Putting Pesticides into Perspective
As a company which has devoted many decades to Public Health Entomology and the area of Pest Management, Univar USA has been involved in the area of “pesticides”, and of course in the controversies which inherently associate themselves with this topic. The use of pesticides for controlling animals (including insects) weeds, and plant pathogens has provided the human race with immeasurable benefits by reducing disease, increasing food supplies, and protecting our property. This will not be the topic of this BugInfo article, for these benefits are things we will cover in other pest-related articles.
What is important here is for you to be able to understand what “pesticides” are, and perhaps gain this understanding from a brief historical perspective. It is important to recognize, first of all, that a pesticide is something that is used to affect living organisms in general, not just insects. Thus, we use pesticides to kill or prevent weeds, to kill or repel nuisance rodents, to kill, repel, or affect the growth of insects. We use pesticides called fungicides to kill or prevent disease organisms that harm our plants, providing us with food production that is far more efficient, or simply a more pleasing and healthy landscape or lawn in our yard. Pesticides, clearly, can provide us with tremendous benefits.
There also may be problems with pesticides, and by far this occurs when they are used in a manner that the manufacturer did not intend. It takes up to 15 years of research for a new chemical ingredient to be approved for use in the United States, and the final result will be a Product Label that tells exactly how the product shall be used, from the amount to use to the pests it is intended to control to the sites to which it may be applied. Any deviation from these clear instructions not only can lead to the creation of hazards to people, animals, or the environment, but it also is illegal.
Because of the documented problems that have occurred with pesticides in the past few decades there is a great concern among many people that pesticides are, therefore, inherently dangerous, and that there is something about them that is different from other chemicals in our daily use. I hope that this article gives you a more clear perspective on just what pesticides are. I receive many questions from the American Public, and for this article I would like to use the format of answering many of these questions.
How long have we used “pesticides”?
Humans have used pesticides throughout recorded history. Pesticides are not unique to modern laboratories, but in reality they exist by the thousands in Nature. Most plants produce chemicals in their systems to defend themselves from their enemies, the plant feeding bugs. Many minerals were long ago discovered to have poisonous qualities that could be exploited in our long history of competing with insect pests. Some of the earliest of the plant poisons that were used by humans were nicotine (from tobacco) and pyrethrum (from chrysanthemums), and they are still used in pesticide products today.
From the soil it was discovered that substances such as boric acid (from borax mines) and arsenic could kill insects or rodents that spread terrible diseases to humans, and boric acid is still widely used in formulations for cockroach and ant control today. Another natural chemical is, today, our most commonly used pesticide, and that is chlorine. We tend not to think of chlorine as a “pesticide”, but it is regulated as such and its use is to kill living organisms – bacteria and viruses – that infect swimming or drinking water and could cause potentially lethal diseases.
Aren’t “Natural” pesticides safer than Synthetic pesticides?
No, not as a general rule. The father of modern toxicology – Paracelsus – stated many centuries ago that “All substances are toxic…..there is none that is not. It is the dose that differentiates a poison from a remedy”. His wisdom states that everything around you has a toxic level, and you cannot change this quality of toxicity. Whether or not the toxic substance poses a health risk is determined by how much of it you expose yourself to, and this is referred to as the “hazard”. We can safely take aspirin for pain if we observe the guidelines on the product label, but if we ignore the instructions and take 10 times the dose we should, we run the risk of illness or death. This is exactly the case with the toxins used for controlling unwanted pests – the proper dose controls the pest and minimizes the risk to people, pets, or the environment. But, when we use the pesticide incorrectly we increase the hazard from it.
It is interesting to realize that a number of “pesticides” are now also being used medicinally, to cure or control health problems. For many years doctors have administered a common rat poison – Warfarin – to patients who had problems with blood clots, as this is an anticoagulant. At high doses it kills rodents, and at low doses it benefits heart patients. Arsenic has been a poison for many centuries, and recent studies are showing it may have some important benefits to patients suffering from leukemia, obviously used at doses well below that which would pose a toxic hazard.
