Systematic review of the association between oil and natural gas extraction processes and human reproduction

Abstract

This systematic review identified 45 original published research articles related to oil and gas extraction activities and human reproductive endpoints. Reproductive outcomes were categorized as [1] birth outcomes associated with maternal exposure, [2] semen quality, fertility, and birth outcomes associated with adult paternal exposure, [3] reproductive cancers, and [4] disruption of human sex steroid hormone receptors. The results indicate there is moderate evidence for an increased risk of preterm birth, miscarriage, birth defects, decreased semen quality, and prostate cancer. The quality of the evidence is low and/or inadequate for stillbirth, sex ratio, and birth outcomes associated with paternal exposure, and testicular cancer, female reproductive tract cancers, and breast cancer, and the evidence is inconsistent for an increased risk of low birth weight; therefore, no conclusions can be drawn for these health effects. There is ample evidence for disruption of the estrogen, androgen, and progesterone receptors by oil and gas chemicals, which provides a mechanistic rationale for how exposure to oil and gas activities may increase the health risks we have outlined. The results from this systematic review suggest there is a negative impact on human reproduction from exposure to oil and gas activities. Many of the 45 studies reviewed identified potential human health effects. Most of these studies focused on conventional oil and gas activities. Few studies have been conducted to evaluate the impact of unconventional oil and gas operations on human health. The impact of unconventional oil and gas activities may be greater than that of conventional activity, given that unconventional activities employ many of the same approaches and use dozens of known endocrine-disrupting chemicals in hydraulic fracturing.

Keywords: Birth defects; cancer; endocrine disrupting chemicals; environmental pollution; fracking; hormonal activity; human reproduction; hydraulic fracturing; oil and natural gas; prenatal exposure; preterm birth; semen quality.

FIGURE 1

Inclusion flow chart. Summary of literature search strategies, levels of screening, and final inclusion.

FIGURE 2

Integration of evidence of health effect. Visualization of integration of the evidence of a health effect based on each articles finding and the level of evidence and confidence ratings for endpoints (A) Preterm Birth, (B) Miscarriage, (C) Stillbirth, (D) Low Birth Weight, (E) Birth Defects, (F) Sex Ratio, (G) Semen Quality and Fertility, (H) Paternal Birth Outcomes, (I) Prostate Cancer, (J) Testicular Cancer, (K) Female Reproductive Tract Cancers, and (L) Breast Cancer. The total number of articles for each endpoint is indicated below each chart. Evidence was integrated for each endpoint based on each article’s level of evidence and level of confidence. High, moderate, and low level of confidence findings were weighted by multiplying the number of articles by 3 for high, 2 for moderate, and 1 for low for all studies except where noted. *Four studies were not independent of each other and integration of evidence was adjusted (Materials and Methods). ↑ Indicates increased risk. ↓ Indicates decreased risk. **Two studies analyzed the same cohort, only the most recent study was included (Materials and Methods).

FIGURE 3

In vitro effect/no effect summary. Summary of the number of in vitro studies reporting effect or no effect on individual steroid hormone receptors including (A) estrogen, (B) androgen, and (C) progesterone. The total number of articles for each endpoint is indicated below each chart.