Spot Test Kits for Detecting Lead in Household Paint: A Laboratory Evaluation.
Spot Test Kits for Detecting Lead in Household Paint: A
Laboratory Evaluation.
(1559 K)
Rossiter, W. J., Jr.; Vangel, M. G.; McKnight, M. E.;
Dewalt, G.
NISTIR 6398; 94 p. May 2000.
Sponsor:
Department of Housing and Urban Development, Washington,
DC
Available from:
National Technical Information Service
(NTIS), Technology Administration, U.S. Department of
Commerce, Springfield, VA 22161.
Telephone:
1-800-553-6847 or 703-605-6000;
Fax: 703-605-6900; Rush
Service (Telephone Orders Only) 800-553-6847;
Website:
http://www.ntis.gov
Order number: PB2000-100134
Keywords:
paints; detection; kit response; lead based paint; lead
level; lead chromate; operator effect; spot test kits;
testing; white lead
Abstract:
A laboratory study was conducted to determine the
reliability of spot test kits for detecting the presence
of lead in household paint when tests were conducted by
certified lead inspectors or risk assessors. Reagent
solutions were applied to paint specimens and,
subsequently, the specimens were observed for
characteristic color change. For the study, four test
kits were based on the reaction of lead ion with sulfide
ion to produce a gray or black color, whereas four
others were based on the reaction of lead ion with
rhodizonate ion to give a pink or red color. These eight
kits were used in an experiment investigating the effect
of lead level, lead pigment type, operator, paint-film
substrate, overlayer paint type, and overlayer paint
thickness. Test samples, prepared using either a white
lead (i.e., basic lead carbonate) or a lead chromate
pigment, had ten lead levels ranging from 0 mg/cm2 to
3.5 mg/cm2. Five operators were trained according to
test protocols based on each kit manufacturer's
instructions. The study showed that the spot test kits
gave positive results at lead levels less than 1 mg/cm2.
Consequently, a positive response could not be relied on
to indicate the presence of lead-based paint, which is
defined as paint having lead levels equal to, or greater
than, 1 mg/cm2. This finding is consistent with the
results of past field studies. A criterion against which
a spot test kit may be considered as acceptable for use
as a negative screen (i.e., a test for which a negative
result indicates a low probability of lead > 1 mg/cm2)
for the presence of lead-based paint was proposed. This
criterion is: Upon evaluation of spot test kit response,
the probability of a negative response (with 95%
confidence) at a lead level of 1 mg/cm2 is < 5%.
Equivalently, the lead level at which there is a 95%
probability of a positive response (with 95% confidence)
should be < 1 mg/cm2. The type of lead pigment had a
significant effect on the spot test kit response. For
white lead specimens, six kits--three sulfide-based and
three rhodizonate-based--gave low percents of false
negatives (< 2%) and met the proposed criterion for
acceptance as a negative screen for lead-based paint.
For lead chromate specimens, three of these six kits
(two sulfide-based and one rhodizonate-based) also had
low percents of false negatives (< 2%) and met the
proposed acceptance criterion. The other
factors--overlayer type, overlayer thickness, operator,
and substrate--did not generally show significant
effects in cases where the spot test kits appeared to be
candidates for use as negative screens for lead-based
paint. Finally, the study results lead to the suggestion
that an evaluation of spot test kit response should
afford a low percent of positive results at the 0 mg/cm2
lead level because, in practice, false-positives may
needlessly spur test kit users into taking further, but
unnecessary, investigative action for the presence of
lead.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899