How Accurate Are Lead Paint Test Kits

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Environ Res. Writer manuscript; available in PMC 2008 Jun 1.

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PMCID: PMC2170477

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Reliability of spot test kits for detecting lead in household dust

Katrina Smith Korfmacher

Environmental Health Sciences Center, 601 Elmwood Avenue, University of Rochester, Rochester, NY 14642

Sherry Dixon

National Center for Good for you Housing

Abstract

There has been a long-standing demand for a technique that can provide fast, accurate and precise results regarding the presence of hazardous levels of pb in settled house grit. Several abode testing kits are now bachelor. One kit manufactured past Hybrivet (LeadCheck Swabs) is advertised as able to observe lead dust levels that exceed the U.S. Environmental Protection Bureau's dust lead standard for floors (40 μg/ftⁱⁱ). The purpose of the study was to determine the ability of LeadCheck Swabs to instantly detect atomic number 82 in dust above EPA's gamble standard. A trained run a risk assessor collected 2 hundred LeadCheck Swab samples side-past-side with standard dust wipe samples. The effect of the LeadCheck Swab (positive (pink or red) or negative (yellow to brownish)) was compared with the laboratory results for the corresponding grit wipe (over or nether twoscore μg/ft²). The LeadCheck Swabs produced a false negative rate of 64% (95% confidence interval: 55%, 72%). The likelihood of a swab producing a false negative depended on substrate (painted or non-painted) and surface blazon (floor or sill). Changing the interpretation rule by classifying all swab colors except yellow as positive yielded lower faux negative rates nether some test conditions, but still produced high error rates. LeadCheck Swabs do not reliably detect levels of pb in grit above forty μg/ft² using published methods under field conditions. Farther research into alternate methodologies and interpretation guidance is needed to determine whether the swabs can be appropriately used by consumers and others to test homes for lead dust hazards.

Keywords: Pb chance assessment, Babyhood lead poisoning, Spot test kit, Pb grit, Lead testing

Introduction

In the past, the public'southward concerns nigh childhood atomic number 82 poisoning focused on children with high lead levels resulting from ingesting atomic number 82 based paint fries. Studies now show that lead grit from deteriorated lead-based paint and contaminated bare soil is the primary cause of elevated blood lead levels (Lanphear et al. 1998b; Bornschein et. al. 1987).

Children in homes with higher interior dust lead loadings are expected to have higher blood lead levels (Lanphear et al., 1998b; Lanphear et al., 1998c; Davies et al., 1990). Lanphear et al. showed that a child's claret atomic number 82 level was expected to be 14% college when the floor grit atomic number 82 loading was xl μg/ft² than when information technology was 20 μg/ft² (1998a).

Importantly, researchers have documented pregnant wellness impacts of childhood lead poisoning at lower blood lead levels (Canfield et al. 2003; Lanphear et al. 2000; CDC 1991). The recognition of threats posed by relatively low levels of household grit pb has increased the interest of resident and community groups and others in cheap methods for quickly and effectively determining the being of lead dust hazards in their homes.

The Alliance for Healthy Homes' Community Environmental Health Resource Eye (CEHRC) was the first wide scale program to help customs groups sample dust and soil for lead in high-hazard communities throughout the land (AFHH, 2006). As of 2005, community organizations had tested three,200 homes in xiii cities through the CEHRC initiative. This information has helped residents promote lead take a chance reduction both on a house-past-firm and community-wide basis.

The CEHRC program and similar efforts have relied on dust wipe sampling using the standardized techniques adopted past the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Housing and Urban Development (HUD). CEHRC trains community members in lead sampling for hazard identification (see EPA's July 2000 Lead Sampling Technician course and forty CFR Part 745 Subpart D, USEPA 2001). After these trained community members conduct a visual inspection, they collect dust lead samples on floors and windows in at least four rooms in each home, and mail them to an accredited lab for analysis.

