Two Units Per Gram: The One Real Threshold in Structural Pest Control, and Why Nobody Measures It

1. Introduction: the exception we promised to look for

This journal's article on economic injury levels concluded that structural pest control has no usable action threshold, because the injury level for these pests is effectively zero and nothing sits below zero. It flagged one possible exception and said it deserved its own article. This is that article.

1.1 Why this is worth an article

Because as far as we can find, these are the only two numbers anywhere in structural pest control that attach a decision to a measurement. Everything else in this trade is professional judgement, regulatory zero, or a calendar.

2. What the threshold problem was

Restating it briefly for readers who have not read the earlier article.

An economic injury level is the pest density at which control costs less than the damage. An action threshold sits below it, so that you intervene before damage occurs. For structural and quarantine pests the injury level is effectively zero, one cockroach in a hotel being already unacceptable, so no threshold can sit below it.

2.1 The consequence we identified

No damage curve, no stopping rule, no basis on which to decline work or declare a programme finished. Which is why the recurring contract in our article on service economics has no exit condition.

2.2 What would fix it

A measurable quantity that varies continuously, has a documented relationship to harm, and responds to treatment. Sections 3 to 16 establish that cockroach allergen has all three, and §§17 to 19 explain why it still does not solve the problem.

3. The two numbers

Stated as they appear in the literature.

A review states that 2 U/g and 8 U/g of Bla g 1 or Bla g 2 have been considered thresholds of sensitization and asthma morbidity, respectively, for a long time.⁶

A national research institute describes them as 8.0 and 2.0 units of allergen per gram of dust, being the proposed thresholds for asthma morbidity and allergic sensitization, respectively.²

3.1 Two different endpoints

The lower number concerns becoming allergic. The higher concerns getting sick if you already are. They are not two points on one curve for one outcome, and conflating them is easy and wrong.

3.2 And two different populations

The sensitisation figure is about people who are currently not allergic and might become so, which means children, and means the number matters most in housing where children live and where exposure begins early.

The morbidity figure is about people who already are, and who will be at risk in any building carrying that load. One number is a prevention target and the other is a treatment target, and a service standard built on either would look different.

3.3 Which is more than any other structural pest has

This journal has written about bed bugs, rodents, cockroaches, ants, termites, flies and stored product insects. For none of the others did we find a published number attaching a decision to a measurement, and that absence is the subject of our injury level article.

4. Where the higher one came from

The provenance, which is a single large study.

A seminal study by Rosenstreich et al established 8 U/g of dust as threshold levels of morbidity due to asthma, as part of a National Cooperative Inner-City Asthma Study.¹

4.1 What that study reported

It found elevated concentrations of the cockroach allergen Bla g 1 in dust samples from 50.2 percent of the children's bedrooms. Of the children, 36.8 percent were allergic to cockroach allergen, 34.9 percent to dust-mite allergen, and 22.7 percent to cat allergen, while 50.2 percent had high levels of cockroach allergen in dust, 9.7 percent had high levels of dust-mite allergen, and 12.6 percent had high levels of cat allergen.³

4.2 The comparison that stands out

Sensitisation rates to cockroach and to mite were similar at 36.8 and 34.9 per cent. Exposure rates were not: 50.2 per cent for cockroach against 9.7 per cent for mite.³

In that housing stock, cockroach was the allergen people were actually meeting. Our article on dust mites and humidity explains one reason mite exposure can be low, and this journal has covered the cockroach side twice.

5. The two-condition structure

The logic the study tested, which is the part most often lost in summary.

For each allergen and measure of morbidity, the primary hypothesis we assessed was that morbidity due to asthma would be highest among children who were both sensitive to a given allergen and exposed to high levels of that allergen in their bedrooms.³

5.1 Sensitised and exposed

Both conditions. An exposed child who is not sensitised and a sensitised child who is not exposed are both outside the high-risk group.

5.2 Which has a direct operational consequence

The threshold is not a property of a building. It is a property of a building and its occupants together, and the same allergen concentration means something different in a household with no sensitised member.

That inference is ours, and it is the first of several reasons this number cannot simply be adopted as a service standard.

6. The plateau

A detail that complicates the lower number considerably.

Exposure to low doses of Bla g 1 (≤2 U/g of dust) was determined to be a risk factor for sensitization; however, the risk factor plateaus at greater than 4 U/g of dust.¹

6.1 Read carefully

Exposure at or below two units is a risk factor for sensitisation, and the risk stops increasing above four.¹

That is not a threshold below which you are safe. It is a curve that rises from a low exposure and flattens at a moderate one.

