Tag Archives: Bomb

German cockroach.

Bug bombs don’t kill the bugs, but they do expose you to pesticides

Bug bombs are really good — if you like having cockroaches for flatmates.

Orion insecticide.

Orion insecticide.
Image credits Tamorlan / Wikimedia.

New research from the North Carolina State University showed that total release foggers (commonly known as “bug bombs”) are ineffective at removing cockroaches from your home. The chemicals they release fail to reach the places that these insects tend to hang out in, such as the undersides of surfaces or inside cabinets.

Indiscriminate bombing

“There’s been a general assumption that bug bombs work to eliminate cockroaches indoors, but no one had conducted a formal assessment of their efficacy and any exposure risks,” said Zachary DeVries, an NC State postdoctoral researcher and the lead author of the study.

“We’ve done that simultaneously in this study.”

Besides not removing the majority of cockroaches, these devices also leave behind toxic residues — particularly in the center areas of floors and furniture. Cockroaches tend to avoid these areas, but they see heavy use by humans and pets.

The team tested four different commercially-available bug bombs that use various insecticide compounds in five apartment complexes. These complexes were chosen for their level of bug activity — all five had moderate to severe German cockroach (Blattella germanica) infestations. All the bombs used in the study contained pyrethroids, the team explains, a class of fast-acting insecticides. Some also contained other active substances, such as piperonyl butoxide, which prevents cockroaches’ bodies from metabolizing the insecticides.

German cockroach.

German cockroach, Blattella germanica.
Image credits Matt Bertone.

First, they estimated cockroach populations in 20 homes in these five complexes. Then, following the instructions on their labels to the letter, the team set up and set off the bombs. Cockroach populations were re-examined two weeks and one month after the bombs were used. Overall, these devices had no meaningful impact on the insects, the team finding no evidence of decline from their initial estimates.

“The bug-bomb products did absolutely nothing to control cockroach populations in these homes,” DeVries said.

The team also applied either commercially-available gel bait or a professional-grade gel bait in 10 additional homes. Gel bait is generally applied via a syringe to the areas where cockroaches hide. This bait was much more effective than the bug bombs both at the two- and four-week marks, the team notes, virtually eliminating cockroach populations in all of the 10 homes.

To help them better gauge the effectiveness of the bug bombs, the team placed roaches (some raised in the lab and others captured into the homes themselves) in cages on the floor and in upper cabinets of the homes involved in the study. The cages were greased so that the insects couldn’t escape. These cages were installed during the bug bomb testing phase of the study.

“The lab roaches, which are not hardy, had high mortality, as expected,” DeVries explains. “The roaches captured in the homes and then brought back, however, had far lower mortality rates than you would expect from direct exposure to bug bombs, confirming the ineffectiveness of these products when used for German cockroach control.”

Overall, then, the bug bombs had shown themselves ineffective in their intended role. With this in mind, the team set out to quantify their collateral effect — the risk of exposing people and pets to insecticides in their homes. The team swabbed floors, kitchen surfaces, walls, and cabinets in the homes prior to bug-bombing them. This preliminary analysis showed insecticide residue was already present in the homes used in the study, giving the team baseline concentrations to work with. These baseline levels can be explained by residents facing cockroach infestations — as was the case with the families involved in the study — using insecticides in an attempt to remove the pests. These residues were found in samples collected from the middle of floors and kitchen surfaces, DeVries explains, so the finding is “most disconcerting”.

The same areas were swabbed four to six hours after the bombs were deployed. The team reports that insecticide residue levels increased 600-fold on average across all horizontal surfaces. Swabbings performed one month after the study showed insecticide residue levels were still 34% higher than the baseline.

“Bug bombs are not killing cockroaches; they’re putting pesticides in places where the cockroaches aren’t; they’re not putting pesticides in places where cockroaches are and they’re increasing pesticide levels in the home,” DeVries said. “In a cost-benefit analysis, you’re getting all costs and no benefits.”

“This is of particular concern in low-income communities, where bug bombs are frequently used because professional pest control may be too expensive,” adds Coby Schal, Blanton J. Whitmire Distinguished Professor of Entomology at NC State and senior author of the paper.

Insecticides aren’t particularly healthy for you — by ‘particularly’ I mean ‘at all’. Pyrethroids, the same compounds used in this study, are preferred for household use due to their fast biodegradation/breakdown and relative low mammalian toxicity (except for cats) compared to other insecticides.  However, there is evidence that even pyrethroids have an adverse effect on the development of rats, causing behavioral changes that resemble Attention Deficit/Hyperactivity Disorders (ADHD) in humans. There have also been reported cases of anaphylactic shock after exposure to pyrethrum, although no link between pyrethroids and allergic reactions has so far been established in the scientific literature.