While this procedure yields comprehensive and objective measurements of pb grit hazards in a dwelling, it has several drawbacks. Samplers must be carefully trained and supervised to maintain quality control and forbid contamination of samples. The laboratory report of dust lead levels is non immediately available, necessitating a second visit to the home to inform the occupant of the results. Although less expensive than professional take a chance assessments, which range from $300 to $600 per firm, the laboratory fees (effectually $vii per sample, or an average of around $60 per house) plus labor costs of the visual and dust wipe hazard assessment are prohibitive to many families and community groups.

Considering of these limitations, community-based organizations and others have actively searched for alternatives to accurately, immediately, and cheaply screen housing for atomic number 82 hazards. Spot lead test kits were initially developed to detect lead in paint and on consumer products such as glazed ceramics, jewelry and mini-blinds. Various types of inexpensive pb paint spot test kits have been available since the 1970's (NIST, 2000). Their accurateness is non regulated; withal, independent studies have been conducted to make up one's mind the accuracy of chemical spot tests for leaded paint (NIST, 2000).

The make of spot test kits used in this study, LeadCheck Swabs, has been produced by Hybrivet since 1991 for atomic number 82-based paint testing. This brand was called for this study because of its widespread availability and apply by community groups. The swab works past releasing a liquid containing rhodizonate ion from its tip, which turns pink or blood-red when reacting with lead. This color modify gives an immediate indication of the presence of lead. In quality control testing by the manufacturer, the chemic sensitivity of the LeadCheck Swabs was determined to be 2 micrograms of lead ion (Hybrivet, 1993). Chiefly, the Hybrivet website does non state whether the 2 microgram level refers to pb in solution or particulate matter. The Hybrivet spider web site states that the swabs are able to ″notice down to 2 micrograms of pb in defined laboratory testing, and reliably find 0.v% lead in paint with about 100% accuracy (within 95% Confidence limits)″ (Hybrivet, 2006). The website references third-party studies conducted past NIST (2000) and EPA (1995), amid others, as supporting its statements.

At the decision of most lead chance command interventions in federally assisted housing built earlier 1978, a certified risk assessor or lead sampling technician must verify that the lead gamble command work is complete and that the area is safe for residents, a process referred to every bit "clearance." Gamble assessors are required to comport a visual examination of the worksite to verify that all specified work is complete, that deteriorated atomic number 82-based paint (or deteriorated paint presumed to be lead-based paint) and lead-contaminated blank soil are satisfactorily controlled and that no visible settled dust or droppings remains. If the abode passes the initial visual exam, so the clearance examiner will collect dust wipe samples from the floor and window sill in at least four rooms of the dwelling, focusing especially on rooms where lead hazard command work was washed. . If the clearance examiner determines that the dwelling unit of measurement does not laissez passer the visual exam or if whatsoever dust sample has a dust lead loading at or higher up the applicable clearance standards (40 μg/ft² for floors, 250 μg/ftⁱⁱ for window sills, and 400 ug/ft² on window troughs), then the dwelling volition fail clearance and additional lead run a risk control piece of work must exist completed and/or the dwelling must be re-cleaned (U.Southward. EPA 2001).

CEHRC and other groups have adopted similar standards using visual and dust wipe assessments for take a chance identification under normal living atmospheric condition (not post-renovation). Still, given the costs of grit wipe testing, these groups accept sought less expensive methods for residents and customs members to detect hazardous levels of lead in dust.

LeadCheck Swabs concur widespread appeal for residents who want to know about dust lead hazards in their homes but cannot access or afford a total risk assessment or hazard screen. In a 2004 survey of county wellness departments in New York, one canton reported that it recommended LeadCheck Swabs to parents who called the wellness department with concerns about lead in their homes (Korfmacher KS unpublished data). Community groups in Cleveland (OH), Greensboro (NC), Hartford (CT), Indianapolis (IN), Los Angeles (CA), National City (CA), and San Francisco (CA), have used them to cheque pigment and/or grit and to educate residents about potential pb hazards. In early 2005, the Indiana State Department of Health bought more than than 50,000 LeadCheck Swabs to serve as a screening and educational tool to educate consumers, particularly new mothers bringing infants domicile from the infirmary.

