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Indoor pesticide exposure:
Here we describe the detection of and risks of exposure to pesticides applied indoors in buildings. We discuss methods to reduce indoor pesticide exposure as a step in improving health and indoor air quality in homes. Our page top photo shows an abandoned pesticide bottle found during a home inspection.
When we find old pesticide containers indoors we caution home buyers that a previous owner may have been applying chemicals without proper expertise. Read the label and use pesticides as directed.
Watch out: OPINION: don't panic about insects or bugs that you may see on or around your home.
A single bug like the one shown at left (clambering around on our garage door) does not merit a declaration of chemical warfare. Most insects seen on or around homes are harmless and should not be attacked.
The health risks to humans from overdoing chemical sprays and treatments applied in a panic can be significant.
Worse, misapplication of pesticides inside the home can lead to serious indoor health hazards for the building's human or pet occupants.
On the other hand, as our photo at left (termite mud tubes) illustrates, even with care to avoid or fix building leaks (a key attractant to classes of termites, carpenter ants, and other wood destroying insects), is not always enough.
Sometimes it may be necessary to consult with a professional pest inspector or pesticide applicator. See INSECT INFESTATION / DAMAGE for details about preventing or correcting problems from wood destroying insects.
Pesticides are a special class of organic chemicals designed
to kill living organisms. In addition to the compounds used
in the home and garden, the class of chemicals regulated as
pesticides also include kitchen and bath disinfectants, flea
and tick products, and swimming pool chemicals.
cases, both the active ingredient targeted to one or more
pests and the “inert” carriers are organic chemicals that are
toxic to humans.
Studies indicate that up to 80% of most people’s exposure
to pesticides occurs indoors and that measurable
levels of up to a dozen pesticides have been found in the
air inside homes.
Because of its widespread use for over
30 years, more than 80 percent of Americans already have
traces of Dursban in their bodies, according to the Centers
for Disease Control. Another study found Dursban in the
carpet dust of 67 percent of homes surveyed.
Also, remember that a pesticide found “safe” to use
today may be determined to be unsafe tomorrow. Chlordane,
the most widely use termiticide for decades, was
banned in 1988 because of its toxicity to humans and its
persistence in the environment. It was largely replaced by
Dursban (chlorpyrifos), an organophosphate.
the most widely used pesticide in the United States
until it was phased out starting in 2000, along with the
popular pesticide diazinon, because of the risks they posed
to humans, especially to the growth and nervous system
development of children.
Health Effects of Exposure to Pesticides
Our photo (left) shows drill marks we found in the rim joist of an older home in the Hudson Valley of New York.
As we explain in detail at INSECT INFESTATION / DAMAGE, these drill marks were evidence of an amateur attempt at pesticide application: the location, irregularity, angle, and other details of these drill marks made us nervous.
We tested a sliver of this wood and found that it was still contaminated with Chlordane - misapplied on the building interior.
There are nearly 900 pesticides registered
for use in the United States. Nearly all are at least
moderately toxic to humans and pets and many are highly
Symptoms of overexposure to pesticides include irritation
to the eyes, nose, and throat, headaches, blurred
vision, nausea, loss of coordination, muscular weakness,
and damage to the central nervous system, liver, and kidneys.
Every registered pesticide has a “signal” word on the
label, ranking the level of toxicity to humans, as follows:
Danger—Poison: highly poisonous to humans or other animals
Danger: poisonous or corrosive
Warning: moderately hazardous
Caution: least hazardous
Some of the more problematic pesticides used in and
around households include:
Organophosphates and carbonates.
classes of chemicals, including Dursban and Lorsban,
kill insects by disrupting their nervous systems. Studies
indicate that they affect the birth weight and neural
development of infants.
From 1993 to 1996, nearly
63,000 reports were made to U.S. poison control centers
about residential exposures to organophosphates,
according to the U.S. EPA. Almost 25,000 of these
incidents involved children under 6, who are particularly
vulnerable to organophosphate poisoning and at
least 482 resulted in hospitalization.
Mothballs - human exposure hazards: Mothballs contain either of the chemicals
paradichlorobenzene or naphthalene. Paradichlorobenzene
is classified as a possible human carcinogen by
the EPA, and its vapors can irritate skin, eyes, and the
respiratory tract. Large doses can damage the liver.
Mothballs are not intended to be placed in open spaces such as rooms, closets, or vehicles. Rather they should be used in an airtight space such as a clothes storage bag. 
