For the next few articles, I would like to talk about toxicology and hazard communication, or “HazCom,” which often appears in the top 10 of Occupational Safety and Health Administration (OSHA) citations. As the name implies, HazCom is the communication of chemical hazards to the workforce. We also call it the “right to know.”

OSHA estimates at least 32 million workers face potential exposure to one or more chemical hazards in the workplace. Experts estimate these exposures result in roughly 22% of workplace diseases and injuries. Depending on the toxicology of the chemical and type of exposure, injuries or illnesses may show up within seconds, minutes or hours, or may not show up for weeks or even years.

What is Toxicology?

Any HazCom conversation needs to start with what we mean when we talk about toxicology. Toxicology is the study of the effects of poisons and chemicals on the body. It helps us understand the potential dangers that chemicals we work with could pose if spilled, misused or handled poorly. Drillers can encounter chemicals every day — at home and at work. It is important to know that some of those chemicals can damage our health based on amount of exposure we receive, the nature of the chemical and the manner of exposure. Individual factors, like gender, age, ethnicity and physical fitness, can all play a part in determining the damage a chemical may (or may not) do to us.

OSHA defines hazardous and toxic substances as any chemicals in the workplace capable of causing harm. The term “chemicals” includes dusts, vapors and common materials such as well treatment products, fuels and solvents. All substances are potentially toxic, from the silica dust created when air drilling to the sunshine that makes a spring day seem like summer (sunburns, anyone?). Water can even prove toxic. A woman died of water intoxication in 2007 in California after a radio station contest to see who could drink the most water and hold it without going to the bathroom. No one is exactly sure how much water she drank, but it was thought to be around 2 gallons.

What is Toxicity?

What is toxicity? The potential a substance has for causing harm. This differs from the hazard a substance poses. Imagine a highly toxic chemical buried in concrete hundreds of feet below ground. The chemical remains toxic, but the likelihood it will cause harm (that is, the hazard it poses) falls dramatically. Now, imagine we drill and happen to intersect that toxic substance. We have not changed the toxicity of the substance, but we’ve greatly increased the hazard to ourselves. So, a substance’s “hazard” is the likelihood that it will cause harm.

What is toxicity? The potential a substance has for causing harm. This differs from the hazard a substance poses.

The more toxic a material, the smaller the amount of necessary exposure before harmful effects. The lower the toxicity, the greater the quantity necessary for harmful exposure. You’ll see two ways of showing toxicity on the safety data sheets for a chemical: LD50 and LC50. LD50 applies to ingestion or skin exposure. LD50 represents the median “lethal dose” for a chemical. If a substance has median lethal dose of 20 mg, that dosage proved fatal to half of the animals in a test study. LC50 applies to airborne chemicals. LC50 represents the median “lethal concentration” of a chemical. Similar to LD50, LC50 tells us how much of a dust, vapor or gas that, when breathed in, would kill 50% of test animals. The lower the LC50 or LD50, the more toxic the substance.

Industrial hygienists like to say the “dose makes the poison.” What does that mean? The concentration of a chemical multiplied by the exposure time equals the dose. For shorthand:

 Concentration x Time = Dose

When you think about chemical exposure, consider both concentration and time. Take alcohol, for example. Most of us have had a drink. Sometimes, the concentration gets the better of us as the hours pass. This lag, however, can present problems. Depending on the amount of alcohol we drank, our actual dose may not become clear until enough time passes. In extreme cases, you may not understand you’ve had a problematic (or even fatal) dose until it’s too late. The “dose” for any toxic substance works the same. We react differently to chemicals based on our health, age, sex, genetics and race, but the equation — concentration times time equals dose — remains the same.

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We’ve laid the basis for a HazCom discussion by defining toxicology, toxicity and dosage. Next time, we’ll talk about different types of chemical exposure and what our body does when we’re exposed.

Until next time, stay safe and keep turning the right.