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Concentration Adjustment

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Results on page last updated: 05/01/2024

Chemical Group: Polychlorinated Biphenyls (PCBs)

Measured in: Serum

Project: Biomonitoring Exposures Study (BEST) - 1.Pilot

Study Group: 112 adults
Sample Collection Date: 2011 - 2012

Unweighted Results

Chemical measured	Indicates Exposure to	Units	Number of people tested	Geometric mean	95% Confidence Interval		Selected Percentiles				Detection Frequency	Limit of Detection (LOD), wet-weight
Chemical measured	Indicates Exposure to	Units	Number of people tested	Geometric mean	Lower	Upper	25th	50th	75th	95th	Detection Frequency	Limit of Detection (LOD), wet-weight
PCB 118	PCB 118	ng/g lipid	110	4.84	4.10	5.71	2.43	4.14	8.48	19.8	96.4%	0.00800 ng/mL

Project: Biomonitoring Exposures Study (BEST) - 2.Expanded

Study Group: 341 adults
Sample Collection Date: 2013

Weighted Results

Chemical measured	Indicates Exposure to	Units	Number of people tested	Geometric mean	95% Confidence Interval		Selected Percentiles				Detection Frequency	Limit of Detection (LOD), wet-weight	Notes
Chemical measured	Indicates Exposure to	Units	Number of people tested	Geometric mean	Lower	Upper	25th	50th	75th	95th	Detection Frequency	Limit of Detection (LOD), wet-weight	Notes
PCB 118	PCB 118	ng/g lipid	217	2.85	2.34	3.46	1.29	2.52	4.78	13.4	77.5%	0.00800 ng/mL	♦

Project: California Childhood Leukemia Study (CCLS)

Study Group: 48 Mothers
Sample Collection Date: 2006 - 2007

Unweighted Results

Chemical measured	Indicates Exposure to	Units	Number of people tested	Geometric mean	95% Confidence Interval		Selected Percentiles				Detection Frequency	Limit of Detection (LOD), wet-weight
Chemical measured	Indicates Exposure to	Units	Number of people tested	Geometric mean	Lower	Upper	25th	50th	75th	90th	Detection Frequency	Limit of Detection (LOD), wet-weight
PCB 118	PCB 118	ng/g lipid	48	4.0	3.7	4.5	3.2	4.0	5.4	6.7	100%	0.010 ng/mL

Project: California Teachers Study (CTS)

Study Group: 2,869 female professional school employees
Sample Collection Date: 2011

Unweighted Results

Chemical measured	Indicates Exposure to	Units	Number of people tested	Geometric mean	95% Confidence Interval		Selected Percentiles				Detection Frequency	Limit of Detection (LOD), wet-weight
Chemical measured	Indicates Exposure to	Units	Number of people tested	Geometric mean	Lower	Upper	25th	50th	75th	95th	Detection Frequency	Limit of Detection (LOD), wet-weight
PCB 118	PCB 118	ng/g lipid	793	6.5	6.18	6.83	4.09	6.41	10.4	22	99%	0.015 ng/mL

Project: Firefighter Occupational Exposures (FOX) Project

Study Group: 101 Firefighters
Sample Collection Date: 2010 - 2011

Study Group Subset: Firefighters

Unweighted Results

Chemical measured	Indicates Exposure to	Units	Number of people tested	Geometric mean	95% Confidence Interval		Selected Percentiles				Detection Frequency	Limit of Detection (LOD), wet-weight
Chemical measured	Indicates Exposure to	Units	Number of people tested	Geometric mean	Lower	Upper	25th	50th	75th	95th	Detection Frequency	Limit of Detection (LOD), wet-weight
PCB 118	PCB 118	ng/g lipid	101	2.66	2.46	2.87	2.15	2.75	3.25	5.11	99.0%	0.006 ng/mL

Project: Maternal and Infant Environmental Exposure Project (MIEEP)

Study Group: 92 pregnant women and their infants (65 mother-infant pairs and 27 pregnant women)
Sample Collection Date: 2010 - 2011

Study Group Subset: Pregnant women

Unweighted Results

Chemical measured	Indicates Exposure to	Units	Number of people tested	Geometric mean	95% Confidence Interval		Selected Percentiles				Limit of Detection (LOD), wet-weight
Chemical measured	Indicates Exposure to	Units	Number of people tested	Geometric mean	Lower	Upper	25th	50th	75th	90th	Limit of Detection (LOD), wet-weight
PCB 118	PCB 118	ng/g lipid	77	*	*	*	<LOD	<LOD	2.02	2.97	0.014 ng/mL