LeadCheck Swabs accept appealed to community groups because they provide immediate results. They are likewise economical - when purchased in majority, single swabs cost around $1.thirty each. They are easily available in many retail outlets. Given the manufacturer's claims that they can detect lead in dust at levels equal to the EPA standard for floors, they may announced to be a helpful tool when dust wipes are not feasible due to resource constraints or when the delay in getting laboratory results is a problem. In addition, because a positive upshot of a habitation exam kit must exist disclosed by the property possessor to future tenants and/or buyers as office of lead chance disclosure, they may exist a useful tool for alerting owners and buyers to the potential run a risk from lead. According to the EPA and HUD, "if an owner has data obtained from the use of a abode exam kit for atomic number 82, that information must be disclosed; however, the owner should also disclose data about the reliability of the test kit" (USEPA 1996, p. 6).

Historically, the widespread utilise of spot test kits has been hampered past the failure to document acceptable sampling and analytical rates of error. Specifically, the kits may not be able to go lead into solution, where information technology can react with a colorimetric reagent, such as rhodizonate or sulfide, to produce a pink or black color, respectively. In the laboratory procedure, dust atomic number 82 wipe samples are typically treated with hot nitric and other strong acids to enable the atomic number 82 to enter solution. The solution is so typically analyzed by atomic absorption spectroscopy, ICP, or other procedure. Clearly, the utilize of hot strong acrid solutions in the dwelling environment poses its own hazards. If the spot examination kit fails to contact lead in a grade that causes the color reaction to occur, no observable colour alter tin occur and no lead will be detected, even if it nowadays.

In add-on, while community groups see smashing potential for spot test kits to aid in hazard identification, some professional risk assessors, public health officials, and others have expressed concerns nearly the potential of spot test kits to mislead consumers using them to screen for lead hazards. Some professionals accept expressed doubts that residents will know where to test or be able to use the exam kits properly. The colour change is subjective and may non exist observable to all, especially color-bullheaded individuals.

The primary business, however, is the risk of false negatives. That is, if a home test kit fails to detect an existing hazard, residents may believe that their homes are condom. Or, residents may behave renovation or remodeling activities that disturb pb-based paint thus generating even higher grit lead loadings. If spot test kits are to be used for dust pb take chances identification, they must have a very low rate of false negatives (high sensitivity).

A review of the peer-reviewed literature produced no studies evaluating the accuracy of the swabs and/or swab protocol under laboratory or field atmospheric condition in detecting dust pb levels above 40 μg/ft^two. Ane field study examined the effectiveness of the swabs in detecting grit lead levels above 200 μg/ft² (Pinto 1996). Hybrivet based their LeadCheck Swabs protocol for testing lead in dust on an extrapolation from this study. The research reported hither was conducted to address the lack of data on the effectiveness of LeadCheck Swabs to detect pb in dust at the EPA's standard for floors (forty μg/ft^two) using published methods nether field conditions.

Materials and methods

This study compared side-by-side samples using two different methods: LeadCheck Swabs and standard grit wipes. Dust wipe samples were nerveless by an EPA trained adventure assessor according to established methodologies (USEPA, 2001). Areas with visibly deteriorated paint or chips in the area to exist wiped were avoided. Grit wipes are generally taken over an surface area of one square foot. If this was not possible (for instance, on a window sill with a area less than one square human foot), the largest area possible was sampled while leaving room for a swab test on the aforementioned surface. Dust wipe analysis was conducted past a certified laboratory (Schneider Laboratories) using the EPA 7420 method utilizing flame atomic absorption spectroscopy, which reported results in micrograms per square human foot. The method detection limit of the laboratories was 20 μg/sample.

