Key Concepts About Identifying Environmental Chemical Variable Names and File Locations

NHANES environmental chemical variables include laboratory measurements from blood and urine specimens. They are located in separate data files within the Laboratory section of the NHANES website for each two-year survey cycle. Data files are organized by type of specimens and chemical groups. The table below provides an example of how the data files are organized for the years 1999-2004.  As evident, the availability of the chemicals differs by survey cycle.

 

Environmental Chemical Groups and File Names

Chemical Group s

Specimen

1999-2000 File Names

2001-2002 File Names

2003-2004 File Names

Tobacco smoke (Cotinine)

Serum

LAB06

L06_B

L06COT_C

Metals

 

 

 

 

  Lead, Cadmium, Mercury

Blood

LAB06

L06_B

L06BMT_C

  Heavy Metals

Urine

LAB06HM

L06HM_B

L06HM_C

  Mercury

Urine

LAB06

L06_B

L06UHG_C

  Total Arsenic and Speciated Arsenics

Urine

na

na

L06UAS_C

Persistent organic pollutants

 

 

 

 

  Dioxins, Furans, and Coplanar Polychlorinated Biphenyls (PCBs)

Serum

LAB28POC

L28POC_B

L28DFP_C

  Non-dioxin-like Polychlorinated Biphenyls (PCBs)

Serum

LAB28POC

L28POC_B

L28NPB_C

  Organochlorine Pesticides

Serum

LAB28POC

L28POC_B

L28OCP_C

Polybrominated Diphenyl Ethers and Polybrominated Biphenyl

Serum

na

na

L28PBE_C

Polyfluoroalkyl compounds (pooled)

Surplus Serum

SSPFC_A *

PFC_POOL *

L24PFC_C

Polycyclic Aromatic Hydrocarbons

Urine

PHPYPA

PHPYPA_B

L31PAH_C

Phthalates

Urine

PHPYPA

PHPYPA_B

L24PH_C

Phytoestrogens

Urine

PHPYPA

PHPYPA_B

L06PHY_C

Pesticides

Urine

LAB26PP

L26PP_B

L26UPP_C

Environmental Phenols

Urine

na

na

L24EPH_C

Acrylamide and Glycidamide

Blood

na

na

L06AGE_C

Perchlorate

Urine

na

na

L04PER_C

Volatile Organic Compounds

Blood 

LAB04

L04VOC_B

L04VOC_C

* Pooled serum results, not individual sample.

Phthalate Data (1999-2004): Instructive procedures and program

For the purpose of this tutorial, you can go through the procedures to download data , prepare an analytic dataset, and analyze urinary phthalates data from NHANES 1999-2004.

On each two-year survey cycle page on the NHANES website, click the Laboratory link, and then the Variable List link. Use the search feature to locate variables related to "phthalate." Note the number of environmental chemicals available and the name of the file that contains the variables. Variable names and SAS labels may change across survey cycles, so it is important to check for changes between survey cycles.

The corresponding data files for 1999-2000, 2001-2002, and 2003-2004 are PHPYPA, PHPYPA_B, and L24PH_C. Consult the documentation to determine which specific urinary phthalate metabolites were measured in each survey cycle and if there are any auxiliary variables, for example, the variable indicating the Limit of Detection for each metabolite or the urine creatinine variable. In this example, the number of urinary phthlate metabolites measured changed over three survey cycle periods:  7 were measured in 1999-2000 survey, 12 were measured in 2001-2002, and 13 were measured in 2003-2004 survey cycle. In addition, a variable indicating a comment about the Limit of Detection was included in 2003-2004 data, but not in the 1999-2000 and 2001-2002 data files for this group of environmental chemicals.

 

Phthalate Files and Variables

Survey years 1999-2000 2001-2002 2003-2004
File name PHPYPA PHPYPA_B L24PH_C
Variable name for Mono-(2-ethyl)-hexyl phthalate URXMHP URXMHP URXMHP
Variable name for Mono-(2-ethyl)-hexyl phthalate comment na na URDMHPLC

 

 

 

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