The China Benzene Sperm Study (C-BASS)

The China Benzene and Sperm Study (C-BASS) investigates the association between exposure to benzene in the workplace and genetic damage to sperm in Tianjin, China.

Shoe factory worker. Tianjin, China.

What the C-BASS Study investigates:

  • Whether exposure to benzene impacts:
    • the number of chromosomes in sperm/incidence of aneuploidy (abnormal numbers of chromosomes)
    • structural changes in sperm
    • DNA fragmentation
    • DNA breakages
  • Whether aneuploidy in sperm cells is related to aneuploidy in blood cells in the same individual.

C-BASS Findings: (Go to Findings)

Exposures Studied:

  • Benzene
    • In particular, looking at occupational exposures below the U.S. OSHA permissible exposure limit.

Health Outcomes Studied:

  • Number of chromosomes in sperm (aneuploidy)
  • Structural changes in sperm
  • DNA fragmentation
  • DNA breakages

About Benzene:

  • Benzene is a ubiquitous environmental pollutant present in crude oil, smoke, gasoline, paints, adhesives and solvents.
  • Benzene is listed among the International Agency for Research on Cancer (IARC) Group 1 human carcinogens. It is found to:
    • Induce leukemia & lymphoma
    • Be associated with increased chromosomal anomalies in somatic cells
  • Government imposed exposure limits for benzene:
    • The United States Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) = 1 ppm (over an 8-hr time-weighted average (TWA))
    • China Occupational Exposure Limit (OEL) = 1.9 ppm (over an 8-hr time-weighted average (TWA))

Why Study Benzene and Sperm?

  • Paternal exposures can impact pregnancies and offspring in many ways, including heritable changes in the sperm genome. Specifically, there is a strong paternal contribution for de novo gene mutations, sex chromosomal aneuploidies (abnormal numbers of chromosomes) and structural aberrations in offspring.
  • The purposes of this study are to examine the effects of benzene, a well-recognized mutagen, on DNA and chromosomal damage in human sperm and to determine the association between chromosomal damage in sperm and blood cells within the same individuals.
  • In the U.S., benzene is a highly regulated chemical due its ability to induce leukemia and other  blood disorders at exposure levels even below 1 ppm, the Permissible Exposure Limit (8 hour) set by OSHA.
  • There is considerable epidemiological evidence that exposure of the father to environmental or occupational agents can  lead to abnormal reproductive outcomes.
  • Benzene induces chromosomal damage in white blood cells, but it is not clear whether it induces aneuploidy in sperm or if the resulting offspring would be affected by such damage.

Benzene glue in a shoe factory. Tianjin, China.


  • Tianjin, China

Study Participants:

  • In 2004, 34 occupationally-exposed men and 34 un-exposed men were enrolled in Tianjin, China.
  • 34 occupationally-exposed men were recruited from factories where benzene-containing solvents were used (factories making shoes, paper bags, and sandpaper)
  • 34 unexposed men were recruited from an ice cream factory and meat-packing plant
  • Eligibility criteria:
    • 18 to 50 years old
    • worked at the factory for at least one year
    • no history of cancer or vasectomy

Data Collection:

  • Exposure Assessment Phase:
    • 96 men participated in a brief interview, wore a personal passive-air badge monitor for an 8-hour work day and provided a urine spot sample at the end of their shift.
    • Approximately one month later, they repeated this process to provide a second air and urine sample.
  • Semen Phase:
    • Men visited the Tianjin 3rdMunicipal Hospital where they were interviewed and examined by a urologist, and provided samples:
      • After abstaining from ejaculation for 2 days, a semen sample was collected via masturbation.
      • A fasting blood sample.

Research Team:

  • Brenda Eskenazi, PhD
  • Andrew Wyrobek, PhD, Life Sciences Division, Lawrence Berkeley National Laboratory
  • Rosana Hernandez Weldon, PhD
  • Caihong Xing, Life Sciences Division, Lawrence Berkeley National Laboratory and National Institute of Occupational Health and Poison Control, Chinese Center for Disease Control and Prevention
  • Guilan Li, National Institute of Occupational Health and Poison Control, Chinese Center for Disease Control and Prevention
  • Francesco Marchetti, Life Sciences Division, Lawrence Berkeley National Laboratory
  • Thomas Schmid, Life Sciences Division, Lawrence Berkeley National Laboratory
  • Suramya Waidyanatha, University of North Carolina, Chapel Hill
Funded By: Duration: Study Contact:
  • The National Institute for Environmental  Health Sciences (NIEHS)
  • U.S. Environmental Protection Agency (EPA)
    Superfund Research Program
2004, ongoing
Brenda Eskenazi, PhD
Director of CERCH
510-642-3496Rosana Hernandez Weldon, PhD
AGES Study Coordinator
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