6.2 The implication for a reduction target

If the curve has already flattened above four units, then reducing a home from twenty units to five achieves nothing on the sensitisation endpoint, and reducing from five to one achieves most of what is available. That reading is ours and it is exactly the shape our dust mite article found in a different literature.

7. The unit problem

A measurement issue that a threshold cannot survive indefinitely.

The structure paper notes that the levels of Bla g 1 exposure in all these studies were expressed in arbitrary units and should be converted to absolute protein values to make comparable assessments of exposure.¹

7.1 Arbitrary units

Meaning defined by a reference preparation rather than by mass. Two laboratories using different reference material can report different numbers for the same dust.

This journal's article on detection probability made a related point about counts: a number is only a measurement if the thing being counted is defined. The same holds for a concentration.

8. The conversions disagree

And when the sources do convert, they do not agree.

The structure paper states that one arbitrary unit of Bla g 1 was calculated to be equivalent to 104 ng as absolute units, and describes the second allergen as having a similar equivalence of 80 ng per unit. On that basis, the threshold levels for risk of sensitization and asthma morbidity (2 and 8 U/g of dust, respectively) would be equivalent to 208 and 832 ng/g of dust for Bla g 1, comparable with levels of 160 and 640 ng per gram for the second allergen.¹

8.1 The other source gives half

A review states that 1 unit of Bla g 1 is equivalent to 0.1 µg and that 1 unit of Bla g 2 is equivalent to 0.04 µg.⁶

One hundred nanograms against one hundred and four is agreement. Forty nanograms against eighty is a factor of two.¹⁶

8.2 The practice parameter numbers

The same review reports that a cutoff of 0.04 µg/g dust for cockroach allergen Bla g 2 has been proposed as a threshold below which sensitization is prevented, and that levels greater than 0.08 µg/g have been associated with development of disease and symptoms.⁶

8.3 Which is a different ratio again

0.04 and 0.08 micrograms per gram is a factor of two between the two decision levels. Two and eight units per gram is a factor of four.⁶ We cannot reconcile these and we report them as they stand.

9. The second allergen is more potent

A fact that matters for which protein you would measure.

The second allergen has been reported to be very potent, inducing IgE sensitization at exposure levels that are 10- to 100-fold lower than those of other common indoor allergens, such as dust mite and cat.¹

9.1 Ten to a hundred times

Which is a large statement about relative potency and, if correct, means cockroach allergen occupies a different position from the mite allergen our previous article discussed.

9.2 The practical consequence

A building can hold a cockroach allergen burden well below what would matter for mite or cat allergen and still be a sensitising environment. Which means the intuition that a small infestation is a small exposure does not hold.

Our article on detection probability made the corresponding point about counts: a low trap catch is consistent with a population large enough to matter. Here a low allergen figure may be consistent with an exposure large enough to sensitise. That reading is ours.

10. How it is measured

The method, because a threshold is only as good as the assay under it.

In the national survey, dust samples were sieved through 425-μm pore grating, weighed, and divided into 100-mg aliquots of fine dust. Dust aliquots were extracted in borate-buffered saline and clarified by centrifugation. Supernatants were decanted and stored at -20°C. Cockroach allergen was measured by a two-site, monoclonal antibody enzyme-linked immunosorbent assay.⁵

10.1 The detection limit

The lower limit of detection of the assay varied and was 0.10 U/g for 94% of assayed samples, 0.20 U/g for 4%, and 0.40 U/g or 0.80 U/g for most others.⁵

A detection limit of 0.1 against a decision level of 2 gives a comfortable margin, which is more than can be said for most of the measurements in this journal's technology articles.

10.2 Concentration and load are different

Allergen loads are calculated as the product of concentration and dust weight, measured in units of allergen per square meter of sampled area.⁵

Concentration per gram of dust and quantity per square metre can move in opposite directions, and a thorough cleaning that removes dust changes both. This is a real ambiguity in what the threshold is a threshold on, and we have not seen it addressed.

11. What the national survey found

Prevalence in a nationally representative sample, which puts the numbers in context.

