Environmental Engineering Reference
In-Depth Information
were adjusted for the number of persons in the household (which would re
ect the
average inter-use stagnation time).
The EU Report also states that the
protocol should give a realistic estimate of
the problems in the area, in order to be able to use it as an effective decision tool.
Furthermore, the result should not unnecessarily worry consumers
“
”
(EU Report,
p. 46). While it is legitimate not to
(the case of
false positives), there is also a need to minimize the possibility that a sampling
protocol would indicate a value less than 10
“
unnecessarily worry consumers
”
µ
g/L when the measuring device value
shows a value greater than the MCL of 10
µ
g/L (false negatives). For a property
identi
ed as a false negative, the consumer believes that his/her drinking water is
safe and no action needs to be taken; although he/she will be ingesting unsafe levels
of lead each day. On the other hand, with false positives the consumer will be
attempting to improve his/her plumbing system but will probably continue to
consume
“
safer
”
drinking water in the future since the COMP has a value less than
the MCL of 10
g/L. The EU Report has failed to address and analyze the issue of
false negatives adequately and has focused its attention on false positives. Fur-
thermore, for the properties which were identi
µ
ed as false positives (sampling lead
value > COMP value when in fact COMP < the sampling lead value), the lead
concentration from the COMP sampler was very close to the value of 10
µ
g/L; on
average the COMP estimate for lead for false positives was between 6 to 10
µ
g/L
which is very close to surpassing the MCL value of 10
µ
g/L (see Fig. 26, EU
Report, p. 48). Since 80 percent of the properties that were
had lead
plumbing, they were potentially problem properties to begin with. An examination
of Fig. 25, which shows the number of false negatives for each sampling protocol,
indicates that the number of households with lead over the 10
'
false positives
'
g/L is fairly high
and is comparable to the number of false positives. For the 30MS and average of
RDT and FF, a rough calculation from graphical inspection only shows that
approximately 8 percent of households are false negatives, for RDT approximately
4 percent and for FF approximately 15 percent.
“
µ
was based on hypothetical or assumed wage rates, average travel time
between properties, time needed by sampler to perform procedure, analysis costs,
and write off cost of sampling device. The average time for RDT and FF is much
lower than that of 30MS as well as the measured lead from the device as a sampling
procedure. The
Cost
”
several aspects
of the procedure (e.g. is the procedure easily applicable, are skilled samplers nee-
ded, does the procedure need speci
“
practicality
”
of a sampling protocol was based on
“
c tools
…
)
”
(EU Report, p. 56).
“
Consumer
acceptance
”
although a
“
very important factor
”
(EU Report, p. 57) according to the
Report was not well de
ned. The brief description given for this assessment type is
that consumer acceptance was based on consumer
'
s willingness to cooperate and
“
if
”
the sampling procedure bothers the consumers too much
(EU Report, p. 57). Both
practicality and consumer acceptance had no quanti
able evaluation scheme in the
Report. However, qualitative results were given. In terms of practicality, cost-
effectiveness, and consumer acceptance, the 30MS scored the lowest (worst) of all
tested protocols while the RDT scored the highest (best) followed by the FF
sampler. RDT had the least cost followed by FF, followed by the 30MS. Lastly, the
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