So, the Dose Makes the Poison, and many synthetic, man-made pesticides are dangerous at very low levels while others are dangerous only when there is exposure to very large amounts. Similarly, “natural” pesticides may be toxic at very low doses, such as nicotine. It has a relative toxicity that places it into the most toxic category, whereby the product needs to display the words “Danger – Poison” and a skull and crossbones. In general, plant-derived pesticides tend to have low levels of toxicity, but this is not always the case, and if you use a Natural pesticide you must observe the same safety precautions as you would for any man-made product.
How long do pesticides last?
This question may be approached in two different ways:
- How long will they last in storage.
- How long will their residue last in the environment.
Generally speaking, pesticide products will last for a very long time if they are kept in cool, dry storage and in their original, intact containers. Liquid formulations may last for many years and still be usable, while dry formulations such as dusts or granules may be stable for only several years. They are more likely to suffer from a change in the molecule of the active ingredient than liquid products are. For this reason you must make every effort to buy only as much as you will need in a year or two, perhaps even in a single “buggy season”, so you aren’t storing toxic material through the winter. You also must ensure it is stored where the package cannot get wet or exposed to direct sunlight, for water and heat are two effects that help destroy pesticide molecules.
You also must ensure you mix only enough material to use on a particular application, if it is a product you will be mixing with water to spray. Once mixed in water many pesticides begin to disintegrate quickly, and it is very possible that a week or so later your spray tank may not even have a solution in it that will kill the pests. Also, no matter how good our memories may be, we will soon forget just what it was that we mixed in that sprayer, and we could end up spraying a weed poison onto our roses for the aphid problem, doing obvious damage to the roses. Better to mix up just what is needed and use it right away.
How long pesticides last in the environment also varies tremendously. Some kinds of chemicals are very stable, while others degrade rapidly. Pyrethrum, for example, is that active ingredient we extract from flowers, and it is a common ingredient in aerosol sprays for flying insect pests. Once it is released from the can the life-expectancy is only a few hours, as ultraviolet light from the sun or fluorescent lights break the molecule down quickly. An example of a long-lasting chemical, though, is chlordane, one of the Chlorinated Hydrocarbon insecticides in wide use against termites until it left the market in the 1990’s. When it was placed onto the soil under a house it might still be there 30 years later in an amount sufficient to still prevent termites from getting past it. This was a tremendous benefit to the homeowner, who did not have to pay for frequent applications of chemicals to protect the home. However, it also was an environmental concern, in that the long residual increased the chances that the active ingredient could move off site to places it should not be.
Now, the reason it lasted so long under the house was because it was protected from the elements that could eliminate it – sun, water, and heat. If the same chlordane were sprayed onto a hot asphalt driveway in July a great deal of it could be gone within just a few days. You see, there are variables. Chemicals degrade by what is called their “Half Life”, and if the half-life of Chemical A is 2 years under a specific condition, that means that 2 years after it is first applied there will be only half of it left, and two years later only half of that will remain. They don’t just suddenly blink out of existence, but degrade slowly (or quickly) until they are present at too low a level to do any good in controlling pest insects or weeds. Generally speaking, chemicals of all kinds are “food” for micro-organisms in the soil.
How dangerous are pesticides to people?
The toxicity of chemicals in general might be placed into the categories of either:
- Acute toxicity – the effect felt rapidly after an exposure to too much chemical
- Chronic toxicity – a toxic effect that may manifest itself long after the exposure, or be caused by repeated low exposures due to a cumulative effect.
With chronic toxicity the biggest concerns expressed by people are the fear that pesticides can cause cancer or birth defects, because this concern is widely publicized by the media. Whether or not this truly happens is open to vigorous debate, but here are a few facts.
- Health surveys of thousands of people who work in the pest management industries have shown that these people have no more cancer or history of birth defects than people who do not have this level of exposure to pesticides.
- Testing of animals to determine the potential for a chemical to cause cancer involves exposing the animals to extraordinary levels of the material on a daily basis for the life of the animal. The levels they receive have little relation to the trace amounts people may be in contact with in our daily lives, and sometimes the chemical is introduced into the animal in unrealistic ways just to obtain the results sought.