Cockroach allergen (Bla g 1) concentrations exceed 2.0 U/g, a level associated with allergic sensitization, in 11% of U.S. living room floors and 13% of kitchen floors. Concentrations exceed 8.0 U/g, a level associated with asthma morbidity, in 3% of living room floors and 10% of kitchen floors.⁵

11.1 The kitchen anomaly

Thirteen per cent of kitchen floors above the lower level and ten per cent above the higher one.⁵ The two figures are close, meaning that a kitchen which exceeds the lower level usually exceeds the higher one as well.

In living rooms the gap is wide, at eleven and three per cent. Our reading is that kitchens are either clean or badly contaminated with little in between, which is what you would expect if the source is a harbourage rather than diffuse deposition.

11.2 The housing associations

Elevated concentrations were observed in high-rise apartments, urban settings, pre-1940 constructions, and households with incomes < $20,000.⁵

Which reproduces the pattern our article on attached housing and our article on rental responsibility both described, from a nationally representative dust survey.

12. The link to cockroach numbers

The component that makes this a pest control threshold rather than only a medical one.

Odds of having concentrations > 8.0 U/g were greatest when roach problems were reported or observed and increased with the number of cockroaches observed and with indications of recent cockroach activity.⁵

12.1 A dose-response between pest density and allergen

More cockroaches, more allergen, in a nationally representative sample.⁵ That is the missing link between a count a technician can take and a health outcome a clinician cares about.

12.2 And it runs through observed activity, not just counts

The association was with roach problems reported or observed and with indications of recent activity, as well as with numbers.⁵ Which means the things a technician records on an inspection form are the things the allergen figure tracks, and this journal's article on trap catch interpretation is about how to read them.

12.3 Which is what an injury function looks like

Our economic injury level article described the missing element for structural pests as a damage curve relating density to harm. This is one, for one pest, with one health endpoint. That framing is ours.

13. The abatement trial

Whether the number responds to treatment, which is the last requirement.

The trial's stated background is that clinically relevant reductions in exposure to cockroach allergen, an important risk factor for asthma in inner-city households, have proven difficult to achieve in intervention trials, and its goal was to reduce mean Bla g 1 concentrations below the previously proposed thresholds for allergic sensitization and asthma morbidity.⁴

13.1 The design

A prerandomized, nonmasked trial with 16 intervention and 15 control homes was conducted. Study inclusion was based on 50 to 500 cockroaches trapped in a 3-day period. The interventions consisted of occupant education, placement of insecticide bait, and professional cleaning.⁴

13.2 The result

Bla g 1 concentrations in vacuumed dust were reduced by 96% on kitchen floors and 83% to 84% at the other sampled sites. Levels were reduced below the sensitization threshold (2 U/g) in beds, arguably the most relevant site for exposure, and below the asthma morbidity threshold (8 U/g) on bedroom floors and living room floors/sofas.⁴

14. What that trial actually did

The composition of the intervention deserves attention.

Education, bait and professional cleaning.⁴ Two of those three are not pest control as the trade practises it.

14.1 The cleaning is doing work

Because the allergen is a protein in settled dust, and removing dust removes protein regardless of whether any insect dies. A commercial source states the point bluntly: killing cockroaches doesn't eliminate existing allergens.⁷

14.2 The entry criterion is the interesting part

Fifty to five hundred cockroaches trapped in three days.⁴ A trap count used as an eligibility gate, which is the sort of quantified entry condition this journal's article on trap catch interpretation argued the trade should use.

15. The trial that compared two pest control models

A study design we found while researching this and did not expect.

In a research institute's intervention study, treatment-1 homes will receive exterminations by university staff at baseline and then as needed, as determined by cockroach trap counts, while treatment-2 homes will receive extermination by commercial applicators according to the terms of the contract.²

The stated comparison is that the percentage of homes for which concentrations are reduced below 8.0 and 2.0 units of allergen per gram of dust will be compared between groups.²

15.1 Read the two arms again

Treatment as determined by trap counts, against treatment according to the terms of a contract.²

15.2 The monitoring is common to both

Both arms were monitored the same way, with traps set and dust sampled periodically in all homes.² Only the intervention rule differed, which is the correct design for isolating what the rule contributes.

16. Why that design matters

Because it is a direct test of the thing our service economics article said had never been tested.

That article observed that the central empirical question about the recurring contract, whether scheduled service beats measurement-driven intervention, appears never to have been examined. This trial's two arms are exactly that comparison, with allergen concentration as the endpoint.

