Table of Contents

Component Description

Since 1999, CDC has measured phthalate metabolites in human urine to assess exposure to phthalates (CDC 2017). Di-2-ethylhexyl phthalate (DEHP) is a commonly used plasticizer. The use of DEHP in the U.S. market appears to be decreasing, at least in part because of legislative efforts, while the use of di-isononyl phthalate (DiNP), one of the replacements of DEHP, and other phthalate alternatives, may be rising (Calafat et al. 2011;Zota et al. 2014).  Di-2-ethylhexyl terephthalate (DEHTP), a structural isomer of DEHP and one of such alternatives, has been used as a plasticizer for polymers contained in consumer products (Beeler 1976).  To better understand exposure to phthalates alternatives, we quantified mono-2-ethyl-5-hydroxyhexyl terephthalate (MEHHTP), mono-2-ethyl-5-carboxypentyl terephthalate (MECPTP), two metabolites of DEHTP, and monooxoisononyl phthalate (MONP), an additional metabolite of DiNP, in one third subsample of participants 3+ years of age from NHANES 2015-2016. 

Eligible Sample

All participants aged 3-5 years old and an one-third sample of participants aged 6 and older from NHANES 2015-2016 with stored urine.

Description of Laboratory Methodology

We measured urinary MEHHTP, MECPTP and MONP by an on-line solid phase extraction coupled with isotope dilution-high performance liquid chromatography tandem mass spectrometry approach previously described (Silva et al. 2013).

Refer to the Laboratory Method Files section for detailed laboratory procedure manual(s) of the methods used.

There were no changes to the lab equipment or lab site for this component compared with those used for measuring other phthalates and DINCH metabolites in the same one-third subsample of participants 3 years of age and older in NHANES 2015-2016. If the concentration of a metabolite was less than the limit of detection (LOD), then the imputed value was used. The imputed value was calculated as the LOD divided by the square root of 2 (Hornung and Reed 1990); imputed values are provided in the NHANES public release file.

Laboratory Quality Assurance and Monitoring

The analytical measurements were conducted following strict quality control/quality assurance CLIA guidelines. Along with the study samples, each analytical run included high- and low-concentration quality control materials (QCs) and reagent blanks to assure the accuracy and reliability of the data. The concentrations of the high-concentration QCs and the low-concentration QCs, averaged to obtain one measurement of high-concentration QC and low-concentration QC for each run, were evaluated using standard statistical probability rules (Caudill et al. 2008).

Data Processing and Editing

Data were received after all analyses were complete. The data were not edited.

Data Access: All data are publicly available.

Analytic Notes

Refer to the 2015-2016 Laboratory Data Overview for general information on NHANES laboratory data.

Subsample weights

MEHHTP, MECPTP, and MONP were measured in all persons 3-5 years of age and in a one-third subsample for persons 6 years of age and older. Special sample weights, included in this data file, are required to analyze these data properly.

Demographic and Other Related Variables

The analysis of NHANES laboratory data must be conducted with the key survey design and basic demographic variables. The NHANES 2015-2016 Demographic Data File contains demographic data, health indicators, and other related information collected during household interviews as well as the 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.

This laboratory data file can be linked to other NHANES data files using the unique survey participant identifier (i.e., SEQN).

Detection Limits

Detection limits were constant for all of the analytes in the data set. Two variables are provided for each analyte.

The variable name ending in “L” (ex., SSMHHTL) indicates whether the result was below the limit of detection: the value “0” means that the result was at or above the limit of detection, “1” indicates that the result was below the limit of detection. For analytes with analytic results below the lower limit of detection (ex., SSMHHTL=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). The other variable prefixed SS (ex., SSMHHT) provides the analytic result for that analyte.

The lower limit of detection (LLOD, in ng/mL) for MEHHTP, MECPTP, and MONP are:

Variable Name

SAS Label 

LLOD 

SSMHHT

Mono-2-ethyl-5-hydroxyhexyl terephthalate (µg/L)

0.4

SSECPT

Mono-2-ethyl-5-carboxypentyl terephthalate (µg/L)

0.2

SSMONP

Monooxoisononyl phthalate  (µg/L)

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 3 YEARS - 150 YEARS

WTSB2YR - Subsample B weights

Variable Name:
WTSB2YR
SAS Label:
Subsample B weights
English Text:
Subsample B weights
Target:
Both males and females 3 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 to 874638.01159 Range of Values 2971 2971
. Missing 0 2971

SSMHHT - Mono2ethyl5hydroxyhexyl terephth (ug/L)

Variable Name:
SSMHHT
SAS Label:
Mono2ethyl5hydroxyhexyl terephth (ug/L)
English Text:
Mono2ethyl5hydroxyhexyl terephth (ug/L)
Target:
Both males and females 3 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.3 to 876.6 Range of Values 2971 2971
. Missing 0 2971

SSMHHTL - Mono2ethy-5hydroxyhexyl terephth cmt cd

Variable Name:
SSMHHTL
SAS Label:
Mono2ethy-5hydroxyhexyl terephth cmt cd
English Text:
Mono2ethy-5hydroxyhexyl terephth cmt cd
Target:
Both males and females 3 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2857 2857
1 Below lower detection limit 114 2971
. Missing 0 2971

SSECPT - Mono2ethyl5carboxypentyl terephth (ug/L)

Variable Name:
SSECPT
SAS Label:
Mono2ethyl5carboxypentyl terephth (ug/L)
English Text:
Mono2ethyl5carboxypentyl terephth (ug/L)
Target:
Both males and females 3 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.1 to 4312 Range of Values 2971 2971
. Missing 0 2971

SSECPTL - Mono2ethyl5carboxypentyl terephth cmt cd

Variable Name:
SSECPTL
SAS Label:
Mono2ethyl5carboxypentyl terephth cmt cd
English Text:
Mono2ethyl5carboxypentyl terephth cmt cd
Target:
Both males and females 3 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2969 2969
1 Below lower detection limit 2 2971
. Missing 0 2971

SSMONP - Monooxoisononyl phthalate (ug/L)

Variable Name:
SSMONP
SAS Label:
Monooxoisononyl phthalate (ug/L)
English Text:
Monooxoisononyl phthalate (ug/L)
Target:
Both males and females 3 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.3 to 727.1 Range of Values 2971 2971
. Missing 0 2971

SSMONPL - Monooxoisononyl phthalate cmt cd

Variable Name:
SSMONPL
SAS Label:
Monooxoisononyl phthalate cmt cd
English Text:
Monooxoisononyl phthalate cmt cd
Target:
Both males and females 3 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2779 2779
1 Below lower detection limit 192 2971
. Missing 0 2971