardous.

There are two types of hazards; physical and health. A physical hazard related to a chemical arises when the chemical could cause a fire, explosion, violent reaction that causes immediate physical damage. These chemicals can also present a health hazard due to their toxicity.

A chemical is a health hazard if it produces acute or chronic health effects when a person is exposed to a chemical in excess of the chemicals permissible exposure limit. An acute effect is the outcome of being over exposed to a large amount of a chemical is a short period of time, and chronic effect is the outcome of being exposed to low doses of a chemical over a long period of time. Materials that are health hazards include carcinogens, toxic or highly toxic agents, reproductive toxins, irritants, corrosives, sensitizers, hepatotoxins, nephrotoxins, neurotoxins, those which act on the hematopoietic system, and agents that damage the lungs, skin, eyes, or mucous membranes.

Consumer products are includable as a hazardous chemical only if they are used in a manner not intended by the manufacturer. For example, PAM® cooking spray would not be included if it is used in normal food preparation. However, it would be included if it is used for coating metal smelting crucibles in a foundry operation. Insecticides, rodenticides, and pesticides are always included as hazardous by the EPA’s Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA).

Biohazards are infectious agents or hazardous biological materials that present a risk or potential risk to the health of humans, animals, or the environment. A biological hazard is one that is posed to humans by a biological organism or by a material produced by such an organism. The risk can be direct through infection or indirect through damage to the environment. Biohazard materials include certain types of recombinant DNA; organisms and viruses infectious to humans, animals, or plants (e.g., parasites, viruses, bacteria, fungi, prions, rickettsia); and biologically active agents (i.e., toxins, allergens, venoms) that may cause disease in other living organisms or cause significant impact to the environment or community. They also can include CDC’s “Select Agents,” which are essentially biohazard materials with terrorist/weapons potential.

A toxic substance is one that is capable of causing injury or damage to a living organism. A wide variety of materials are considered as toxic; examples are sulfuric acid, whose action is notably corrosive; compounds of heavy metals such as tetraethyl lead, which may act as systemic poisons; selenium compounds, such as selenium dioxide; and natural products, such as the aflatoxins.

The term toxicity denotes both the capacity to cause harm to a living organism and to indicate the adverse effects caused by a chemical. The degree of harm caused to an organism by exposure to a toxic chemical generally increases with exposure level, but it is also dependent upon the type of organism, the length of exposure, the physiological status of the organism (essentially its fitness), and its developmental stage. For example, some toxic chemicals have a more serious effect upon a developing fetus than upon an adult organism.

Hazardous Material vs. Hazardous Waste

A hazardous waste is any discarded material, including hazardous chemicals, which contain substances known to be toxic, mutagenic, carcinogenic, or teratogenic to humans or other life forms; they may be ignitable, corrosive, explosive, or highly reactive alone or with other materials. A hazardous waste is always a hazardous material, although a hazardous material is not always a hazardous waste. The bottom line is that both hazardous materials and hazardous waste can be dangerous, and must be handled appropriately.

Hazard vs. Risk

A hazard is defined as the potential to cause harm; risk, on the other hand, is the likelihood of harm (in defined circumstances, and usually qualified by some statement of the severity of the harm).

The relationship between hazard and risk must be treated very cautiously. If all other factors are equal, especially the exposures and the people subject to them, then the risk is proportional to the hazard. However, all other factors are very rarely equal.

Consider the following examples:

1. Potassium dichromate is a highly toxic carcinogenic chemical used in some techniques to analyze exhaled breath for alcohol content. For this purpose it is sealed in a tube and does not become airborne. Therefore, although it is a highly hazardous substance, its use as described does not present significant risk to the user.

2. Flour is not generally considered to be a hazardous substance. A jar of it on a shelf would not have a skull and crossbones depicted on it, together with other hazard warnings, as might have been the case for a bottle of potassium dichromate. However, if a bakery worker were exposed over a period of time to airborne flour dust and/or dust by skin contact, they could develop dermatitis (an inflammation of the skin), conjunctivitis (inflammation of the eyes), rhinitis (information of the nose), and even occupational asthma, an inflammatory disease of the lungs that can cause a great deal of distress and may even be life threatening.

Thus, a material of relatively low hazard can present substantial risk, while a material with a high hazard might present no measurable risk in certain circumstances.

Categorizing Risk

The characterization of risk has both quantitative and qualitative components to it. The type of hazard and the adverse outcome associated with it are important qualitative features of “risk.” Thus, a specified probability of developing eczema dermatitis (an inflammation of the skin) would be considered a lesser “risk” than an identical probability of developing melanoma (a particularly severe form of skin cancer).

However, one needs to look more closely to be able to characterize “risk,” as distinct from simply “hazard.” The degree of exposure is an important determinant of risk. Thus, a low exposure to something that is highly hazardous may result in a low risk. Conversely, a high exposure to something of very low hazard may result in a moderate or even high risk. Every reasonable attempt must be made to quantify an exposure in order to then proceed to attribute a measure of risk to it. The probability of an adverse outcome (i.e., the likelihood of a certain risk) can be expressed in various ways.

Statements about causation often depend on certain assumptions. When an assumption about causation is wrong, then any associated measure of risk, however accurate numerically, can provide misleading information if it implies that the likelihood of a certain unwanted outcome (e.g., cancer, asthma) is specifically and undoubtedly caused by the stated exposure to a particular hazard. Therefore, statements about risk must be guided by indications of the uncertainty that may be associated with them.

One may wish to know what steps have contributed to a particular risk being so high and/or what steps can be taken to reduce the risk; for example, to control the risks from occupational exposures. The cost of risk reduction measures and their benefits will need to be considered.

Risk Acceptance vs. Risk Aversion

Although the scientific community has a very important role to play in measuring risks and in presenting this information in as clear a manner as possible, with appropriate cautions about uncertainty, it remains a responsibility of society to determine what is tolerable and acceptable based on social, political, cultural, and even economic considerations.

Many hazards cannot be abolished in the sense that they are completely gotten rid of. Therefore, to reduce risk, more often than not it becomes a question of reducing exposure. In some countries, the goal for reducing occupational risks to health is to achieve a situation where “exposure should be controlled to a level to which nearly all the population could be exposed day after day, without adverse affects of health.”

In future articles, we will discuss techniques and practices for identifying hazards, assessing the specific risks of such hazards, and using the findings to select and implement controls appropriate to reduce risk to acceptable levels in support of both safe and productive work outcomes.