16.1 What we do not have

The result. The page we read describes a study that is closed to recruitment and sets out the planned analysis; we did not locate the published outcome.²

16.2 Which is frustrating and worth recording

A threshold-driven arm against a contract-driven arm, with a validated objective endpoint, in real housing. If that comparison has been published, it is the single most relevant piece of evidence in this trade and we could not find it.

17. The objection that undoes it

And here the case collapses, in one sentence from a recent review.

However, there is evidence supporting a dose-response relationship between exposure and sensitization or disease, rather than the existence of specific thresholds.⁶

17.1 What that means

That two and eight are conventions marking points on a continuous curve, not step changes in risk. Below two is lower risk, not no risk.

The plateau finding in §6 points the same way, from the other end.¹

17.2 So the problem from our earlier article reappears

The economic injury level for these pests was effectively zero because any detected presence constituted damage. A dose-response with no lower bound says the same thing in epidemiological language: there is no exposure level at which risk becomes zero, only levels at which it becomes small.

That is our reading and it is the central argument of this article.

18. What a dose-response means operationally

Being constructive about it, because a dose-response is not useless.

A threshold answers the question of whether to act. A dose-response answers the question of how much benefit a given reduction buys, which is a better question and a harder one.

18.1 The recommendation the practice parameter gives instead

Bla g 1 levels greater than 0.1 µg/g dust or Bla g 2 levels greater than 0.04 µg/g have indicated an increased likelihood that there are sources of cockroach allergen production; therefore, it has been recommended that Bla g 1 levels ideally should be reduced to less than twice these levels.⁶

18.2 That is a target, not a threshold

Reduce to below a stated figure, because above it there is probably a source producing allergen.⁶ Which is a diagnostic use of the number rather than a decision rule, and it is defensible in a way the threshold framing is not.

18.3 And the strongest recommendation is not a number at all

Elimination of cockroaches carried out through an integrated pest management and removal of reservoirs of cockroach contaminants were the strongest recommendations to decrease cockroach exposure and reduce asthma morbidity.⁶

Note both halves. Eliminate the insects, and remove what they left behind.

19. The threshold is on the wrong object

The structural problem with adopting this as a pest control standard.

It measures a protein in dust. Pest control kills insects. Those are different quantities with different dynamics, and the protein persists after the insects are gone.⁷

19.1 Which means a perfect treatment can fail the test

Eliminate every cockroach in a unit and the settled allergen remains until somebody removes it. A programme evaluated against the allergen number would be scored as failing while having achieved complete pest control.

19.2 And an imperfect one can pass

Thorough cleaning without effective treatment reduces the measured quantity while leaving the source producing more. A commercial source states that standard cleaning isn't enough and that without specialised approaches levels remain well above thresholds,⁷ which is a claim from a company selling a specialised approach and should be read that way.

19.3 The trial in §13 did both

Bait and professional cleaning together.⁴ That is the correct response to §19.1 and §19.2, and it is not what a standard pest control contract contains.

20. Which splits the service in two

The same split our service economics article proposed, arriving here from the health side.

That article argued that a recurring contract bundles surveillance and application, and that they should be priced and justified separately. This literature adds a third component that belongs to neither: allergen removal.

20.1 Three products

Find it. Trap counts and inspection, which relate to the source.

Kill it. Bait and treatment, which reduce production.

Remove what it left. Cleaning, which reduces the standing quantity and is the part the trade does not sell.

20.2 Only the third moves the health endpoint directly

Which is our inference from §19 and from the composition of the trial intervention.⁴ It also matches what our articles on allergen intervention trials found: the successful interventions were multifaceted and the cleaning component was always present.

21. Does it qualify as an action threshold

The verdict, component by component.

Every structural requirement is met. A measurable quantity, a validated assay with an adequate detection limit, stated decision levels, a documented relationship to pest density, and a demonstrated response to intervention.⁵⁴

21.1 And it fails anyway

Because the thing it measures is not the pest, because the relationship is continuous rather than stepped, because the units are arbitrary and their conversions conflict, and because nobody in this trade samples dust.⁶¹

21.2 The honest summary

This is the closest structural pest control gets to an evidence-based stopping rule, and it comes from a different profession, measures a different quantity, and is currently being abandoned as a threshold by the people who proposed it.

22. What would have to change

Because the gap is not unbridgeable.

