Tuesday February 26, 2013
Chemicals in everyday items pose a health hazard
By TAN CHENG LI
Common chemicals to blame for a host of ailments.
WE are making ourselves, and our children, sick, through widespread use of chemicals which can interfere with hormones in our bodies. Latest studies have found clearer associations between exposure to substances dubbed as “endocrine disrupting chemicals” (EDCs) and the surge in modern-day ailments such as breast and prostate cancers, reduced human fertility, birth deformities, early puberty and developmental disorders in children such as autism and attention deficit hyperactivity disorder.
A study commissioned by the United Nations Environment Programme (UNEP) and the World Health Organisation (WHO) points to three strands of evidence which fuel concerns over EDCs: the high incidence and rise in many endocrine-related disorders in humans; observations of endocrine-related effects in wildlife populations; and laboratory studies which linked chemicals with endocrine disrupting properties to certain diseases.
“We live in a world in which man-made chemicals have become part of everyday life. It is clear that some of these chemical pollutants can affect the endocrine (hormonal) system and interfere with important developmental processes in humans and wildlife species,” declared the State of the Science of Endocrine Disrupting Chemicals 2012, released last week as a policy guide for governments.
The report, developed by a global team of experts grouped under the Inter-Organisation Programme for the Sound Management of Chemicals (IOMC, a multi-UN-agency body established in 1995), is the most comprehensive compilation on EDCs to date.
Human health depends on a well-functioning endocrine system to regulate the release of certain hormones that are essential for functions such as metabolism, growth and development, sleep and mood. EDCs – pervasive in many household and industrial products – can alter the functions of this hormonal system, leading to adverse effects on human and wildlife health. The report reveals some stark health statistics indicating the growing trend of many endocrine-related diseases and disorders:
> 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 (cryptorchidism) and penile malformations (hypospadias) in baby boys are up.
> Higher incidence of adverse pregnancy outcomes, such as pre-term birth and low birth weight in many countries.
> Behavioural and learning problems such as dyslexia, mental retardation, autism and attention deficit hyperactivity disorder in children now affect 5% to 10% of babies born, while autism spectrum disorders now affect almost 1% of children.
> The global rates of endocrine-related cancers (breast, endometrial, ovarian, prostate, testicular and thyroid) have increased over the past 40 to 50 years.
> Girls are developing breasts at a younger age; this is a risk factor for breast cancer.
> The prevalence of obesity and type 2 diabetes (EDCS can interfere with the body’s metabolism).
> The incidence of paediatric leukaemia and brain cancer has risen.
Pervasive and persistent
The emergence of these disorders over such a short time means that genetic factors can be ruled out, says the report. “Environmental and other non-genetic factors, including nutrition, age of mother, viral diseases and chemical exposures, are also at play, but are difficult to identify. Despite these difficulties, some associations (with EDCs) have become apparent.”
It says everyone is exposed to these often little-studied or understood compounds as they are circulated globally through natural processes (ocean and air currents) as well as through commerce.
“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. The vast majority of chemicals in current commercial use have not been tested at all.”
Some EDCs occur naturally – in metals such as lead, cadmium and methymercury and in chemical elements such as arsenic. Synthetic EDCs can be found in a large variety of materials and goods, including pesticides, packaging materials, pharmaceuticals (contraceptive, hormone therapies, lipid regulators, beta-blockers, anti-depressants), flame retardants (used in mattresses, sofas and textiles), electronics, plastic additives, plastic toys, personal care products, household cleaners and construction materials.
EDCs also enter the environment through industrial and urban discharges, farm run-offs, untreated sewage and inefficient coal power plants.
Humans absorb the harmful substances when they ingest contaminated food, dust and water, inhale gases and particles in the air, and through skin contact. Women can transfer the EDCs to a developing foetus through the placenta and to a child through breast milk.
Children have higher exposures to EDCs because of their hand-to-mouth activities. Whereas in adults the effect of the EDC diminishes when it is withdrawn, exposure during development stages (in utero and infancy and early childhood) can have permanent effects if the exposure occurs during the period when a specific tissue is developing. These effects may only become visible decades later.
The report flags concern over the many personal care products (cosmetics, lotions, shampoos, toothpaste, soaps) containing EDCs such as galaxolide (used as a fragrance), cyclic methyl siloxanes (solvent), parabens (preservatives) and phthalate (stabilising agent).
Electronic waste poses another threat as the plastic and metal components contain EDCs such as lead, cadmium, mercury, polychlorinated biphenyls (PCBs) and the plastic additive, phthalate.
Epidemiological evidence has associated several commonly used EDCs, including PCBs, flame retardants, phthalate, bisphenol A and perfluorinated chemicals (chemicals used to make materials stain- and stick-resistant), with reduced serum thyroid hormone levels in humans. Impaired thyroid function is associated with neurobehavioural disorders, including reduced IQ, attention deficit hyperactivity disorder and autism.
The report also raises similar concerns on the impact of EDCs on wildlife. In Alaska in the United States, exposure to such chemicals may contribute to reproductive defects, infertility and antler malformation in some deer populations.
Population declines in species of otters and sea lions may also be partially due to their exposure to diverse mixtures of PCBs, the insecticide DDT, other persistent organic pollutants, and metals such as mercury. Effects shown in wildlife or laboratory animals might also occur in humans if they are exposed to EDCs at a vulnerable time and at concentrations leading to alterations of endocrine regulation.
Meanwhile, bans and restrictions on the use of EDCs have been associated with the recovery of wildlife populations and a reduction in health problems.
Gaps in knowledge
The report says much remains unknown about EDCs and this hampers progress towards better protection of the public and wildlife. Because only a small fraction of the thousands of synthetic chemicals in existence have been assessed for endocrine disrupting activity, and because many chemicals in consumer products are not identified by the manufacturer, we have only looked at the “tip of the iceberg”.
The experts warn that the disease risk from the use of EDCs “may be significantly underestimated” as we are simultaneously exposed to many EDCs but the effects of this multiple exposure have not been adequately studied. Also, it is likely that “harmful effects in humans and wildlife are being overlooked” as validated tests currently available capture only a limited range of the known spectrum of endocrine disrupting effects.
“Worldwide, there has been a failure to adequately address the underlying environmental causes of trends in endocrine diseases and disorders. Healthcare systems do not have mechanisms in place to address the contribution of environmental risk factors to endocrine disorders,” says the report.
To get a better grip on the harmful effects of EDCs, it recommends the following:
> Testing: More comprehensive testing methods are required to identify other possible endocrine disruptors, their sources, and routes of exposure.
> Research: More scientific evidence is needed to identify the effects of mixtures of EDCs on humans and wildlife (mainly from industrial by-products) to which humans and wildlife are increasingly exposed.
> Reporting: Many sources of EDCs are not known because of insufficient reporting and information on chemicals in products, materials and goods.
> Collaboration: More data sharing between scientists and between countries can fill gaps in data, primarily in developing countries and emerging economies.
“We urgently need more research to obtain a fuller picture of the health and environment impacts of endocrine disruptors,” said Dr Maria Neira, director for public health and environment at WHO.