I use the word ‘chemicals’ a lot, especially when talking about food or something that we use every day. I tell you that they’re dangerous without ever going into detail about why or how. Today I will do that. Whenever I say chemicals, I’m usually talking about something toxic, dangerous, or just not very good for us, but everything in the physical world around us is made of chemicals. The earth we walk on, the air we breathe, the food we eat, the cars we drive, and the houses we live in are all made of various chemicals. Living organisms such as plants, animals, and humans are also made of chemicals.
The problems usually come with chemicals that are man-made. Like everything else, we just can’t help, but reach into the pure cookie jar, take out something that isn’t ours and turn it into something we shouldn’t. Some of these include chemicals in drugs, cosmetics, workplace chemicals, household cleaning agents, and so on. Granted there are natural dangerous chemicals like arsenic. They are found in our food and air. There are far more natural chemicals in our environment than man-made ones, but both man-made and natural chemicals can have poisonous effects.
Amount or dose entering the body, toxicity of the chemical, removal from the body, and biological variation are all things that will influence the degree of poisoning caused by a chemical.
The first two I’ll talk about today and the second two I’ll talk about tomorrow.
The amount or dose of a chemical entering the body is probably the single most important factor which determines whether a chemical will cause poisoning. The amount of a chemical which causes poisoning depends on the chemical.
Water, for example, cools the body and quenches the thirst. Normally, water would be classified as a harmless chemical. But if, for instance, someone drank not just one glass, but many glasses that were being consumed one after the other non-stop, a point would be reached where beneficial effects would disappear and harmful effects would start to be noticed. In more severe cases, this kind of poisoning causes convulsions and seizures. There are reports of such poisoning in small children and in psychiatric patients. And yes, some people have even died. This lady and this guy are some proofs. The only difference between water being harmless or harmful, is directly related to the amount consumed. This relation is true for all chemicals regardless of whether they are natural or man-made.
Toxicity is a measure of the poisoning strength of a chemical. Chemicals that are only slightly toxic require large doses to cause poisoning and vice versa.
Toxicologists often use animal tests to determine whether small or large doses of a particular chemical cause toxicity.
There is a tendency to think of chemicals in terms of those which are poisonous or toxic and those which are harmless. These categories are used for convenience, but they imply that toxicity or its absence is an all-or-nothing property of a chemical. All chemicals can be toxic. It is the amount or dose taken into the body that determines whether or not they will cause poisonous effects. Poisoning, then, is caused not just by exposure to a particular chemical, but by exposure to too much of it.
Many chemicals which enter the body are excreted unchanged. Others are broken down. The breakdown products may be more toxic or less toxic than the original chemical which entered. Other chemicals still are stored temporarily in body organs and are removed over a short period of time. Eventually most chemicals and their breakdown products are removed as waste in the feces, urine, sweat or exhaled breath. A few chemicals such as graphite or silica dusts can be inhaled into the lungs where they lodge for many years and may never be completely removed.
As a general rule there is less risk of chemically caused disease if the body can break down the chemical into a less toxic product or rapidly remove the chemicals from the body.
Several characteristics of the exposed person or animal can influence the degree of poisoning which occurs. Age, sex, and individual susceptibility are some characteristics that can influence the degree of poisoning that occurs.
A one-time exposure to relatively large amounts of the chemical can overwhelm the body. The ill-health effects caused by one-time, sudden, high exposures are often called “acute toxicity” effects.
Inhalation of high concentrations of acid vapors might cause serious burns of the mouth and airways leading to the lungs, skin contact with substantial amounts of certain organic solvents that are absorbed through the skin may cause dizziness and nausea, or inhalation of dusts can cause irritation of the respiratory tract, dryness in the throat, and coughing are just some examples of acute toxicity.
Chronic toxicity is pretty much the opposite. It’s repeated exposure over a long period of time resulting in poisoning. It’s exposure from day after day over many years. The levels of toxicity may be too low to produce acute toxicity, but still can do damage as it builds up over the years.
For example, repeated exposure to dusts containing quartz can cause scar tissue in the lungs. This leads to severe and permanent lung damage or scarring.
What else do we know about acute and chronic toxicity?
Like I said before, almost all chemicals can eventually harm you in some way or another, but the adverse health effects caused by the chemical in the two types of toxicity are often quite different.
For most chemicals, more is known about the effects of acute toxicity than chronic toxicity.
In most cases, much more is known about the acute toxicity of a chemical than its’ chronic toxicity. The understanding of acute toxicity usually comes from studies with animals exposed to relatively high doses of the substances. Accidental overexposure, spills and emergencies have added to our knowledge of acute toxicity in humans. The health effects may be temporary, such as skin irritation, sickness or nausea, or they may be permanent: blindness, scars from acid burns, mental impairment and so on.
Acute toxicity is often seen within minutes or hours after a sudden, high exposure to a chemical. However, there are a few instances where a one-time high-level exposure causes delayed effects.
Unfortunately, the knowledge we have about chronic toxicity also comes from animal experiments. Scientists have also learned from studying groups of people occupationally exposed to a chemical for many years. The resulting disease occurs only because the exposure has taken place repeatedly over many years. Cancer is an example of what could happen as a result of chronic toxicity. Although there is no real proof, it is said that a one-time exposure won’t automatically cause cancer. Most of the evidence supports this conclusion.
Toxicity is a measure of the poisoning strength and is an unchanging characteristic of a chemical. Hazard is not the same. It is a variable feature of a chemical. Hazard is the likelihood that a chemical will cause poisoning, given its poisoning strength and the amounts and manner in which it is used, stored and handled. The toxicity of a chemical cannot be changed, but the hazard it presents can be controlled and minimized.
Just so you know, I’ve been having a little bit of trouble coming back from the animal cruelty topics. It’s kind of like, what now? I don’t feel like I should keep talking about them. I’ve said what I needed to say and I’ve shared just about everything I know, but then again it’s kind of like I can’t get my brain focused on anything else. It has given this overwhelmingly helpless feeling that I just can’t stand. Every topic I have in mind is so broad that I don’t know what I want to say or how I want to say it. If you have any suggestions on what you want me to talk about or any questions that have to do with the broad range of things this blog centers or something you want to try to find the answer for then feel free to leave a comment. Thanks!