Sampling criteria for identifying human biomonitoring chemical differences in the Canadian Arctic

Figures & data

Table I. Demographic variables for mothers from the Inuvik Region of the Northwest Territories, and the Baffin Region of Nunavut

	Inuvik		Baffin
	Baseline study: 1998–1999	Follow-up study: 2005–2006	Baseline study: 1997	Follow-up study: 2005–2007
Age (years)
Mean (range)	25.6 (15–45)	25.3 (16–39)	25.3 (15–39)	24.1 (15–39)
Ethnicity
Inuit	32.6% (n=31)	68.4% (n=54)	88.6% (n=31)	100% (n=101)
Dene/Metis	44.2% (n=42)	24.1% (n=19)	N/A	N/A
Non-Aboriginal	23.2% (n=22)	7.6% (n=6)	11.4% (n=4)	N/A
Parity (No. of children)
1	40.4% (n=38)	36.7% (n=29)	34.3% (n=12)	21.8% (n=22)
2	24.5% (n=23)	22.8% (n=18)	14.3% (n=5)	23.8% (n=24)
3	19.1% (n=18)	12.7% (n=10)	17.1% (n=6)	24.8% (n=25)
4+	16.0% (n=15)	27.8% (n=22)	34.3% (n=12)	29.7% (n=30)

Table II. Percent decrease in geometric mean concentrations for PCB 153 and total mercury that can be detected for different sample sizes as the number of time periods increases (MSE=0.8757 for PCB 153; MSE=1.0422 for total mercury)

Log difference	% Decrease	Time periods	Sample size per period	Time periods	Sample size per period	Time periods	Sample size per period	Time periods	Sample size per period
PCB 153
0.10	10.5	2	345	3	283	4	240	5	210
0.15	16.2	2	154	3	127	4	108	5	94
0.20	22.1	2	87	3	72	4	61	5	54
0.30	35.0	2	40	3	33	4	28	5	25
0.40	49.2	2	23	3	19	4	16	5	15
0.50	64.9	2	15	3	13	4	11	5	10
0.60	82.2	2	11	3	9	4	8	5	7
0.70	101	2	9	3	7	4	6	5	6
0.80	123	2	7	3	6	4	5	5	5
0.90	146	2	6	3	5	4	5	5	4
1.00	172	2	5	3	5	4	4	5	4
Total mercury
0.10	10.5	2	410	3	336	4	286	5	250
0.15	16.2	2	183	3	150	4	128	5	112
0.20	22.1	2	104	3	85	4	72	5	64
0.30	35.0	2	47	3	39	4	33	5	29
0.40	49.2	2	27	3	22	4	19	5	17
0.50	64.9	2	18	3	15	4	13	5	11
0.60	82.2	2	13	3	11	4	9	5	8
0.70	101	2	10	3	8	4	7	5	7
0.80	123	2	8	3	7	4	6	5	5
0.90	146	2	7	3	6	4	5	5	5
1.00	172	2	6	3	5	4	4	5	4

Table III. Percent increase and decrease in geometric mean concentrations for PCB 153 and total mercury that can be detected when comparing 2 different groups of equal size (logsd=1.132 for PCB 153; logsd=1.203 for total mercury)

	PCB 153		Total mercury
Group sample size	% Decrease	% Increase	% Decrease	% Increase
10	62.9	170	65.2	187
15	55.5	125	57.7	137
20	50.4	102	52.6	111
30	43.6	77.4	45.6	83.8
40	39.1	64.3	41.0	69.4
50	35.8	55.9	37.6	60.2
60	33.3	50.0	35.0	53.8
70	31.3	45.5	32.9	49.0
80	29.6	42.0	31.1	45.2
90	28.2	39.2	29.6	42.1
100	26.9	36.9	28.4	39.6