Assessing background particulate contamination in an historic building – surface lead loading and contamination

Figures & data

Table 1. Sample zones.

Zone	N Samples	Description	Area ft^2
Background	15	Undisturbed office areas on third floor with no recent demolition	15,000
A	10	Planned renovation on second floor area in which no demolition had occurred	1500
B	15	Uncontrolled demolition in basement	10,000
C	15	Uncontrolled demolition on second floor prior to general contractor arriving on site	8500
D	10	Ground Level office – moderate cleaning	2500

Table 2. Example data randomly selected from Building zone C (serving as the control) and the Background zone (suspect).

Zone	Lead ug/ft^2
Control	190	390	650	1500	750	1900	870
Suspect	3300	1900	24,000	2100	190	1500	380

Table 3. Randomization/permutation calculation of significance based upon example data; probability values for Δf_d equal to or greater than exhibited in the data are bolded/italicized.

Detection Freq	→		0	1	2	3	4	5	6	7
↓	Rel Freq		0.0000	0.1429	0.2857	0.4286	0.5714	0.7143	0.8571	1.0000
		Probability	0.00781	0.05469	0.16406	0.27344	0.27344	0.16406	0.05469	0.00781
0	0.0000	0.00781	–	–	–	0.00214	0.00214	0.00128	0.00043	0.00006
1	0.1429	0.05469	–	–	–	–	0.01495	0.00897	0.00299	0.00043
2	0.2857	0.16406	–	–	–	–	–	0.02692	0.00897	0.00128
3	0.4286	0.27344	–	–	–	–	–	–	0.01495	0.00214
4	0.5714	0.27344	–	–	–	–	–	–	–	0.00214
5	0.7143	0.16406	–	–	–	–	–	–	–	–
6	0.8571	0.05469	–	–	–	–	–	–	–	–
7	1.0000	0.00781	–	–	–	–	–	–	–	–

Table 4. Lead surface data from five (5) zones within the building.

Zone	Lead ug/ft^2
Background	3400	49	1600	1000	240	240	3300	2100	3900	380
	190	1500	2600	24,000	1900
A	640	0	57	110	48	270	62	510	21,000	1800
B	790	1600	760	980	820	120	730	590	400	1800
	1900	190	890	770	2000
C	860	650	190	750	4200	1500	870	920	1300	1100
	1900	13,000	2200	1200	390
D	0	0	0	14	0	2400	120	260	180	170

Table 5. Comparison of lead surface loading across various zones using N/P vs. permutation/randomization inference.

Key: Ref: Reference lead surface loading (ug/ft^2) for comparison; frequently the median of the combined data f (CZ)/N: frequency lead >/ = reference lead surface loading in Control Zone/No. Samples f(TZ)/N: frequency lead>/ = reference lead surface loading in Test Zone/No. Samples p B > A: probability lead surface loading in Test Zone is greater than in Control Zone
			Permutation/Randomization			N/P Statistical Inference
Control Zone (CZ)	Test Zone (TZ)	Ref ug/ft^2	f(CZ)/N	f(TZ)/N	pTZ>CZ	Mean ug/ft^2	Statistic
A	Background	640	2/10	10/15	0.99	Mean A = 2449.7 Mean Background = 3093.27	t means = 0.2554 MW = 1.969
A	C	860	2/10	11/15	0.99	Mean A = 2449.7 Mean C = 2068.67	t means N/A MW = 2.413
C	Background	1550	4/15	8/15	0.90	Mean C = 2068.67 Mean Background = 3093.27	t means = 0.5906 MW = 0.3940
B	C	840	6/15	11/15	0.95	Mean B = 956.0 Mean C = 2068.67	t means = 1.334 MW = 1.244
D	Background	260	1/10	11/15	1.00	Mean D = 314.4 Mean Background = 3093.27	t means 1.466 MW = 3.190
B	Background	2050	0/15	6/15	0.99^1	Mean B = 956.0 Mean Background = 3093.27	t means = 1.391 MW = 1.307

¹In this instance, the greatest difference in detection frequency occurs at 2050 ug/ft² rather than the combined median of 935 ug/ft². At the combined median, pTZ>CZ = 0.95.