Project: Measuring Analytes in Maternal Archived Samples (MAMAS) – MAMAS 1

Study Group: 460 pregnant individuals
Sample Collection Date: 2012

Study Group Subset: Subsample 1

Unweighted Results

1085d

Chemical measured	Indicates Exposure to	Units	Number of people tested	Geometric mean	95% Confidence Interval		Selected Percentiles				Detection Frequency	Limit of Detection (LOD), wet-weight
Chemical measured	Indicates Exposure to	Units	Number of people tested	Geometric mean	Lower	Upper	25th	50th	75th	90th	Detection Frequency	Limit of Detection (LOD), wet-weight
PCB 118	PCB 118	ng/g lipid	58	1.42	1.25	1.62	<LOD	1.54	2.08	2.59	69.0%	0.00705 ng/mL

Project: Measuring Analytes in Maternal Archived Samples (MAMAS) – MAMAS 2

Study Group: 540 pregnant individuals
Sample Collection Date: 2015 - 2016

Study Group Subset: Subsample 1

Unweighted Results

Chemical measured	Indicates Exposure to	Units	Number of people tested	Geometric mean	95% Confidence Interval		Selected Percentiles				Detection Frequency	Limit of Detection (LOD), wet-weight
Chemical measured	Indicates Exposure to	Units	Number of people tested	Geometric mean	Lower	Upper	25th	50th	75th	95th	Detection Frequency	Limit of Detection (LOD), wet-weight
PCB 118	PCB 118	ng/g lipid	242	*	*	*	<LOD	<LOD	<LOD	3.03	16.9%	0.0160 and 0.0180 ng/mL**

Project: Measuring Analytes in Maternal Archived Samples (MAMAS) – MAMAS 3

Study Group: 300 pregnant individuals
Sample Collection Date: 2016 - 2017

Study Group Subset: Subsample 1

Unweighted Results

Chemical measured	Indicates Exposure to	Units	Number of people tested	Geometric mean	95% Confidence Interval		Selected Percentiles				Detection Frequency	Limit of Detection (LOD), wet-weight
Chemical measured	Indicates Exposure to	Units	Number of people tested	Geometric mean	Lower	Upper	25th	50th	75th	95th	Detection Frequency	Limit of Detection (LOD), wet-weight
PCB 118	PCB 118	ng/g lipid	204	*	*	*	<LOD	<LOD	<LOD	<LOD	2.0%	0.0160 ng/mL

Footnotes

**LOD changed during the time that samples were analyzed for this project.

*Geometric mean was not calculated because the chemical was found in less than 65% of the study group

*Geometric mean was not calculated because the chemical was found in less than 65% of the study group.

♦Expanded BEST data from 217 participants was weighted, a statistical method to adjust over-represented and under-represented samples, so that the summary results adequately reflect the population of California’s Central Valley. Unweighted results are available to download on the Biomonitoring Exposures Study (BEST) – 2. Expanded project page.

Explanation of Terms

95% Confidence interval for the geometric mean

A 95% confidence interval for the geometric mean (CI-GM) is a range of values between two numbers called the lower bound and upper bound. These bounds are calculated based on sample data collected from a subset of a larger population. In repeated random sampling, the CI-GMs calculated for the various samples will contain the population value of the geometric mean 95 percent of the time. If convenience sampling is used to collect sample data, the CI-GM should be interpreted with caution. This is because a convenience sample may not be representative of the larger population.

95% Confidence interval for the geometric mean - lower

95% Confidence interval for the geometric mean - upper

Adjusted for

Chemical concentrations in urine can be adjusted for urine dilution using creatinine or specific-gravity. Chemical concentrations in serum can be adjusted for lipids. In the results tables, unadjusted chemical concentrations are denoted by NA.

Below the limit of detection (<LOD)

Below the limit of detection (< LOD) means that the laboratory could not detect the chemical. This may have been because the chemical was not present at all or because it was present at such a low level that the laboratory could not measure it.

Chemical measured

The chemical that was analyzed in blood or urine samples. The chemical measured is sometimes the parent chemical and sometimes a metabolite of the parent chemical.