- The American Cancer Society has stated publicly that cancer rates in the U.S. have declined steadily for decades, with the exception of lung cancer (smoking) and skin cancer (sun exposure).
- Dr. Bruce Ames, a highly respected expert on cancer and its causes at the University of California, has stated that, as carcinogens, man-made chemicals are a negligible risk, and that 99.9% of the potential cancer-causing materials we are exposed to are present as NATURAL ingredients in the environment around us.
With respect to Acute Toxicity, the answer goes back to our earlier discussion of the toxic levels of chemicals. If you follow the instructions properly you will reduce your risk from any toxic substance to a level approaching zero risk. This pertains to medicines and household disinfectants and cleaning products as much as it does to pest control chemicals. You can safely wash paint brushes in paint thinner, or even remove some paint from your skin with it, but you would likely get very, very ill if you drank some. In fact, paint thinner is far more toxic than virtually any pesticide solution that will be applied in or around your home by a professional in pest management.
One final word on toxicity, and the hazard of today’s pesticides to people. In 1950 an average of about 200 people died each year from acute pesticide poisoning. This number is dominated by poisonings around the home due to improper use and storage of these materials. By 1995 the average number of deaths had dropped to about 8 people per year, still too many deaths, but a great trend in the right direction. The reasons for this are many, and I’d like to offer some:
- There is a reduction in the use of pesticides by homeowners as well as the professional industries, and a move toward more discrete placement of the products to control a specific pest problem.
- Pesticides are sold to the public primarily in the diluted form.
- There is a greater awareness of the hazards of pesticides and precautions, particularly the wearing of protective clothing, is increased.
- Pesticides in use today generally are far lower in toxicity than their predecessors in the ’50s and ’60s.
- New technologies have provided ways to create formulations or packages that greatly reduce our exposure to the actual pesticide ingredient, while still allowing it to affect the pest.
When will we have Safe pesticides to use?
The professional pest management industries are cautioned by regulatory agencies NOT to claim that pesticides are either “safe” or “non-toxic”, for in reality this would not be accurate. No matter how low the toxicity is of a specific chemical there still is a dose that could be harmful. What may be more accurate would be to say that pesticides CAN be used in a manner that poses no risk to you, and at the same time provides you with potentially great benefits. We still have a need for immediate elimination of certain public health pests, and pesticides provide the tool in a cost effective manner. For example, West Nile Virus is a new disease in the U.S., spread by mosquitoes and rapidly being found in mosquito and bird populations across the entire continent. It is a deadly form of encephalitis, and people deserve to be protected from it and from the mosquitoes that vector it.
There are many kinds of pesticides that approach a “non-toxic” level to people and animals, such as the biological materials used to control mosquito larvae or caterpillars on food crops. Many of the extracts from plants also have very, very low acute toxic levels. However, any of these still could cause a health concern if a sensitive person were exposed to a high dose, so caution must be used with any and all pesticides. A comparison might be made to life-saving medicines and antibiotics, which are capable of destroying the bacteria or viruses in our bodies that could cause death. At the same time, though, consuming more than the prescribed dose of these medicines could easily be an “overdose” that might kill.
The Final Word?
Pesticides perform a needed task in our lives, and without them we would begin to see a rapid increase in the presence of dangerous pests. Cockroaches are demonstrated to carry, on their bodies, dozens of pathogens they have picked up in their filthy life styles. Fleas still carry bubonic plague, and mosquitoes still carry malaria, encephalitis, and other diseases. We strive to use less pesticides and in a more careful manner, but until other methods are devised to conquer our enemies we must protect ourselves with the tools available – in the safest manner possible.
Follow directions if you use pesticides. This allows you to rid yourself of the pests that bother you without risking the health of yourself or those around you. Pesticides are chemicals, like all other chemicals, and there truly is nothing devious about them whereby they somehow set off chain reactions in your body to suddenly erupt years later as chronic problems. The dose determines the danger, and you can control this dose with proper use.