Field technicians were trained to use LeadCheck Swabs in accordance with protocols listed on the manufacturer'southward web site and in packaging materials. The technicians sampled an surface area of 2.7 × two.7 inches directly adjacent to the dust wipe sample area. On window sills, the swab sample was collected at i end of the sill. According to the manufacturer's instructions, the yellow swab would plow pink if lead loadings within this "palm sized area" exceed 40 μg/ftⁱⁱ. The resulting color of the swab was recorded as yellow, brownish yellow, yellow brownish, brown, or pink/red (come across Figure 2). If the swab yielded a negative issue (no clear pink colour), it was tested by squeezing some of the remaining fluid on a control leaded surface provided by the manufacturer as part of the kit to determine if the swab was defective (none were).

LeadCheck Swab color results

2a: Photograph of LeadCheck Swabs showing positive, negative, and inconclusive results.

2b: Inset: top view of dirty swab with pink visible backside tip

An boilerplate of 4 samples per firm were taken from a total of 50 pre-1978 homes, between June 2004 and March 2006 in Rochester New York as part of an ongoing atomic number 82 run a risk assessment program. Nigh of these homes were located in neighborhoods at loftier chance for pb hazards. Surface (floor or sill) and substrate (painted or unpainted) were recorded for each sample site. Approximately equal numbers of floors and sills were sampled to ensure a broad range of dust lead levels.

Two different rules were used for interpreting the color results of the swabs. Using a strict interpretation of the manufacturer's instructions, just those swabs that showed a distinctive pink or red colour were recorded as positive for atomic number 82 in dust hazards. Swabs with a brown tip but clear red colour backside the tip were also recorded as positive (see Figure 2, fourth sample from left, and inset showing top view of this sample). All other shades (yellow through brownish) were recorded every bit negative. An alternate interpretation was also used, nether which only those swabs that were clearly but yellowish were recorded every bit negative. All others (dark-brown yellow through pink/red) were recorded every bit positive.

Information were analyzed using SAS Version nine.i (Copyright © 2002-2003 by SAS Institute Inc., Cary, NC, U.s.). The ability of the swab upshot (positive or negative) to predict the dust wipe result (≥40 μg/ft² or <twoscore μg/ft²) was assessed with the sensitivity, specificity, negative predictive value, and positive predictive value. The sensitivity is the probability that the swab consequence is positive given that the grit wipe loading is ≥forty μg/ft^two. The false negative rate is 100% minus the sensitivity. The specificity is the probability that the swab consequence is negative given that the dust wipe loading is <40 μg/ft². The false positive rate is 100% minus the specificity. The positive predictive value (PPV) is the probability that the wipe effect is ≥40 μg/ft² given that the swab consequence is positive. The negative predictive value (NPV) is the probability that the wipe result is <40 μg/ft² given that the swab effect is negative.

The sensitivity, specificity, NPV and PPV were calculated for painted and unpainted surfaces, floors and windowsills and overall. Fisher's exact test was calculated with SAS procedure FREQ to test the hypothesis that there was a relationship between the swab upshot and the dust wipe result. Logistic models were created with SAS procedure GENMOD to determine if the probability of a positive grit swab effect depends on the dust wipe loading, substrate (painted or unpainted), and/or surface (floor or sill). Separate models were created for the standard and alternate swab interpretation rules. The post-obit three furnishings were included in each model:

• The dust wipe loading (μg/ft^two) (log-transformed to attain a normal distribution)

• An interaction term that immune the event of the dust wipe pb loading on the swab wipe issue to differ for painted and unpainted surfaces

• An interaction term that allowed the effect of the grit wipe lead loading on the swab result to differ for sills and floors

Results

The sensitivity and specificity of the LeadCheck Swabs was calculated for both the strict (manufacturer'southward) interpretation of the instructions and the alternating interpretation on different types of surfaces and substrates (Tables ​ 1 and ​ 2).

Tabular array ane

Performance of LeadCheck Swabs using the "standard" interpretation rule by surface and substrate type.

