Table of Contents

Component Description

Phthalates are a group of chemicals used to make plastics more flexible and harder to break. They are often called plasticizers. Some phthalates are used as solvents (dissolving agents) for other materials. They are used in many products, such as vinyl flooring, adhesives, detergents, lubricating oils, automotive plastics, plastic clothes (raincoats), and personal-care products (soaps, shampoos, hair sprays, and nail polishes). Phthalates are used widely in polyvinyl chloride plastics, which are used to make products such as plastic packaging film and sheets, garden hoses, inflatable toys, blood-storage containers, and medical tubing. 1,2-Cyclohexane dicarboxylic acid, diisononyl ester (DINCH) is used as a replacement of some high molecular weight phthalates. Once phthalates or DINCH enter a person's body, they are converted into breakdown products (metabolites) that pass out quickly in urine. Biomeasures of phthalates and phthalates alternatives in humans are necessary to evaluate potential human health effects from exposure to these chemicals.

Eligible Sample

Examined participants aged 6 years and older from a one-third sample.

Description of Laboratory Methodology

The test principle utilizes high performance liquid chromatography-electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS/MS) for the quantitative detection in urine of the following phthalate metabolites: monomethyl phthalate (MMP), monoethyl phthalate (MEP), monobutyl phthalate (MBP), mono-isobutyl phthalate (MIBP), mono (3-carboxypropyl) phthalate (MCPP), mono(2-ethylhexyl) phthalate (MEHP), monobenzyl phthalate (MBzP), monoisononyl phthalate (MNP), mono(2-ethyl-5-oxohexyl) phthalate (MEOHP), mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono(2-ethyl-5-carboxypentyl) phthalate (MECPP), monocarboxyoctyl phthalate (MCOP), monocarboxynonyl phthalate (MCNP)), and cyclohexane-1,2-dicarboxylic acid-mono(hydroxy-isononyl) ester (MHNCH)  (Silva, et al., 2007). Urine samples are processed using enzymatic deconjugation of the glucuronidated metabolites followed by on-line solid phase extraction (SPE) coupled with reversed phase HPLC-ESI-MS/MS. Assay precision is improved by incorporating isotopically-labeled internal standards of the phthalate metabolites and MHNCH. In addition, 4-methyl umbelliferone glucuronide is used to monitor deconjugation efficiency. This selective method allows for rapid detection of monoester metabolites of commonly used phthalate diesters and DINCH in human urine with limits of detection in the low ng/mL range.

Refer to NHANES 2011-2012 Lab Methods for Metabolites of Phthalates and Phthalate Alternatives for detailed description of the laboratory method used.

Laboratory Quality Assurance and Monitoring

Urine specimens are processed, stored, and shipped to the Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention for analysis.

Detailed specimen collection and processing instructions are discussed in the NHANES Laboratory Procedures Manual (LPM). Vials are stored under appropriate frozen (–20°C) conditions until they are shipped to National Center for Environmental Health for testing.

Mobile Examination Centers (MECs)

Laboratory team performance is monitored using several techniques. NCHS and contract consultants use a structured quality assurance evaluation during unscheduled visits to evaluate both the quality of the laboratory work and the quality-control procedures. Each laboratory staff person is observed for equipment operation, specimen collection and preparation; testing procedures and constructive feedback are given to each staff. Formal retraining sessions are conducted annually to ensure that required skill levels are maintained.

The NHANES QA/QC protocols meet the 1988 Clinical Laboratory Improvement Act mandates. Detailed QA/QC instructions are discussed in the NHANES LPM.

Analytical Laboratories

NHANES uses several methods to monitor the quality of the analyses performed by the laboratories. In the MEC, these methods include performing blind split samples collected on “dry run” sessions. In addition, contract laboratories randomly perform repeat testing on 2.0% of all specimens.

NCEH developed and distributed a quality control protocol for all the laboratories which outlined the Westgard rules (Westgard, et al., 1981) used when running NHANES specimens. Any problems encountered during shipping or receipt of specimens, instrument calibration, reagents, and any special considerations are submitted to NCHS. Summary statistics for each control pool, QC graphs, are reviewed by NCHS for trends or shifts in the data. The laboratories are required to explain any identified areas of concern.

