Key issues of endocrine disrupting chemicals

The State of the Science of Endocrine Disrupting Chemicals prepared by a group of experts jointly by UNEP and the WHO presents objective scientific findings, conclusions and key concerns on the Endocrine Disrupting Chemicals (EDCs) in order to address the concerns about potential adverse health effects of chemicals on humans and wildlife.

Key concerns extracted from the Summary for Decision-Makers include:

  • Human and wildlife health depends on the ability to reproduce and develop normally. This is not possible without a healthy endocrine system.
  • Three strands of evidence fuel concerns over endocrine disruptors:
    • The high incidence and the increasing trends of many endocrine-related disorders in humans;
    • Observations of endocrine-related effects in wildlife populations;
    • The identification of chemicals with endocrine disrupting properties linked to disease outcomes in laboratory studies.
  • Many endocrine-related diseases and disorders are on the rise.
    • Large proportions (up to 40%) of young men in some countries have low semen quality, which reduces their ability to father children.
    • The incidence of genital malformations, such as non-descending testes (cryptorchidisms) and penile malformations (hypospadias), in baby boys has increased over time or levelled off at unfavourably high rates.
    • The incidence of adverse pregnancy outcomes, such as preterm birth and low birth weight, has increased in many countries.
    • Neurobehavioural disorders associated with thyroid disruption affect a high proportion of children in some countries and have increased over past decades.
    • Global rates of endocrine-related cancers (breast, endometrial, ovarian, prostate, testicular and thyroid) have been increasing over the past 40–50 years.
    • There is a trend towards earlier onset of breast development in young girls in all countries where this has been studied. This is a risk factor for breast cancer.
    • The prevalence of obesity and type 2 diabetes has dramatically increased worldwide over the last 40 years. WHO estimates that 1.5 billion adults worldwide are overweight or obese and that the number with type 2 diabetes increased from 153 million to 347 million between 1980 and 2008.
  • Close to 800 chemicals are known or suspected to be capable of interfering with hormone receptors, hormone synthesis or hormone conversion. However, only a small fraction of these chemicals have been investigated in tests capable of identifying overt endocrine effects in intact organisms.
  • Human and wildlife populations all over the world are exposed to EDCs.
  • Significant knowledge gaps exist as to associations between exposures to EDCs and other endocrine diseases.
  • Worldwide, there has been a failure to adequately address the underlying environmental causes of trends in endocrine diseases and disorders.
  • Internationally agreed and validated test methods for the identification of endocrine disruptors capture only a limited range of the known spectrum of endocrine disrupting effects. This increases the likelihood that harmful effects in humans and wildlife are being overlooked.
  • Disease risk due to EDCs may be significantly underestimated.
    • A focus on linking one EDC to one disease severely underestimates the disease risk from mixtures of EDCs. We know that humans and wildlife are simultaneously exposed to many EDCs; thus, the measurement of the linkage between exposure to mixtures of EDCs and disease or dysfunction is more physiologically relevant. In addition, it is likely that exposure to a single EDC may cause disease syndromes or multiple diseases, an area that has not been adequately studied.
  • An important focus should be on reducing exposures by a variety of mechanisms. Government actions to reduce exposures, while limited, have proven to be effective in specific cases. This has contributed to decreases in the frequency of disorders in humans and wildlife.
  • Despite substantial advances in our understanding of EDCs, uncertainties and knowledge gaps still exist that are too important to ignore. These knowledge gaps hamper progress towards better protection of the public and wildlife. An integrated, coordinated international effort is needed to define the role of EDCs in current declines in human and wildlife health and in wildlife populations.