Pesticides In The Home- 20 Years After Treatment?

Have you ever used the Ask The Bug Doctor feature to this web site? Many people do every month not only from America but around the world. However; Where does the Bug Doctor go when he has a question? Hopefully it doesn’t shock you that I need help from time to time on identifying insects, chemical questions or just some keen insight from the many pros I’ve come to know from around the web. One such source I have is Mr. Pest Control who is a pest control expert that fields pest control professionals questions. The following is a burning query I had which was way over my pay grade but I thought might interest you. I’ve not changed anything and have provided the links you’ll need if you decide to look at the materials yourself.

My Question Is

How long can pesticides linger in a home? My reason for asking is because of a study I found which seems impossible. It lists some products that they found inside homes that, in my mind, should have dissipated a long time ago. Chlordane is listed which was last used in 1984 and not inside. DDT is listed which goes back further still. These products I can almost see lasting this long but then chemicals like fipronil, permethrin, etc? It doesn’t say who put the chemicals there, but does say these were ‘floor wipes’ samples. How long does some of this stuff last, and why wouldn’t normal activities like mopping, etc. wash it away? Personally, I think something is flawed in the study but I can’t figure it out.


Those who read this column regularly may recognize one of my hot buttons, so at this moment I am not sure how long I’ll be ranting on with this response, but buckle up………it could be awhile. We have a few issues here, one of which is our ability to detect molecules almost down to the “single molecule” stage now, and the proper question to ask is “does this matter”. If we find a single molecule of some toxic substance in someone’s home, does it pose a health threat or should it be dismissed? Well, since rational scientists tell us that Everything Is Toxic, It Is The Dose That Is Important, hopefully this study recognized that the miniscule levels of these ancient pesticides that they may (or may not) have detected in these homes are meaningless with respect to human health. Since tests now measure substances in the parts per trillion and smaller, it becomes of little value to worry about them. But, of course, if they detect these things and their goal in the first place is to put emphasis on toxic substances in the home, then it will be a highlight of their study. 

There also is a term called “Advocative Research”, in which a result is decided ahead of time and the study designed so that the desired result will be achieved. If we remember back to the Alar debacle of 1989 it was revealed after Alar was banned, purely on the engine of emotion stirred up by an environmental group needing a cause and Meryl Streep needing publicity, that the EPA pushed the manufacturer of Alar to continue doing toxicity studies UNTIL they could cause a health problem in the lab animals. They were required to continue increasing the dose administered to the animals to such a high level it was meaningless in terms of normal human exposure, but the goal was to cause a problem, not to determine the truth. I would be concerned that, in this case you cite, that the goal was to find these old pesticide molecules still in these homes, and perhaps they were, perhaps they were not. As it was proven during the DDT days, there are a number of other, non-pesticide substances that look identical to DDT in sampling and diagnostic tests. But, if it is DDT they want to find, once something looks like DDT they form their conclusion. 

But, maybe DDT and chlordane were still present at some detectable level, and this is not necessarily unexpected. These are very persistent molecules. They are not easily degraded by environmental conditions, which is the two-headed dragon. On the plus side we can apply chlordane one time under a home and 30 years or more later it still could be preventing termites from eating that home. New materials disappear much more rapidly, resulting in the need for constant reapplications of the active ingredient. Homeowners should be careful what they ask for when they demand the removal of those persistent and effective products. And, since chemicals of any kind do not suddenly blink out of existence, but instead they degrade by what is called a “half life”, we should expect a few of the molecules, still at a detectable level with our increasing ability to detect tiny amounts, to still linger in structures. 

The half-life is that length of time required for a specific chemical substance to degrade by 50% to something else. Chemicals do degrade, after all, when exposed to sunlight, water, heat, alkalinity, or micro-organisms. So, if the half life of DDT (and I’m making this up) is 1 year, and we apply a solution of 1000 parts per million, in 1 year there should be 500 parts per million, and 1 year later 250 ppm, and then 125 ppm, etc. It takes a long time to eliminate that last little molecule, and now we can detect it in a home. But, once the level gets below a certain point it really is silly to worry about it. The problem is that there are many people who subscribe to the Single Molecule Theory – that all it takes is 1 molecule of a toxic substance to set off a chain reaction in their DNA that then leads to birth defects or cancer somewhere down the line, or maybe it shows up 3 or 5 or 10 generations later. These folks need a good stiff drink and a cigarette to calm down. 

Normal activities such as washing, fluorescent lighting, vacuuming, etc. will all act to remove molecules of pesticides, but there could be hidden pockets that avoid these activities and stick around longer, and it would be these places that thes advocates in the study would seek out for their sampling. There is an expression that when all our important needs are met (food, clothing, shelter, etc.) it gives us time to worry about the trivia. Given the immense importance of insecticides in human health, and the known problems pests pose to our health, I just don’t understand why the chemical tools are the bad guys. People tend not to understand much about the role of pests in the transmission of disease of the destruction of property, at least not in our country. Most people in the U.S. likely could not name 2 diseases spread by mosquitoes, and certainly don’t know that every 30 seconds a child dies from malaria somewhere in the world. That is just to distant from their daily lives to be a concern. 

Imagine the time and money being spent chasing a few molecules of DDT and chlordane, while at the same time 500,000 people die annually in the U.S. alone from the effects of cigarettes. Is it possible that the priorities of these groups are a bit skewed? This study very well might have detected the presence of these pesticides. What is flawed is the probable message from the study that this is important to the health of the people living in those homes. When used properly, insecticides provide a tremendous benefit to human health and happiness, while posing an insignificant risk to humans and pets.

What Say You?

About The Bug Doctor

Jerry Schappert is a certified pest control operator and Associate Certified Entomologist with over two and a half decades of experience from birds to termites and everything in between. He started as a route technician and worked his way up to commercial/national accounts representative. Always learning in his craft he is familiar with rural pest services and big city control techniques. Jerry has owned and operated a successful pest control company since 1993 in Ocala,Florida. While his knowledge and practical application has benefitted his community Jerry wanted to impart his wisdom on a broader scale to help many more. was born from that idea in 2007 and has been well received. It is the goal of this site to inform you with his keen insights and safely guide you through your pest control treatment needs.

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  • Bugafe365


  • Well put and succinct.

  • Joe

    Very interesting reading. Thank you!

  • Thank you Joe,

    I always am humbled when pest professionals take the time to read what I have offered.

  • Thespleenlesswonder

    In one breath, mr. Pest control goes from saying that people worried about low-level doses need a cigarette “to calm down” to saying that being worried about low level doese is ridiculous compared with the much greater health concern posed bby cigarettes.

    Also, he makes a valid point that we can detect minute concentrations nowadays, but he structures his arguments to suggest that the floor swipe tests have succeeded in finding the one molecule in the whole house…. which is inane.

    It doesn’t seem like it should be a big mental leap for a professional who is accustomed to the mantra that “when one is seen, many must be”….

  • Thanks for your reply sleepless wonder,

    Illustrating the absurd with absurdidty is not only a powerful way to get a point across, it is also most often humorous. 

    I believe he accomplished both.