Standardise the units. Absolute protein mass rather than arbitrary units, which the structure paper explicitly calls for.¹

Decide what the measurement is on. Concentration per gram of dust or quantity per square metre, since cleaning moves them differently.⁵

Publish the comparison in §15. Threshold-driven against contract-driven, with an objective endpoint.²

And make sampling affordable. A dust sample and an assay is not a large cost against the price of a year of service, and no current service model includes it.

22.1 The one that could happen tomorrow

The last of those. Vacuumed dust from a defined area, sieved and assayed, is routine laboratory work,⁵ and a pest control programme in a household with diagnosed cockroach allergy is exactly the case where a before-and-after measurement would tell everybody something they currently guess at.

That would not resolve the threshold question in §17. It would replace a judgement with a number, which is the more modest and more achievable goal.

23. The Manitoba position

The usual answer.

We found no cockroach allergen measurements from Manitoba housing, no local sensitisation prevalence data and no indication that dust sampling is performed anywhere in this province outside a research setting.

23.1 And one reason it might differ here

The American survey's associations were with housing type and income rather than with climate, so there is no obvious reason the pattern would not hold in comparable Winnipeg housing.⁵ But the species mix, the heating season and the ventilation regime all differ, and none of those has been checked.

23.2 Why it would be worth having

The national survey found elevated concentrations associated with high-rise apartments, urban settings and pre-1940 construction.⁵ Winnipeg has all three in quantity, and this journal's first article was about exactly that housing type.

This is the third article in which we have identified the same missing measurement. It is a dust sample and a laboratory assay.

24. Our own position

The disclosure and the practical consequence.

We are a pest control contractor. We do not measure allergen, we do not offer allergen removal, and the standard service we sell addresses the source rather than the residue.

24.1 What we take from this literature

That in a household with a diagnosed cockroach allergy, the job is not finished when the cockroaches are dead. The protein is still there, it is what makes people ill, and somebody has to remove it.⁶⁴

Saying so, and saying that it is a cleaning task rather than a treatment task, is the honest position even though it points work away from us.

24.2 And what a client in that situation should ask

Whether the plan addresses the residue as well as the insects, and if not, who is doing that part. A contractor who has not thought about the question is answering only half of it.

25. Limitations and open questions

We are not clinicians. This article reports an evolving position in allergy medicine and does not adjudicate it.⁶

Two sources are commercial. A company selling allergen removal products and a consumer blog, both flagged, and both used only for claims we could corroborate or for statements we then qualified.⁷⁸

One striking figure we could not verify. Both commercial sources report that early exposure at or above two units per gram produces a relative risk for incident asthma of approximately 36, against roughly 8 at lower exposures. Neither gives a primary citation we could follow, and a relative risk of that magnitude is unusual enough that we report it only as an unverified claim appearing in two secondary sources.⁷⁸

Several papers were read as abstracts. The abatement trial and the structure paper in particular, so effect sizes, confidence intervals and methodological detail are not available to us.⁴¹

The conversions are unresolved. Section 8 reports a factor of two discrepancy between sources on one allergen and we could not determine which is current.¹⁶

The study in §15 may have published results we did not find. Our search located the study description only.²

All the data is American. Housing stock, cockroach species prevalence and socioeconomic distribution all differ, and none of it was collected here.⁵

Sections 1.1, 2.2, 3.1, 5.2, 6.2, 7.1, 10.2, 11.1, 12.2, 14, 16, 17.2, 18.2, 19, 20, 21, 22 and 24 are our reasoning. The claim that these are the only numeric thresholds in the field, the reading of the two-condition structure, the plateau argument, the concentration versus load ambiguity, the kitchen distribution reading, the injury function argument, the assessment of the two-arm trial design, the wrong-object argument, the three-product split and the practical recommendations are ours rather than sourced positions.

26. Conclusion

Two units of cockroach allergen per gram of settled dust for sensitisation, eight for asthma morbidity, in use as thresholds for a long time and established in an inner-city asthma study.⁶¹ A validated monoclonal assay with a detection limit twenty times below the lower figure. A nationally representative survey finding 13 per cent of kitchen floors above it. Odds of exceeding the higher level rising with the number of cockroaches observed. And a randomised trial cutting concentrations by 96 per cent on kitchen floors using education, bait and professional cleaning.⁵⁴

That is every component of the action threshold this journal said structural pest control does not have. It is also, on the current expert reading, not a threshold. The evidence supports a dose-response between exposure and sensitisation or disease rather than specific levels,⁶ the sensitisation risk is reported to plateau above four units so that large reductions in badly contaminated homes may buy nothing,¹ the units are arbitrary and two reputable sources differ by a factor of two on what one of them weighs.¹⁶

And the number is on the wrong object. It measures a protein that outlives the insect producing it, so a complete kill can fail the test and a thorough clean can pass it while the source keeps working. The practice parameter's strongest recommendation is accordingly not a number but a pair of actions: eliminate the cockroaches through integrated pest management, and remove the reservoirs of what they left behind.⁶ This trade sells the first and not the second, which means that in the one case where a measurable health endpoint exists, the standard service is structurally incapable of meeting it.