Detection frequency (percent detected)

The percentage of study participants with a measurable level of a chemical in their blood or urine sample.

Geometric mean

The geometric mean is an estimated middle value of a set of numbers.This is different than the average, also called the "arithmetic mean". A geometric mean is sometimes calculated when the set of numbers contains some extreme values. For example, the geometric mean of the set of numbers "1, 2, 2, 3, 4, 5, 5, 6, 10, 100" is calculated by multiplying all ten numbers together and then raising to the 1/10th power, giving 4.8. To compare, the arithmetic mean is calculated by adding all ten numbers and dividing by 10, giving 14.

In the data tables, an asterisk (*) means the geometric mean was not calculated because the chemical was found in less than 65% of the study group.

Indicates exposure to

The chemical(s) listed in this column is the chemical(s) to which a person may have been exposed through various sources (e.g., via drinking water or use of a consumer product). This chemical is commonly called the parent chemical.

Limit of detection (LOD), wet-weight

The limit of detection (LOD) is the lowest level of a chemical that the laboratory can measure in whole blood, urine or serum. The wet-weight LOD is presented as an amount of a chemical per liter of a sample (for example, microgram of a chemical per liter of urine, or µg/L). This is often the way that biomonitoring results are reported as well (for example, µg/L urine or µg/L serum). In some cases, however, biomonitoring results are presented as lipid-adjusted concentrations (µg/g lipid) or creatinine-adjusted concentrations (µg/g creatinine). For these cases, the units for the wet-weight LOD will differ from the units used to report the biomonitoring results.

Number of people tested

The number of individuals whose blood or urine samples were analyzed for a particular chemical.

Sample collection date

The time period during which blood or urine samples were collected from participants in Biomonitoring California projects or laboratory collaborations.

Selected percentiles

A range of values calculated to show the distribution of measured chemical levels. See specific percentiles below for examples.

Selected percentiles - 25th

If the 25th percentile is 0.3 µg/L, for example, this means that 25% of participants had levels less than or equal to 0.3 µg/L.

Selected percentiles - 50th

If the 50th percentile is 0.6 µg/L, for example, this means that 50% of participants had levels less than or equal to 0.6 µg/L.

Selected percentiles - 75th

If the 75th percentile is 1.2 µg/L, for example, this means that 75% of participants had levels less than or equal to 1.2 µg/L.

Selected percentiles - 90th

If the 90th percentile is 1.5 µg/L, for example, this means that 90% of participants had levels less than or equal to 1.5 µg/L.

Selected percentiles - 95th

If the 95th percentile is 1.9 µg/L, for example, this means that 95% of participants had levels less than or equal to 1.9 µg/L.

Study group

A brief description of the people who provided blood and/or urine samples for analysis in a particular study.

Units

Human biomonitoring data are commonly reported as an amount of a chemical present in a specified volume of a bodily fluid (such as blood or urine). For example, a chemical measurement expressed in units of µg/L urine tells us the number of micrograms (µg) of the chemical present per one liter (L) of urine. Using standard units allows for comparison across different studies. For more examples, see definition for: Units used by Biomonitoring California.

Unweighted Results

Unweighted results summarize the measurements collected from study participants but may not apply to a wider group of Californians.

Weighted Results

Weighted results are results that have been calculated using a statistical method that adjusts over-represented and under-represented samples. Weighted results adequately reflect a wider population in California.

Results for Chemical Groups

Chemical Group: Polychlorinated Biphenyls (PCBs)

Project: Biomonitoring Exposures Study (BEST) - 1.Pilot

Unweighted Results

Project: Biomonitoring Exposures Study (BEST) - 2.Expanded

Weighted Results

Project: California Childhood Leukemia Study (CCLS)

Unweighted Results

Project: California Teachers Study (CTS)

Unweighted Results

Project: Firefighter Occupational Exposures (FOX) Project

Unweighted Results

Project: Maternal and Infant Environmental Exposure Project (MIEEP)

Unweighted Results

Project: Measuring Analytes in Maternal Archived Samples (MAMAS) – MAMAS 1

Unweighted Results

Project: Measuring Analytes in Maternal Archived Samples (MAMAS) – MAMAS 2

Unweighted Results

Project: Measuring Analytes in Maternal Archived Samples (MAMAS) – MAMAS 3

Unweighted Results

Footnotes

Explanation of Terms

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