The paper “Exposure risks and ineffectiveness of total release foggers (TRFs) used for cockroach control in residential settings” has been published in the journal BMC Public Health.


Bombs dropped during the Second World War were felt to the edge of space

The Second World War brought unprecedented destruction upon the face of the Earth — one that reached up to the edge of space, new research reveals.


Image via Pixabay.

Allied bombing raids during the Second World War caused shockwaves so strong that they weakened the ionosphere, the electrified layer of the atmosphere that reaches up to 1000 km (621 mi) above ground, reports a new paper from the University of Reading.

High-altitude bombing

“The images of neighbourhoods across Europe reduced to rubble due to wartime air raids are a lasting reminder of the destruction that can be caused by man-made explosions,” says Chris Scott, Professor of Space and Atmospheric Physics at Reading and one of the paper’s coauthors. “But the impact of these bombs way up in the Earth’s atmosphere has never been realised until now.”

“It is astonishing to see how the ripples caused by man-made explosions can affect the edge of space. Each raid released the energy of at least 300 lightning strikes. The sheer power involved has allowed us to quantify how events on the Earth’s surface can also affect the ionosphere.”

World War Two was perhaps the single most calamitous war humanity has ever embarked upon. Fueled by an already-ripened Industrial Revolution and incredible technological leaps, belligerent countries unleashed unprecedented destruction upon their foes’ troops and homelands.

So awesome was their fury that not even the ionosphere escaped unscathed. The team drew on daily records collected by the Radio Research Center in Sough, UK, between 1943-45, a period that saw rapid development of radio and radio-based technology (such as radar). Among other research topics, scientists at the center shot sequences of shortwave radio pulses at heights between 100 and 300 km (62 to 186 mi) above the Earth’s surface in order to better understand the height and ionization levels of layers within the upper atmosphere.

Their work helped reveal the existence of the ionosphere — and now, it’s helping researchers understand how natural forces from below, like lightning, volcanic eruptions, or earthquakes, affect this layer of our atmosphere.

The ionosphere underpins several technologies such as radio communications, GPS systems, radio telescopes, and some variations of radar, as it helps bounce radio signals back down towards the surface (instead of letting them escape to outer space). So it’s not hard to see why we want to have as comprehensive an understanding of it as possible. Being a highly-charged layer, the ionosphere is strongly influenced by solar activity.

However, scientific modeling has revealed that our star alone cannot account for all the waxing and waning we see in this layer. Ground-level activity has to account for the rest.

Higher-altitude effects

To help us understand how ground-level events influence this layer, the team studied the ionosphere’s response around the time of 152 large Allied air raids in Europe.

The team focused on Allied bombing runs over continental Europe rather than attacks more close to the center — such as the infamous London ‘Blitz’ — due to their more sporadic nature. The Blitz was a monumental and sustained bombing effort, but its continuous nature (and the fact that relatively little information is available to accurately time and locate individual runs) made it much more difficult for the team to tease out its effects from natural, seasonal variations in the ionosphere. In other words, Nazi Germany dropped so many bombs on Britain and for so long, that it ruined the data sample.

Another factor that made the team focus on Allied raids was sheer ‘boom’. The German Luftwaffe employed two-engine tactical bombers, which carried relatively small bombs; the Allies, in contrast, relied on four-engine strategic bombers that carried much larger ordinance — such as the 10-tonne ‘earthquake bomb’ Grand Slam. Quantity, it turns out, truly is a quality in and of itself:

“Aircrew involved in the raids reported having their aircraft damaged by the bomb shockwaves, despite being above the recommended height,” says Professor Patrick Major, University of Reading historian and a co-author of the study. “Residents under the bombs would routinely recall being thrown through the air by the pressure waves of air mines exploding, and window casements and doors would be blown off their hinges.”

“There were even rumours that wrapping wet towels around the face might save those in shelters from having their lungs collapsed by blast waves, which would leave victims otherwise externally untouched.”

The team reports that electron concentration in the ionosphere dropped significantly following these events, due to shockwaves generated by air-detonating bombs exploding near the surface. These pressure waves, the team believes, heated up the upper atmosphere, enhancing the loss of ionization.

“The unprecedented power of these attacks has proved useful for scientists to gauge the impact such events can have hundreds of kilometres above the Earth, in addition to the devastation they caused on the ground.”

The researchers now need members of the public to help digitize more early atmospheric data, to understand the impact of the many hundreds of smaller bombing raids during the war, and help determine the minimum explosive energy required to trigger a detectable response in the ionosphere.

The paper has been published in the journal Annales Geophysicae.