Mothballs are fumigants that will dissolve or sublime at lower temperatures; mothballs thus work by a process of sublimation - the solid ball of chemicals converts directly to a gas that enters the air nearby.  But believe it or not mothballs or moth crystals may also be a child hazard if eaten - as has happened. 
Symptoms of exposure to
naphthalene include headache, nausea,
dizziness, and difficulty breathing.
Paradichlorobenzene is also a potential
hazard, although typically less so
compared to naphthalene. ... Eating just one mothball containing
naphthalene can damage a young child’s
red blood cells.... 
Exposure to naphthalene promotes hemolytic anemia,
associated with fatigue in mild cases and acute kidney
failure in severe cases. Poisonings of infants have
been reported after dressing the children in clothing
stored in naphthalene mothballs.
How to Reduce Indoor Exposure to Pesticides
When possible, the best approach
is to find non chemical approaches to pests. When chemicals
must be used, choose the least toxic option, and use it
outdoors, if possible, and away from areas used by pets
and children who will track it back into the house.
Use insect-resistant construction materials and
techniques. The use of termiticides can be reduced or
eliminated by careful detailing of entry points, and by
using alternative building materials, such as steel,
masonry, concrete, insulating concrete forms (ICFs),
or treated lumber. Borate-treated lumber is nontoxic
to humans and very effective against termites and
carpenter ants as long as it is not exposed to regular
Use non chemical methods of pest and weed control.
Since outdoor pesticides and herbicides invariably end
up indoors on carpets and in the air, it is prudent to
reduce the use of chemicals indoors and out. Options
include integrated pest management, biological
pesticides, and planting disease-resistant plants.
If using chemicals, choose the least toxic. Look for
products with the signal word “warning” or “caution”
rather than “danger.” Baits and traps are better than
sprays or “bug bombs.”
Read the label and closely follow instructions. If you
must handle pesticides, wear gloves and long sleeves
and avoid breathing the vapors. Always keep these
chemicals away from children. Carefully follow
directions with regard to concentration, protective
gear, and restricting access to treated areas. Always
ventilate the area well after use, and mix or dilute
chemicals outdoors if possible.
Dispose of unwanted pesticides safely. Most of these
chemicals contain VOCs that will vaporize and get
into the household air. If you cannot dispose of partially
used containers, store outside the living space.
Minimize exposure to moth repellants. When used,
place mothballs, moth repellent cakes or moth crystals in a well-sealed trunk or other container that
can be stored in ventilated areas outside of the main
living space, such as attics or attached garages.
Minimize exposure to some air fresheners: Paradichlorobenzene is also the active ingredient in
many air fresheners and should be avoided.
Odors from pesticides or other chemicals applied in or around a building may be harmful, even fatal to building occupants. As with just about any chemical or substance, the hazard level depends on the dose and exposure, but as we discuss at ENDOCRINE DISRUPTERS at BUILDINGS even extremely low concentrations, as little as a single molecule of some substances can have very serious health effects depending on exposure conditions and who is being exposed.
Watch out: Be sure that the person selecting and applying pesticdes in or around your building is a properly trained, experienced, and licensed pest control operator.
In the 1980's we intercepted a newly-hired pest control operator who, standing under a literal rain of chlordane, was spraying both a wood-sided home in Poughkeepsie, NY (for carpenter ant control) and was about to soak the ground around the property's water supply well. We asked the operator if he was worried about being soaked with Chlordaine.
"Nah," he replied, "I've been doing this for three months now and I feel just fine."
While pesticide exposure studies may be performed on rats rather than human subjects, rats are little mammals; they're not pet rocks. It would be ridiculous to claim that a chemical that kills rats can be safely assumed to be harmless to humans, particularly to pre-natal and infants.(Barnett 1985).
Improper application of pesticides inside or even outside and around buildings and in building crawl spaces, attics or other areas can be far worse than ineffective against pests: it can be fatal for building occupants. In January 2017 four children died from breathing lethal gases that were generated when Weevil-Cide was sprayed under a home, then later tried to address a pesticide odor in the home by spraying water into the same area.
The result, reported by various sources including CNN and AcrossAmerica Patch (patch.com) was the production of a toxic gas that killed children in the home and left others very ill.