All QC procedures recommended by the manufacturers were followed. Reported results for all assays meet the Division of Laboratory Sciences’ quality control and quality assurance performance criteria for accuracy and precision, similar to the Westgard rules (Westgard, et al., 1981).

Data Processing and Editing

The data were reviewed. Incomplete data or improbable values were sent to the performing laboratory for confirmation.

Analytic Notes

Refer to the 2011-2012 Laboratory Data Overview for general information on NHANES laboratory data.

Subsample Weights

Urinary phthalates and plasticizers metabolites were measured in a one third subsample of persons 6 years and older. Special sample weights are required to analyze these data properly. Specific sample weights for this subsample are included in this data file and should be used when analyzing these data.

Variance Estimation

The analysis of NHANES laboratory data must be conducted with the key survey design and basic demographic variables. The NHANES Demographic Data File contains demographic and sample design variables. The recommended procedure for variance estimation requires use of stratum and PSU variables (SDMVSTRA and SDMVPSU, respectively) in the demographic data file.

Links to NHANES Data Files

This laboratory data file can be linked to the other NHANES data files using the unique survey participant identifier SEQN.

Detection Limits

The detection limits were constant for all of the analytes in the data set.  Two variables are provided for each of these analytes.  The variable named URD___LC indicates whether the result was below the limit of detection.  There are two values: “0” and “1”.  “0” means that the result was at or above the limit of detection.   “1” indicates that the result was below the limit of detection. The other variable named URX___ provides the analytic result for that analyte. For analytes with analytic results below the lower limit of detection (i.e., URD___LC=1), an imputed fill value was placed in the analyte results field. This value is the lower limit of detection divided by square root of 2 (LLOD/sqrt(2)).

The lower limit of detections (LLOD, in ng/mL) for the phthalate metabolites and MHNCH are:

 

Analyte Item ID LLOD
Mono(carboxyoctyl) phthalate URXCOP 0.2
Mono(carboxynonyl) phthalate URXCNP 0.2
Mono-2-ethyl-5-carboxypentyl phthalate URXECP 0.2
Mono-n-butyl phthalate URXMBP 0.4
Mono-(3-carboxypropyl) phthalate URXMC1 0.2
Mono-ethyl phthalate URXMEP 0.6
Mono-(2-ethyl-5-hydroxyhexyl) URXMHH 0.2
Mono-(2-ethyl)-hexyl phthalate URXMHP 0.5
Mono-isobutyl pthalate URXMIB 0.2
Mono-n-methyl phthalate URXMNM 0.5
Mono-isononyl phthalate URXMNP 0.5
Mono-(2-ethyl-5-oxohexyl) URXMOH 0.2
Mono-benzyl phthalate URXMZP 0.3
Cyclohexane-1,2-dicarboxylic acid monohydroxy isononyl ester URXMHN 0.4

Please refer to the NHANES Analytic Guidelines and the on-line NHANES Tutorial for further details on the use of sample weights and other analytic issues.

References

Codebook and Frequencies

SEQN - Respondent sequence number

Variable Name:
SEQN
SAS Label:
Respondent sequence number
English Text:
Respondent sequence number.
Target:
Both males and females 6 YEARS - 150 YEARS

WTSA2YR - Subsample A weights

Variable Name:
WTSA2YR
SAS Label:
Subsample A weights
English Text:
Subsample A weights
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
12199.652219 to 643202.3505 Range of Values 2551 2551
. Missing 43 2594

URXCNP - Mono(carboxynonyl) Phthalate (ng/mL)

Variable Name:
URXCNP
SAS Label:
Mono(carboxynonyl) Phthalate (ng/mL)
English Text:
Mono(carboxynonyl) Phthalate (ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.14 to 603.3 Range of Values 2489 2489
. Missing 105 2594

URDCNPLC - Mono(carboxynonyl) Phthalate comment

Variable Name:
URDCNPLC
SAS Label:
Mono(carboxynonyl) Phthalate comment
English Text:
Mono(carboxynonyl) Phthalate comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2470 2470
1 Below lower detection limit 19 2489
. Missing 105 2594

URXCOP - Mono(carboxyoctyl) Phthalate (ng/mL)