References

1. The novel structure of the cockroach allergen Bla g 1 has implications for allergenicity and exposure assessment. Journal article in an allergy and clinical immunology title, read as abstract and article extract. Used for the statement that sensitization to cockroach allergens is a major risk factor for asthma and that the fold and biological function of the protein were unknown; for the report that exposure to low doses at or below 2 units per gram of dust was determined to be a risk factor for sensitization but that the risk factor plateaus above 4 units per gram; for the attribution of the 8 units per gram morbidity threshold to a named seminal study forming part of a national cooperative inner-city asthma study; for the observation that exposure levels in these studies were expressed in arbitrary units and should be converted to absolute protein values to make comparable assessments; for the calculated equivalences of one arbitrary unit of Bla g 1 to 104 nanograms and of the second allergen to 80 nanograms per unit; for the resulting conversions of the 2 and 8 unit thresholds to 208 and 832 nanograms per gram for the first allergen, described as comparable with 160 and 640 nanograms per gram for the second; and for the report that the second allergen is very potent, inducing IgE sensitization at exposure levels 10 to 100-fold lower than other common indoor allergens such as dust mite and cat. https://www.jacionline.org/article/S0091-6749(13)00982-2/fulltext
2. Cockroach Allergen Intervention. National environmental health research institute study description page for a closed study. Used for the statement that the most important risk factor for asthma in inner-city homes may be exposure to cockroach allergen; for the described protocol in which staff periodically administer a questionnaire, set cockroach traps to monitor numbers and sample dust to monitor allergen levels, with dust analysed for two named cockroach allergens; for the two intervention arms, namely homes receiving extermination by university staff at baseline and then as needed as determined by cockroach trap counts, and homes receiving extermination by commercial applicators according to the terms of the contract; and for the planned analysis comparing the percentage of homes for which concentrations are reduced below 8.0 and 2.0 units of allergen per gram of dust, described as the proposed thresholds for asthma morbidity and allergic sensitization respectively. https://www.niehs.nih.gov/research/atniehs/labs/crb/studies/closed-studies/cockroach
3. The Role of Cockroach Allergy and Exposure to Cockroach Allergen in Causing Morbidity among Inner-City Children with Asthma. Journal article in a general medical title, read as abstract and article extract. Used for the finding of elevated concentrations of the named cockroach allergen in dust samples from 50.2 per cent of the children's bedrooms; for the reported figures that 36.8 per cent of children were allergic to cockroach allergen, 34.9 per cent to dust-mite allergen and 22.7 per cent to cat allergen, while 50.2 per cent of bedrooms had high cockroach allergen levels, 9.7 per cent high dust-mite levels and 12.6 per cent high cat levels; for the statement of the primary hypothesis that morbidity due to asthma would be highest among children both sensitive to a given allergen and exposed to high levels of it in their bedrooms, with high exposure defined according to proposed thresholds for causing disease; for the method of measuring major allergens of cockroach, dust mite and cat in household dust using monoclonal antibody based enzyme-linked immunosorbent assays; and for the supporting observations that other studies found high levels of the second cockroach allergen in 37 to 85 per cent of urban homes, that sensitivity to cockroach allergen is found in 23 to 60 per cent of urban residents with asthma, and that allergic persons with asthma have acute episodes when exposed in bronchial provocation tests. https://www.nejm.org/doi/full/10.1056/NEJM199705083361904
4. Abatement of cockroach allergen in low-income, urban housing: a randomized controlled trial. Journal article in an allergy and clinical immunology title, read as abstract. Used for the background statement that clinically relevant reductions in exposure to cockroach allergen have proven difficult to achieve in intervention trials; for the stated goal of reducing mean concentrations below the previously proposed thresholds for allergic sensitization and asthma morbidity; for the design as a prerandomized, non-masked trial with 16 intervention and 15 control homes, with study inclusion based on 50 to 500 cockroaches trapped in a three-day period, and interventions consisting of occupant education, placement of insecticide bait and professional cleaning; and for the results that concentrations in vacuumed dust were reduced by 96 per cent on kitchen floors and 83 to 84 per cent at other sampled sites, with levels reduced below the sensitization threshold of 2 units per gram in beds, described as arguably the most relevant site for exposure, and below the asthma morbidity threshold of 8 units per gram on bedroom floors and living room floors and sofas. https://www.sciencedirect.com/science/article/abs/pii/S0091674903014635