Surface	Substrate	Number of Samples	Percentage of wipes that exceed 40μg/ftii	Per centum of swabs that turn pink/scarlet)	Sensitivity (95% CI) (%)	PPV (95% CI) (%)	Specificity (95% CI) (%)	NPV (95% CI) (%)	Fisher's Exact Test P-value
Floors & Sills	All	200	60	23	36(28,45)	93(82,99)	96(xc,99)	51(42,59)	<0.001
	Painted	104	72	36	45(34,57)	92(78,98)	90(73,98)	39(27,51)	0.001
	Unpainted	96	46	9	xx(10,35)	100(66,100)	100(93,100)	60(49,70)	0.001
Floors	All	94	38	seven	xix(8,36)	100(59,100)	100(94,100)	67(56,76)	0.001
	Painted	29	59	21	35(14,62)	100(54,100)	100(74,100)	52(31,73)	0.028
	Unpainted	65	29	2	five(0,26)	100(3,100)	100(92,100)	72(59,82)	0.292
Sills	All	106	78	37	43(33,55)	92(79,98)	87(66,97)	30(xix,42)	0.007
	Painted	75	77	41	48(35,62)	90(74,98)	82(57,96)	32(19,48)	0.028
	Unpainted	31	81	26	32(15,54)	100(63,100)	100(54,100)	26(x,48)	0.298

Table ii

Performance of LeadCheck Swabs using the "alternate" interpretation rule by surface and substrate type.

Surface	Substrate	Number of Sample due south	Percent of wipes that exceed 40μg/ft2	Percent of swabs that turn chocolate-brown/ red*	Sensitivity (95% CI) (%)	PPV (95% CI) (%)	Specificity (95% CI) (%)	NPV (95% CI) (%)	Fisher's Exact Examination P-value
Floors & Sills	All	200	60	58	72(63,80)	74(65,82)	63(52,73)	61(49,71)	<0.001
	Painted	104	72	74	79(68,87)	77(66,86)	38(21,58)	41(22,61)	0.133
	Unpainted	96	46	41	61(45,76)	69(52,83)	77(63,87)	70(57,82)	<0.001
Floors	All	94	38	46	72(55,86)	sixty(44,75)	71(57,82)	eighty(67,90)	<0.001
	Painted	29	59	83	88(64,99)	63(41,81)	25(5,57)	sixty(15,95)	0.622
	Unpainted	65	29	29	58(33,fourscore)	58(33,eighty)	83(69,92)	83(69,92)	0.002
Sills	All	106	78	69	72(61,82)	82(71,90)	43(23,66)	30(16,49)	0.203
	Painted	75	77	71	76(63,86)	83(seventy,92)	47(23,72)	36(17,59)	0.079
	Unpainted	31	81	65	64(43,82)	80(56,94)	33(4,78)	18(2,52)	1.000

Under the strict interpretation, the overall sensitivity of LeadCheck Swabs was very low (36%). Interestingly, the sensitivity of swabs was higher on painted surfaces (45%) than on unpainted surfaces (twenty%). For both unpainted floors and sills, there was no clan between the swab issue and the grit wipe result (p=0.292 and p=0.298). The highest sensitivity is on painted sills (48%), the lowest on unpainted floors (5%). Overall, the swabs seem to do meliorate on sills than on floors. Dust atomic number 82 loadings tended to be college on sills, where 78% of the samples were above xl μg/ftⁱⁱ (geometric mean (GM) 206 μg/ft², geometric standard difference (GSD) 6.0), compared to 38% for floors (GM 41 μg/ft², GSD 5.5). Figure 3 presents per centum of positive, perhaps positive, and negative swabs past wipe dust pb loading. "Maybe positive" is defined as a swab result that is brown or a mix of brown and yellowish, which is positive nether the alternative interpretation but negative nether the standard interpretation. Effigy 3 shows that the swabs consistently performed better at college dust lead levels under the standard interpretation.

Percent of positive, possible positive, and negative swab results by dust wipe loading

The alternate interpretation, in which all not-yellow swabs are considered positive, is much more conservative. Not surprisingly, the alternate interpretation resulted in higher sensitivity overall. Nonetheless, there was no association between swab and wipe results for painted floors (p=0.622), painted sills (p=0.079) or unpainted sills (p=ane.0). A large percentage of floor samples (39%) resulted in some shade of brown color betwixt xanthous and pink and were therefore counted equally positive nether the alternate interpretation. Effigy 3 shows that the swabs did not consistently perform better at higher dust lead levels using the alternate interpretation.

