Cockroaches: An Indoor Air Problem

What cockroaches are
Where cockroaches are found
Health problems associated with cockroaches
Decreasing exposure to cockroaches

What Cockroaches Are

Cockroaches are a type of insect that is considered an indoor pest. Around the world, there are about 5,000 different species of cockroaches; most species of cockroaches live in the tropics. The world's largest roach is six inches long with a one-foot wingspan and lives in South America. Pest cockroaches are native to western Asia and northern Africa and were carried all over the world in wooden ships. Sir Francis Drake once captured a ship that was overrun with millions of roaches. Now they are found everywhere, even the North and South Poles. Thankfully, just a few species are considered pests and live in homes. The most common cockroach in US homes is the German cockroach.

Where Cockroaches Are Found

Cockroaches may be found in homes that have four things that make them thrive:

• A food source

• Adequate humidity levels

• Warmth

• Places to hide, such as cracks and crevices

Cockroaches are not picky eaters and feed on things such as various foods, paints, wallpaper pastes and book binding. Cockroaches have been known to go without eating for a month; however, they will only live a week without water.

In homes, cockroaches are most likely to be found in kitchen cabinets, kitchen floor dust, bathrooms, and basements. Though cockroaches can be found in all types of homes, they are most likely to be found in the homes of poorer people. A cockroach expert at the US Department of Agriculture actually counted all the German cockroaches in about 1,000 low-income apartments in Gainesville, Florida. The average number of cockroaches was 13,000 per apartment.¹

Health Problems Associated with Cockroaches

Many people who are allergic to house dust are also allergic to cockroaches. Cockroaches may cause allergies resulting in skin rashes, allergic reactions, and asthma. Primarily it is the cockroach's feces, saliva, eggs, and outer covering left behind on surfaces that contain substances that people are allergic to. It has been shown that the incidence of asthma and allergies is greater in people continually exposed to cockroach infestations. Data from one study showed that 7.5 percent of 253 normal people showed allergic skin responses to extracts of cockroaches while 28 percent of 114 allergic people were affected.² Another study found that up to 60 percent of people with asthma tested positive to cockroach allergen.³ Asthmatic children who are allergic to cockroaches are three times more likely to be hospitalized for their asthma if they live in a house with a large cockroach population.³ Allergens present in the feces of the German cockroach can become airborne along with normal house dust. The allergens can then be inhaled from the air or ingested when in contact with food.

The National Cooperative Inner City Asthma Study set out to find why asthma was so severe and common in poor neighborhoods. They researched this problem in the worst neighborhoods in seven big cities. They assumed that the dust mite would be the leading cause of asthma as it is in the suburbs, but that was not the case. Instead, they found that cockroaches were the leading cause of asthma in the 1,528 children under the age of 10 who they studied. They found sky-high levels of cockroach feces in the kitchens, bathrooms, and even the beds.¹

Another problem with cockroaches is that they may carry disease-causing bacteria and fungi that may contaminate food. Cockroaches have been found to be the cause of Salmonella food poisoning that can be life-threatening. Bacteria such as Staphylococcus, Streptococcus, coliforms and other bacterial pathogens have also been found in cockroaches. This is because after feeding on contaminated food, disease bacteria can remain in the cockroach digestive system for a month or more. Later, human food or utensils can become contaminated with cockroach feces. It has been shown that Salmonella bacteria survive in cockroach feces for several years.⁴

Decreasing Exposure to Cockroaches

• Cleanliness and removal of food sources are critical to minimizing roach populations.

• Keep opened food (cereals, pasta and crackers to name several examples) in airtight jars and plastic containers.

• Clean dishes nightly, or, if you do not, be sure they are sitting in a basin of soapy water.

• Keep counters, sinks and tables clean and clear of clutter.

• Fix plumbing leaks and other moisture problems.

• Take piles of boxes, newspapers, and other items where cockroaches may hide out of your home.

• Make sure trash in your home is properly stored in containers with lids that close securely, and remove trash daily.

• Do not leave pet food out overnight.

• Clean all cabinets (especially under the sink) and then place bay leaves in them as well as the pantry, cupboards and shelves to repel cockroaches.

• Put a light sprinkling of boric acid along the back and sides of cabinets, under the refrigerator, and into cracks and other places where roaches hide. Roaches will avoid piles of boric acid, so use a fine dusting. This is a proven, less-toxic roach control product. Conventional pesticides kill bugs quickly, but they contribute to poor indoor air quality and are more toxic. Still, be careful using boric acidas it can be dangerous if it is eaten, so only apply it in out-of-the-way places where pets and children cannot touch it. Keep it away from places where they may get to it, such as on the floor.

• Apply a fine dusting of diatomaceous earth or silica gel to roach walkways. These dusts dehydrate and repel roaches.

• Throw away anything old, moldy or wet, such as rags and sponges.

• Keep brushes and sponges in plastic tubs (you can make cleaning caddies from cut-away milk jugs) so they do not touch the floor.

• Clean up spills under the sink right away.

• Clean behind the refrigerator and wash the drip pan beneath it.

• In apartments, neighbors should do the cleaning and boric acid routine at the same time to be effective.

Close openings into the house (for example, gaps around pipes and electrical work, door molding and cracks in walls) with caulking, screening and/or weather-stripping as appropriate. Cockroaches can crawl into some astonishingly small spaces. Young roaches need only a crevice 0.5 mm wide or a space as thin as a dime. Adult males can squeeze into a space of 1.6 mm or the thickness of a quarter. Pregnant females need the most space of all to hide: 4.5 mm or a space as wide as two stacked nickels.

References

1. Haney DQ. Roaches top cause of asthma among the poor. Palm Beach Post. June 9, 1996.

2. Luft P. All about cockroaches. Biohaven Insect Resources. 1996: www.biohaven.com/pests/roach/roachinf.htm. Date accessed, October 2000.

3. Jones AP. Asthma and domestic air quality. Soc. Sci Med. 1998;47(6):755-764.

4. University of Nebraska. Cockroach Control Manual, Chapter 1. 2000: www.ianr.unl.edu/ianr/pat/chapter1.htm. Date accessed October 2000.