Variable Name:
URXCOP
SAS Label:
Mono(carboxyoctyl) Phthalate (ng/mL)
English Text:
Mono(carboxyoctyl) Phthalate (ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.3 to 1773.5 Range of Values 2489 2489
. Missing 105 2594

URDCOPLC - Mono(carboxyoctyl) Phthalate comment

Variable Name:
URDCOPLC
SAS Label:
Mono(carboxyoctyl) Phthalate comment
English Text:
Mono(carboxyoctyl) Phthalate comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2489 2489
1 Below lower detection limit 0 2489
. Missing 105 2594

URXECP - Mono-2-ethyl-5-carboxypentyl phthalate

Variable Name:
URXECP
SAS Label:
Mono-2-ethyl-5-carboxypentyl phthalate
English Text:
Mono-2-ethyl-5-carboxypentyl phthalate
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.14 to 1548.4 Range of Values 2489 2489
. Missing 105 2594

URDECPLC - Mono-2ethyl5carboxypentyl phthalate cmt

Variable Name:
URDECPLC
SAS Label:
Mono-2ethyl5carboxypentyl phthalate cmt
English Text:
Mono-2-ethyl-5-carboxypentyl phthalate comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2482 2482
1 Below lower detection limit 7 2489
. Missing 105 2594

URXMBP - Mono-n-butyl phthalate (ng/mL)

Variable Name:
URXMBP
SAS Label:
Mono-n-butyl phthalate (ng/mL)
English Text:
Mono-n-butyl phthalate (ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.28 to 2462.3 Range of Values 2489 2489
. Missing 105 2594

URDMBPLC - Mono-n-butyl phthalate comment code

Variable Name:
URDMBPLC
SAS Label:
Mono-n-butyl phthalate comment code
English Text:
Mono-n-butyl phthalate comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2350 2350
1 Below lower detection limit 139 2489
. Missing 105 2594

URXMC1 - Mono-(3-carboxypropyl) phthalate (ng/mL)

Variable Name:
URXMC1
SAS Label:
Mono-(3-carboxypropyl) phthalate (ng/mL)
English Text:
Mono-(3-carboxypropyl) phthalate (ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.14 to 2597.3 Range of Values 2489 2489
. Missing 105 2594

URDMC1LC - Mono-(3-carboxypropyl) phthalate cmt

Variable Name:
URDMC1LC
SAS Label:
Mono-(3-carboxypropyl) phthalate cmt
English Text:
Mono-(3-carboxypropyl) phthalate comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2449 2449
1 Below lower detection limit 40 2489
. Missing 105 2594

URXMEP - Mono-ethyl phthalate (ng/mL)

Variable Name:
URXMEP
SAS Label:
Mono-ethyl phthalate (ng/mL)
English Text:
Mono-ethyl phthalate (ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.42 to 30321 Range of Values 2489 2489
. Missing 105 2594

URDMEPLC - Mono-ethyl phthalate comment code

Variable Name:
URDMEPLC
SAS Label:
Mono-ethyl phthalate comment code
English Text:
Mono-ethyl phthalate comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2486 2486
1 Below lower detection limit 3 2489
. Missing 105 2594

URXMHH - Mono-(2-ethl-5-hydrxhxyl) phthte (ng/mL)

Variable Name:
URXMHH
SAS Label:
Mono-(2-ethl-5-hydrxhxyl) phthte (ng/mL)
English Text:
Mono-(2-ethl-5-hydrxhxyl) phthte (ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.14 to 1186.6 Range of Values 2489 2489
. Missing 105 2594

URDMHHLC - Mono(2ethyl5hydroxyhexyl) phthalate cmt

Variable Name:
URDMHHLC
SAS Label:
Mono(2ethyl5hydroxyhexyl) phthalate cmt
English Text:
Mono(2ethyl5hydroxyhexyl) phthalate cmt
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2483 2483
1 Below lower detection limit 6 2489
. Missing 105 2594

URXMHP - Mono-(2-ethyl)-hexyl phthalate (ng/mL)

Variable Name:
URXMHP
SAS Label:
Mono-(2-ethyl)-hexyl phthalate (ng/mL)
English Text:
Mono-(2-ethyl)-hexyl phthalate (ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.35 to 160.3 Range of Values 2489 2489
. Missing 105 2594