The parameter estimates for significant variables from the models for both the standard and alternating interpretations are presented in Table 3. For the standard interpretation, the relationship between dust wipe loading and the swab effect is unlike for painted and unpainted surfaces (p=0.002), while controlling for location (floor or sill) and dust wipe loading. Swabs are more likely to be positive on painted surfaces than unpainted surfaces while controlling for dust wipe loading and location (i.e., flooring or sill). Furthermore, higher wipe loadings increase the odds of a positive swab more on painted surfaces than on unpainted surfaces. In improver, the relationship betwixt dust wipe loading and the swab result is different for floors and sills (p=0.016), while controlling for surface type and dust wipe loading. College wipe loadings increment the odds of a positive swab consequence more than on sills than on floors. In other words, while controlling for dust wipe loading levels and surface type (i.east., painted or unpainted), swabs are more likely to be positive on window sills than floors.

Table three

Parameter Estimates for Significant Variables in the Logistic Models to Predict the a Positive Swab Result

Parameter	Location	Surface Blazon	Standard Interpretation		Culling Estimation
			Approximate (Standard Error)	P-Value	Guess (Standard Error)	P-Value
Intercept	--	--	-5.199 (0.790)	<.001	-2.027 (0.454)	<.001
Log Grit Wipe Loading	--	--	0.665 (0.140)	<.001	0.4159 (0.107)	<0.001
Log Dust Wipe Loading * Location	Flooring	--	-0.203 (0.087)	0.019	--	--
Log Dust Wipe Loading * Surface Type	--	Painted	0.241 (0.079)	0.002	0.2459 (0.075)	0.001

The relationship between dust wipe loading and the swab result for the alternate interpretation does not differ past sampling location (p=0.379), while controlling for surface blazon and wipe loading. However, like to the standard interpretation, surface type (i.e. painted or unpainted) did bear on the relationship between dust wipe loading and the swab result (p<0.001). Higher wipe loadings increase the odds of a positive swab result more than on painted surfaces than on unpainted surfaces. That is, while decision-making for dust wipe loading, swabs are more likely to be positive on painted surfaces than unpainted surfaces.

Discussion

Overall, the rate of false negatives for the LeadCheck Swabs was 64% (sensitivity of 36%). Thus, nigh ii-thirds of the samples taking according to spot test kit instructions for detecting lead in dust and received a negative result, chancy levels of grit lead (i.e., ≥40 μg/ft²) were actually present.

At that place are a number of possible reasons why the LeadCheck Swabs did non perform as well every bit expected for detecting pb in grit nether field conditions. Outset, the number of chocolate-brown colored swab results suggests that dirt may interfere with the overall sensitivity of the swabs. Many of the swabs turned some shade of chocolate-brown between the pure yellowish and pink/red color results discussed in the LeadCheck Swab instructions. This suggests that household dirt may interfere with the reaction between the dye in the LeadCheck Swabs and reactive lead in the dust. Dust wipes are analyzed using flame atomic assimilation spectroscopy (FAAS), inductively coupled plasma emission spectrometry or other similar procedure, which detects total lead that has been dissolved and digested using strong acid and reflux, whereas the swabs may only detect free atomic number 82 ions that have been dissolved using the reagent in the swabs, which is not a strong acrid. Lead that is bound to other molecules or insoluble might non trigger the swabs' chemical reaction.