5. National Prevalence and Exposure Risk for Cockroach Allergen in U.S. Households. Open-access journal article reporting a nationally representative survey. Used for the findings that concentrations of the named allergen exceed 2.0 units per gram, a level associated with allergic sensitization, in 11 per cent of living room floors and 13 per cent of kitchen floors, and exceed 8.0 units per gram, a level associated with asthma morbidity, in 3 per cent of living room floors and 10 per cent of kitchen floors; for the observation that elevated concentrations were seen in high-rise apartments, urban settings, pre-1940 constructions and households with incomes below twenty thousand dollars; for the finding that odds of concentrations above 8.0 units per gram were greatest when roach problems were reported or observed and increased with the number of cockroaches observed and with indications of recent activity; for the laboratory method in which dust samples were sieved through 425 micron pore grating, weighed and divided into 100 milligram aliquots of fine dust, extracted in borate-buffered saline, clarified by centrifugation and stored at minus twenty degrees, with allergen measured by a two-site monoclonal antibody enzyme-linked immunosorbent assay; for the reported detection limits of 0.10 units per gram for 94 per cent of assayed samples, 0.20 for 4 per cent and 0.40 or 0.80 for most others; and for the distinction that allergen loads are calculated as the product of concentration and dust weight, measured per square metre of sampled area. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1440774/
6. Review article on indoor allergen exposure and asthma, open-access. Used for the statement that in addition to evidence of cockroach presence by visual inspection or sticky trap placement, measurement of allergen levels could be useful to guide environmental interventions; for the practice parameter positions reported in it, namely that a cutoff of 0.04 micrograms per gram of dust for the second cockroach allergen has been proposed as a threshold below which sensitization is prevented and that levels greater than 0.08 micrograms per gram have been associated with development of disease and symptoms; for the statement that 2 units per gram and 8 units per gram of either named allergen have been considered thresholds of sensitization and asthma morbidity respectively for a long time, with one unit of the first equivalent to 0.1 micrograms and one unit of the second to 0.04 micrograms; for the qualification that there is evidence supporting a dose-response relationship between exposure and sensitization or disease rather than the existence of specific thresholds; for the recommendation that levels above stated figures indicate an increased likelihood of sources of allergen production and that levels ideally should be reduced to less than twice those figures; and for the statement that elimination of cockroaches through integrated pest management together with removal of reservoirs of cockroach contaminants were the strongest recommendations to decrease exposure and reduce asthma morbidity. https://pmc.ncbi.nlm.nih.gov/articles/PMC5575827
7. Cockroach allergen guide, retailer of allergen-reduction products. Commercial source with a direct interest in the conclusion that cleaning alone is insufficient, cited as attributed material and treated with corresponding caution. Used for the claims that regular vacuuming and surface cleaning can remove some allergens but that without specialised approaches levels remain well above the thresholds associated with sensitization and asthma morbidity; that killing cockroaches does not eliminate existing allergens while surface cleaning misses airborne particles; and for the reported but unverified figure that early exposure at or above 2 units per gram creates a relative risk for incident asthma of approximately 36. https://allergydefender.com/pages/bla-g-1-and-bla-g-2-understanding-the-proteins-behind-cockroach-allergies
8. Consumer guide page on cockroaches and allergy. Commercial consumer website, cited as attributed material and treated with corresponding caution. Used only for the reported but unverified dose figures that home concentrations between 0.05 and below 2 units per gram raise incident asthma risk approximately eight-fold while concentrations at or above 2 units per gram raise it approximately 36-fold, figures which corroborate those in the preceding reference without either source giving a primary citation we could follow; and for the statement that kitchen floors and cabinet surfaces carry the greatest levels of the first named allergen. https://cockroaches.homes/do-cockroaches-spread-allergies-and-asthma/