Bansal, S. K., S. R. Verma, A. K. Gupta, and R. C. Dalela. "Physiological dysfunction of the haemopoietic system in a fresh water teleost, Labeo rohita, following chronic chlordane exposure. Part I—Alterations in certain haematological parameters." Bulletin of environmental contamination and toxicology 22, no. 1 (1979): 666-673.
Barnett, John B., Benny L. Blaylock, Jay Gandy, Jay H. Menna, Richard Denton, and Lee SF Soderberg. "Long-term alteration of adult bone marrow colony formation by prenatal chlordane exposure." Fundamental and Applied Toxicology 14, no. 4 (1990): 688-695.
Barnett, John B., David Holcomb, Jay H. Menna, and Lee SF Soderberg. "The effect of prenatal chlordane exposure on specific anti-influenza cell-mediated immunity." Toxicology letters 25, no. 3 (1985): 229-238.
Cassidy, Richard A., Charles V. Vorhees, Daniel J. Minnema, and Lloyd Hastings. "The effects of chlordane exposure during pre-and postnatal periods at environmentally relevant levels on sex steroid-mediated behaviors and functions in the rat." Toxicology and applied pharmacology 126, no. 2 (1994): 326-337.
Holladay, Steven D., and Ralph J. Smialowicz. "Development of the murine and human immune system: differential effects of immunotoxicants depend on time of exposure." Environmental health perspectives 108, no. Suppl 3 (2000): 463.
McConnachie, P. R., and Arthur C. Zahalsky. "Immune alterations in humans exposed to the termiticide technical chlordane." Archives of Environmental Health: An International Journal 47, no. 4 (1992): 295-301.
Newsome, John and Shawn Nottingham, "4 Children die when pesticide, water mix creates toxic gas", CNN, 2 January 2017
Cantu, Tony, "Four Children Die in Amarillo After Inadvertently Inhaling Poisonous Gas" , Across America Patch, patch.com, 2 January 2017
Pesticide Odors [US EPA Web Page] U.S. EPA advice on pesticides and possible pesticide contamination.
Theus, S. A., D. R. Tabor, L. S. F. Soderberg, and J. B. Barnett. "Macrophage tumoricidal mechanisms are selectively altered by prenatal chlordane exposure." Inflammation Research 37, no. 1 (1992): 140-146.
Reader Question: How can we get rid of an annoying mothball odor in our Condo?
We moved into a condo, which is a concrete block structure 3 months ago. Shortly after the move we began to smell moth balls. After following the smell we were able to find out that the unit above us displaced several moth balls throughout there unit, tightly sealed the unit up without air conditioning on(we live in Florida) and left for the summer.
As the smell increased in our unit we begged parties involved to rid the unit of the moth balls and air it out.
Finally this was done, however even though the smell appears to be gone sometimes, other times we can still smell a bad odor, sometimes now the odor is less mothball smell and just simply a bad odor. We have tried everything and are desperate to solve the problem. Is it possible to get rid of this toxic odor? Any help would be greatly appreciated. - B.P. 9/22/2012
Reply: How to get rid of mothball odors in buildings, contents, clothing, furnishings
Indeed the odor from moth repellent products (paradichlorobenzene or naphthalene) penetrates many materials including even drywall and furnishings.
It can take quite a while for the smell to diminish.
at MOTHBALL ODORS we have included your question again in the FAQs section where we also have provided a detailed list of suggestions for getting rid of mothball odors, starting with ventilating the source area but adding other steps as well.
Please take a look at that article and let us know if questions remain.
The photo at left, though a white moth-like insect, is not a clothing-attacking moth, as you'll read at our mothball odor article.
Reader Question: my neighbour is spraying pesticide on my air conditioner
(Mar 29, 2013) Deborah So. CA said:
I am concerned that my psychopath neighbor is spraying a pesticide on my air conditioning unit. How can I test for this? Is there a city or county inspector I should seek out?
Contacting an environmental testing lab to confirm that you can use a sterile wipe (sterile cotton or swab) to wipe a representative surface for the lab to test. Discuss the common pesticides available in spray form and assure that the test will cover those chemicals. Typically you purchase one or several sterile swabs in sealed containers, use the swab, and return it to the test lab.
You might also set up a webcam to record activity.
You have the option of hiring a professional environmental test consultant but frankly, the cost - benefit sounds doubtful to me.
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Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education.
Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com
 Thomas M. Riddick, "Controlling Taste, Odor and Color With Free Residual Chlorination", Journal (American Water Works Association)
Vol. 43, No. 7 (JULY 1951), pp. 545-552, American Water Works Association, Article Stable URL: http://www.jstor.org/stable/41236445
 Douglas M. Baker, M.D., "Holiday Hazards", Pediatric Emergency Care, Vol. 1 No. 4, December 1985 Lippincott-Raven, retrieved 9/22/12
Abstract: Presented is a selective review of the toxicities of various plants, decorations, and miscellaneous items popularly used during the holiday season. Particularly hazardous agents include mistletoe, holly, bubble lights, fireplace flame colors, alkaline batteries, and mothballs. Specific questions regarding management of exposure to these items should be referred to regional poison control centers. Avoidance is the most effective treatment. ... [regarding mothballs, ... decontamination is advised for ingestions of greater than one half of a naphthalene mothball and more than two to three paradichlorobenzene mothballs ...]
 Charles M. McGinley, P.E., Michael A. McGinley, MHS, Donna L. McGinley, " “Odor Basics”,
Understanding and Using Odor Testing", paper presentation, The 22nd Annual Hawaii Water Environment Association Conference.,
Honolulu, Hawaii: 6-7 June 2000, St. Croix Sensory Inc. / McGinley Associates, P.A.
13701 - 30th Street Circle North
Stillwater, MN 55082 U.S.A.
firstname.lastname@example.org, retrieved 9/22/12, original source http://www.fivesenses.com/Documents/Library/33%20
%20Odor%20Basics.pdf, [copy on file as Odor_Basics.pdf]
 Jon H. Ruth, "Odor Thresholds and Irritation Levels of Several Chemical Substances: A Review", American Industrial Hygiene Association Journal
Volume 47, Issue 3, 1986, retrievedf 9/22/12, Abstract: A collation of odor threshold data for approximately 450 chemical substances is presented. The range of odor thresholds reported in the literature is shown along with any reported threshold of irritation to humans. These data can assist the industrial hygienist in determining when an “odor” may be in excess of the Threshold Limit Value®, when an organic vapor respirator is not acceptable due to the lack of an odor warning at the end of a cartridge life, and where odors may not indicate a hazard due to extremely low odor thresholds which may be well below the respective TLVs.
 Edward Avila DO,
Paul Schraeder MD,
Ajit Belliappa MD,
Scott Faro MD, "Pica With Paradichlorobenzene Mothball Ingestion Associated With Toxic Leukoencephalopathy", Journal of Neuroimaging
Volume 16, Issue 1, pages 78–81, January 2006, retrieved 9/22/12,
Abstract: This is a case report of central nervous system toxicity associated with paradichlorobenzene (PDCB) ingestion. The patient had ingested mothballs composed of 99.99% PDCB for a period of 7 months. She was admitted for depression and had no neurologic symptoms. Later she developed an acute cerebellar syndrome followed by stupor and coma. An extensive workup was negative except for decreasing levels of PDCB in her serum. Imaging revealed a diffuse leukoencephalopathy. Her clinical picture was attributed to PDCB toxicity.
 Stone, David L. (David Louis), Stock, T. (Tim), "Mothballs: proper use and alternative controls for clothes moths", PNW 606-E, May 2008, Oregon State University. Extension Service
Washington State University. Extension
University of Idaho. Extension, May, 2008, retrieved 9/22/12, original source: http://scholarsarchive.library.oregonstate.edu/
xmlui/bitstream/handle/1957/20800/pnw606-e.pdf?sequence=1, citation: http://hdl.handle.net/1957/20800, Abstract: In some homes, clothes moths can damage garments and other belongings. There are two common species of clothes moths in the Pacific Northwest: the webbing clothes moth (Tineola bisselliella) and the casemaking clothes moth (Tinea pellionella). The larvae, or immature form, of the moths are responsible for the damage done to personal belongings. [copy on file as Mothballs_Guide_PNW.pdf]
Citing the following 2 sources on mothball chemistry, use, hazards:
 Black, Judy. Fabric and Museum Pests. In
Mallis Handbook of Pest Control, 9th edition,
S.A. Hedges and D. Moreland, eds. GIE Media,
Cleveland, OH, 2004, pp. 581 –623.
 U.S. Department of Health and Human Services.
Illness Associated with Exposure to Naphthalene
in Mothballs—Indiana. Morbidity and Mortality
Weekly Report, 1983, Vol. 32: 34–5.
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