It should exist noted that the color change of the LeadCheck Swabs when exposed to insoluble salts of lead, such every bit atomic number 82 pyromorphite, lead chromate or lead sulfide, is unknown and not characterized past this study. Neither the standard method of digesting and analyzing lead dust wipe samples nor the swab method considers the effect of solubility or bioavailability (Cotter-Howells and Thornton 2005). However, it is noteworthy that grit wipe samples, which analyze full lead, have been shown to exist well correlated with children′s blood atomic number 82 level in both localized and nationwide studies, without controlling for speciation of lead salts (Lanphear et al. 1995; Wilson et al. 2006). Earlier whatever spot test kit for pb dust is considered to exist sufficiently reliable, the association betwixt the kit's event and children's blood lead levels should exist established.

Alternately, dirt on the swabs may brand it difficult to meet the true color change that resulted from the chemical reaction. That is, even if the reaction occurred the swab may appear to be brownish. The manufacturer's instructions practise not guide users in how to translate a brown color result on a swab (Figure 1); however, given the emphasis on a "red" or "pink" color, users are likely to consider a chocolate-brown swab to be negative for atomic number 82. Ane way to compensate for the uncertainties introduced past intermediate chocolate-brown color results is to employ the alternating interpretation rule for the LeadCheck Swabs' color result devised for this study. That is, the instructions could guide users to consider whatever swab that is not pure yellow to be "positive" for lead. Nether this alternate interpretation dominion, the fake negative rate drops to less than a third (28%). Using this more conservative approach to interpreting the color results of the LeadCheck Swabs could reduce false negatives greatly. However, the swabs' overall effective sensitivity is still simply 72% (95% CI: 63%, 80%) using the alternate estimation (Table ii), which is not advisable for a screening test to determine whether hazardous levels of lead are present in grit.

Directions for LeadCheck Swabs (from manufacturer'due south packaging insert)

It is also possible that dissimilar results in side-past-side swab and wipe samples may be a consequence of spatial variability in dust atomic number 82 levels or unlike sized areas being sampled. Although average dust lead levels over a square foot expanse may exceed 40 μg/ftⁱⁱ, the small sub-department of that area tested with the swab may have a lower dust lead level. The accepted protocol for dust wipes is to sample equally shut to ane square foot every bit possible. Previous studies have shown that wipe grit lead loadings from side-by-side samples on floors (areas of 1 ft²) and sills (areas of one/3 the sill) may vary substantially (Emond et al., 1998). This variation is likely to be amplified when using swabs, since the area inside a square with sides of 2.7 inches recommended in the LeadCheck Swabs protocol is around five% of a foursquare foot. Thus, one might await significant variance in results when the sampled areas are equally small every bit the swabbed areas. Notwithstanding, random variation in the spatial distribution of lead would be expected to consequence in more than disparate results, and not in consistently lower rates of positive results for wipes than swabs every bit was found in this report. Despite this spatial variability, the standard dust wipe procedure using the standardized surface area sizes has been shown to be significantly correlated with children's blood lead level (Lanphear et al. 1995; NCHH, 2004; Wilson, 2006).

For both the standard and alternative swab interpretations, swabs are more likely to be positive on painted surfaces than unpainted surfaces, while controlling for dust wipe loading. This could be due to the swab picking upwards lead from the painted surface or underlying layers of pigment if the acme layer is in poor status. If this is the example, the sensitivity of the swabs for dust may have been artificially inflated by reactions to underlying pigment, although it is unlikely the superlative glaze is lead-based paint. If so, the actual sensitivity of the LeadCheck Swabs for grit may be closer to the sensitivities calculated for not-painted surfaces, which are lower. Another possibility is that painted surfaces are smoother, assuasive the swabs to more than effectively pick up whatever dust on the surface than on a non-painted surface.

Although the standard of 40 μg/ft² does non use to window sills, this paper examined the functioning of the dust swabs on sills considering their inclusion allowed us to examine the swabs' performance over a larger range of dust pb loadings. Nosotros expected performance of the swabs on sills to be better than on floors due to higher dust pb loadings. Yet, this effect may have been kickoff by the higher variability in grit lead loadings on windowsills than floors (Emond et al., 1997). For the standard estimation, swabs were more probable to be positive on sills than floors even while decision-making for wipe dust lead loading and surface type (i.e., painted or unpainted). This difference could be attributable to poorer pigment condition on window sills than floors, exposing the swabs to lead paint in underlying paint layers. It could as well be due to different sources of lead dust on sills and floors.

