While interviewing a cancer researcher a few years ago, she made a comment to me almost in passing that was so powerful it has stuck with me. She said, “all cancers are the result of a combination of environmental and genetic factors.”
Throughout our lives we are exposed to an enormous range of man-made chemicals, from food, water, medicines, cosmetics, clothes, shoes and the air we breathe. So when I learned about a new European study, State of the Art Report on Mixture Toxicity, it caught my attention. At the request of the European Union, researchers at the University of Gothenburg, Sweden, looked at the "chemical cocktail" exposure risk that may have adverse effect on human health.
What they found is scary and prolific. To map out the current situation, Swedish reseachers collaborated with University of London researchers to carry out a review using state-of-the-art toxicology and ecotoxicology techniques. The study showed the combined cocktail effect of environmental chemicals is greater and far more toxic than the effect of the chemicals individually, even if each substance alone is below its own risk limit.
The research focused particularly on endocrine disrupters. These are substances that act like hormones and disturb the normal functioning of the endocrine system. The endocrine system is a network of glands and hormones that regulate many of the body's functions, including growth, development and maturation.
Endocrine disrupter chemicals like PVC, flame-retardants, phthalates, dioxins, PCBs and bisphenol-A are suspected of interfering with the production and performance of hormones. Such effects have already been seen in animals by impairing reproduction, development or immunity.
A number of studies show that multiple endocrine disrupters can be linked to harmful effects on human health too. Exposure may be through everyday items—food, plastics, paints and cosmetics, among others. These chemicals are thought to be responsible for declining sperm counts and quality, genital malformations, retarded sexual development and increased incidences of certain types of cancer.
So how prolific are these chemicals? Well, in 2005 a U.S. study showed that newborn babies have, on average, 200 non-natural chemicals in their blood - including pesticides, dioxins, industrial chemicals and flame-retardants. A Swedish University of Agricultural Sciences study found 57 different pesticides in that country’s rivers and streams, many of them occurring simultaneously.
However, there's a catch. The effects of chemicals on humans and the environment are traditionally evaluated on the basis of single substances, chemical by chemical. Experts now regard the typical chemical-by-chemical approach as insufficient in risk assessment. The EU Research has shown that this approach is inadequate because the chemicals that we are exposed to form a “complex cocktail” and, to date, mixing compounds has rarely been studied.
While the EU researchers conclude more information is needed on a range of topics to fully understand the potential effects of endocrine disruption, a number of scientific observations have been made in which endocrine disruptors may play a role. Here are just a few:
- Congenital malformations in children: In recent years there has been an increase in the incidence of hypospadias, a congenital abnormality of the urethra in the penis, and cryptorchidism, the undescended testes in males.
Researchers at Mount Sinai School of Medicine found young girls exposed to three common chemical classes—phenols, phthalates and phytoestrogens, found in nail polishes, shampoos and scented lotions— may disrupt the timing of pubertal development, and put girls at risk for cancer and diabetes later in life. It’s the first study to examine the effects of these chemicals on pubertal development and is published online in the journal Environmental Health Perspectives.
- Cancer: Increased incidences of hormone-related cancers in adult women (breast and ovary) and men (testes and prostate) have been observed in the West and in countries adopting Western lifestyles. While chemicals are suspect, a causal association with chemicals has not been shown, and numerous other lifestyle factors are known to be important.
- The U.S. Environmental Protection Agency (EPA) announced March 22, 2010, it plans to tighten control on four cancer-causing waterborne containments used in textile processing and treatment. The EPA follows links between pesticides, herbicides and adverse medical effects across various demographics, including: between pediatric cancer and common household pesticides; pesticides and Parkinson’s disease; and pesticides and Alzheimer’s disease risks. One example is the herbicide, Atrazine, a known endocrine disrupter that has been linked to sex changes in many male frogs—from male to female—and the “emasculation” of three-quarters of frog populations. Atrazine’s worldwide ubiquity could likely be linked to a global decline in the frog and amphibian populations, which is having adverse impact on world ecology.
- Retarded neurobehavioral development: Studies in Denmark and USA have suggested that children born in polluted areas have some impairment of memory and intelligence. Prenatal exposure to phthalates has also been linked to problem behavior in children. A 2010 collaborative study by Mount Sinai, Cornell University and U.S. Center for Disease Control and Prevention connects attention deficits and aggressiveness in children to levels of phthalate exposure in the womb.
"The number of chemical combinations that the Earth's living organisms are exposed to is enormous," says Thomas Backhaus, researcher at the Department of Plant and Environmental Sciences and co-author of the EU report. "Assessing every conceivable combination is not therefore realistic, and predictive approaches must be implemented in risk assessment. We need guidelines on how to manage the chemical cocktail effect so that we can assess the risks to both humans and the environment."
EU environment ministers have urged the European Commission to step up its risk assessments and amend legislation on the combination effects of chemicals. They have produce 2010 recommendations on how combinations of hormone-disrupting substances should be dealt with on the basis of existing legislation, and will be assessing suitable legislative changes in 2011.
The world will be watching.
For more detailed information on endocrine disruptors, visit http://www.epa.gov/endo/pubs/edspoverview/whatare.htm and http://www.niehs.nih.gov/health/topics/agents/endocrine/
Sources:
The study, State of the Art Report on Mixture Toxicity, published by the EU's Directorate-General for the Environment.
http://ec.europa.eu/environment/chemicals/effects.htm.
Lynette Summerill, is an award-winning journalist who lives in Scottsdale, Arizona. In addition to writing about cancer-related issues, she writes a blog, Nonsmoking Nation, which follows global tobacco news and events