URDMHPLC - Mono-(2-ethyl)-hexyl phthalate comment

Variable Name:
URDMHPLC
SAS Label:
Mono-(2-ethyl)-hexyl phthalate comment
English Text:
Mono-(2-ethyl)-hexyl phthalate comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 1910 1910
1 Below lower detection limit 579 2489
. Missing 105 2594

URXMNM - Mono-n-methyl phthalate

Variable Name:
URXMNM
SAS Label:
Mono-n-methyl phthalate
English Text:
Mono-n-methyl phthalate
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.35 to 1254.2 Range of Values 2489 2489
. Missing 105 2594

URDMNMLC - Mono-n-methyl phthalate comment code

Variable Name:
URDMNMLC
SAS Label:
Mono-n-methyl phthalate comment code
English Text:
Mono-n-methyl phthalate comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 1603 1603
1 Below lower detection limit 886 2489
. Missing 105 2594

URXMNP - Mono-isononyl phthalate (ng/mL)

Variable Name:
URXMNP
SAS Label:
Mono-isononyl phthalate (ng/mL)
English Text:
Mono-isononyl phthalate (ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.35 to 305.8 Range of Values 2489 2489
. Missing 105 2594

URDMNPLC - Mono-isononyl phthalate comment code

Variable Name:
URDMNPLC
SAS Label:
Mono-isononyl phthalate comment code
English Text:
Mono-isononyl phthalate comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 1461 1461
1 Below lower detection limit 1028 2489
. Missing 105 2594

URXMOH - Mono-(2-ethyl-5-oxohexyl) phthalate

Variable Name:
URXMOH
SAS Label:
Mono-(2-ethyl-5-oxohexyl) phthalate
English Text:
Mono-(2-ethyl-5-oxohexyl) phthalate
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.14 to 528.7 Range of Values 2489 2489
. Missing 105 2594

URDMOHLC - Mono-(2-ethyl-5-oxohexyl) phthalate cmt

Variable Name:
URDMOHLC
SAS Label:
Mono-(2-ethyl-5-oxohexyl) phthalate cmt
English Text:
Mono-(2-ethyl-5-oxohexyl) phthalate cmt
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2480 2480
1 Below lower detection limit 9 2489
. Missing 105 2594

URXMZP - Mono-benzyl phthalate (ng/mL)

Variable Name:
URXMZP
SAS Label:
Mono-benzyl phthalate (ng/mL)
English Text:
Mono-benzyl phthalate (ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.21 to 282.4 Range of Values 2489 2489
. Missing 105 2594

URDMZPLC - Mono-benzyl phthalate comment code

Variable Name:
URDMZPLC
SAS Label:
Mono-benzyl phthalate comment code
English Text:
Mono-benzyl phthalate comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2443 2443
1 Below lower detection limit 46 2489
. Missing 105 2594

URXMIB - Mono-isobutyl phthalate

Variable Name:
URXMIB
SAS Label:
Mono-isobutyl phthalate
English Text:
Mono-isobutyl phthalate
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.14 to 627 Range of Values 2489 2489
. Missing 105 2594

URDMIBLC - Mono-isobutyl phthalate comment code

Variable Name:
URDMIBLC
SAS Label:
Mono-isobutyl phthalate comment code
English Text:
Mono-isobutyl phthalate comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2464 2464
1 Below lower detection limit 25 2489
. Missing 105 2594

URXMHNC - MHNC (ng/mL)

Variable Name:
URXMHNC
SAS Label:
MHNC (ng/mL)
English Text:
MHNC (ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.28 to 168.1 Range of Values 2489 2489
. Missing 105 2594

URDMCHLC - MHNC comment code

Variable Name:
URDMCHLC
SAS Label:
MHNC comment code
English Text:
MHNC comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 605 605
1 Below lower detection limit 1884 2489
. Missing 105 2594

URXUCR - Creatinine, urine (mg/dL)

Variable Name:
URXUCR
SAS Label:
Creatinine, urine (mg/dL)
English Text:
Creatinine, urine (mg/dL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
4 to 800 Range of Values 2525 2525
. Missing 69 2594