Fracking Chemicals Linked to Reduced Sperm Count in Mice

Fracking rig
Fracking rig
Prenatal exposure to oil and gas chemicals used in hydraulic fracturing could cause reproductive health problems.

Male mice that were prenatally exposed to levels of chemicals used in the oil and natural drilling technique known as hydraulic fracturing, or fracking, found in the environment had reduced sperm counts in adulthood, according to research published in Endocrinology.

Endocrine-disrupting chemicals (EDCs), or chemicals that affect hormone action, can affect critical periods of human development that lead to disease, if they are present in certain environmental conditions.

More than 1000 chemicals are used throughout the hydraulic fracturing process, and approximately 100 of these are possible EDCs. Hydraulic fracturing injects water mixed with chemicals into suspended solids to release trapped gas or oil, and these operations can lead to chemical complications like miscarriage, preterm birth, and infertility.

Susan Nagel, PhD of the University of Missouri in Columbia, Missouri, and colleagues measured the actions of 24 chemicals that are used or are produced by oil and gas operations. They used a reporter gene assay in human endometrical cancer cells to determine that 23 were EDCs. They found that the 23 EDCs can activate or inhibit estrogen, androgen, glucocorticoid, progesterone, and thyroid receptors.

The researchers then tested the reproductive and developmental outcomes of prenatal exposure to these chemicals with a laboratory mixture that they tested on male mice.

“We report, for the first time, adverse male reproductive health outcomes in mice (decreased epididymal sperm counts, increased testis weights, increased serum testosterone) after prenatal exposure to a laboratory-created mixture of oil and gas operation chemicals provided via drinking water at concentrations equal to and below those detected in industry WW samples,” the researchers wrote.

The researchers tested water from drill sites in Garfield County, Colorado. They prepared a mixture of 23 chemicals and added it to the drinking water of pregnant mice. The mice were exposed to drinking water with 3 mcg/kg, 30 mcg/kg, 300 mcg/kg, or 3000 mcg/kg of chemical doses. The mice drank the water from the 11th day of pregnancy until they gave birth. 

The researchers measured the serum testosterone and sperm count of the male offspring and compared them with offspring of mothers who were not exposed to the chemical mixture.

Prenatal exposure to the 23 chemicals caused decreased sperm counts and increased testes, body, heart, and thymus weights. It also increased serum testosterone in male mice, which suggests that multiple organ systems are affected by the chemicals. 

The offspring of mice with 3 mcg/kg and 300 mcg/kg doses also had increased heart weights and had a reported increased cardiac myocyte size, which suggests that the structure of the heart is still affected in adulthood and can further lead to cardiac hypertrophy.

“It is clear EDCs used in fracking can act alone or in combination with other chemicals to interfere with the body’s hormone function,” Dr Nagel said in a press release. “These mixture interactions are complex and challenging to predict. More research is needed to assess the many other chemicals used for fracking and to determine how they may be contributing to health outcomes.”


  1. Kassotis CD, Klemp KC, Vu DC, et al. Endocrine-Disrupting Activity of Hydraulic Fracturing Chemicals and Adverse Health Outcomes After Prenatal Exposure in Male Mice. Endocrinology. 2015;doi:10.1210/en.2015-1375.