Dust sampling was conducted for hazard identification in the homes in this study. Lead in dust at the time of hazard identification could come up from a variety of sources including friction, deterioration, and tracked-in dust or soil. In a clearance examination, the lead dust of concern is predominately from disturbance of lead-based pigment. Thus, inferences from these results should be express to take chances identification dust sampling, non clearance grit sampling. Floor dust lead loadings in the homes in this report were very high compared to the national averages (Jacobs et al., 2002). Thirty-eight percent of floor loadings were higher up 40 μg/ft² in this study, but only 8% of pre-1978 homes in the nation accept loadings in a higher place xl μg/ft² (USHUD, 2001). The overall simulated negative rate for LeadCheck Swabs in this study was 64%, just the false negative rates were lower at higher dust lead loadings. For wipe loadings more likely to exist observed under normal conditions in pre-1978 housing (betwixt 40 and 100 μg/ft²), the false negative rate was 85%. Thus, the swabs may accept really performed better in this report of high-risk housing than they would in average pre-1978 housing.

Conclusions

The results of this report suggest that LeadCheck Swabs do not reliably discover levels of lead in dust above 40 μg/ft^two using published methods under field weather. The swabs did not accurately predict chancy levels of dust pb loading for any studied surface (i.eastward., floors or sills) or substrate (i.due east., painted or unpainted).

Thorough enquiry needs to be conducted before LeadCheck Swabs or other spot examination kits should exist considered for clearance or hazard identification dust sampling. Time to come studies should explore the effects of the interference of dirt in the chemic reaction, a refined interpretation rule for the color results, and interference of underlying paint lead. Different lead sources (pigment, soil, etc.) should be tested to explore whether the swabs are more reliable in detecting certain kinds of lead, and whether the presence of pyromorphite significantly inflates the rate of false positives under field weather. The swabs should be validated over the appropriate range of dust lead levels and surface conditions (e.m. smooth and cleanable versus crude). Studies should too be based in a number of different cities due to regional differences in lead dust. Future studies should also consider swabbing larger areas, although the size of the area sampled may be limited by the quantity of reagent used in the spot exam kits. Ultimately, spot test kits should be field tested both past trained samplers and by untrained users typical of consumers (e.chiliad. residents and contractors) likely to use the product.

Guidance for the use of spot test kits for both grit and paint should clearly explain the risks of fake negatives and lay out appropriate follow-upwardly actions when negative results are accomplished. Given the low level of understanding of false negatives by many user groups and the high costs of imitation negatives in terms of risks to children'southward health, consumers may non exist able to accordingly apply and interpret the swabs without the support of trained staff who can offer advice and follow-upward testing.

ACKNOWLEDGEMENTS

The authors thank field staff Kate Kuholski, Deanne Mraz, Julie Rombaut, Steven Turner, and David Wilson equally well every bit David Jacobs, Jane Malone, Rebecca Morley, Tom Neltner, Ralph Scott, Marcia Stone and Emerge Thurston for comments on drafts of this newspaper.

FUNDING SOURCES

This research was supported by NIEHS grant number P30 ES01247 to the University of Rochester'southward Environmental Health Sciences Middle. The National Center for Healthy Housing provided funding for the statistical analysis and reporting.

Footnotes

Publisher'southward Disclaimer: This is a PDF file of an unedited manuscript that has been accustomed for publication. Every bit a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before information technology is published in its final citable form. Please note that during the production procedure errors may exist discovered which could affect the content, and all legal disclaimers that apply to the periodical pertain.

Human SUBJECTS/EXPERIMENTAL ANIMALS: none involved

Contributor Information

Katrina Smith Korfmacher, Environmental Health Sciences Center, 601 Elmwood Avenue, University of Rochester, Rochester, NY 14642 .

Sherry Dixon, National Heart for Healthy Housing .

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Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2170477/

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