Persistent environmental pollutants responsible for obesity epidemic Prof. Joe Cummins. A fully referenced version of this report is posted on ISIS members website and is otherwise available for download here
Metabolic diseases and obesity are on the increase over the last decades. In France, the proportion of population overweight or obese rose 12 % between 1997 and 2003, from 36.7 to 41.6% . In the United States, the prevalence of obesity was 32.2% among adult men and 35.5% among adult women in 2007-2008 ; and obesity in adolescence was significantly associated with increased risk of severe obesity in adulthood . In 2011, a national cohort study of infants and toddlers in the US found that nearly one-third were overweight or obese at 9 months and 2 years of age .
Obesity is associated with cardiovascular disease and diabetes; while epidemiological data demonstrate a link between obesity and multiple types of cancer. Obesity disrupts the dynamic role of the adipocyte (fat cell) in energy homeostasis, resulting in inflammation and alteration of metabolic signalling. In addition, obesity causes secondary changes related to insulin signalling and lipid deregulation that foster cancer development . The growing epidemic of obesity has alarming health consequences; hence the treatment of obesity deserves serious consideration. In the past, genetic, sociological, and psychological factors have been discussed; but within the last decade, it has become obvious that chemical pollution may be an unexpected and important factor in the obesity epidemic.
The obesogen hypothesis has been put forward for about a decade; it postulates that certain chemical pollutants can promote obesity by altering homeostatic metabolic set-points, disrupting appetite controls, perturbing lipid homeostasis to promote adipocyte (fat cell) hypertrophy (cell enlargement), or stimulating adipogenic pathways that enhance adipocyte hyperplasia (increase in cell number) during development or in adults .
Obesogens are environmental chemicals that cause people to become fat analogously to carcinogens for cancer, mutagens for genetic mutations, and teratogens for birth defects. Obesogens are functionally defined as chemicals that inappropriately alter lipid homeostasis and fat storage, alter metabolic set points, disrupt energy balance or modify the regulation of appetite and satiety to promote fat accumulation and obesity. Obesogens appear to be active in all vertebrates.
Environmental obesogen pollutants
The chemical pollutants implicated in the fat epidemic are widely recognized, for the most part, as being endocrine disrupters. The main obesogens include tributyltin (TBT), triphenyltin (TPT), bisphenol A (BPA), perfluoroalkyl compounds (PFCs) and polybrominated diphenyl ethers (PBDEs) [7, 8]. TBT and TPT are used for wood preservation, as antifouling pesticide in marine paints, antifungal in textiles and industrial water systems such as cooling tower and refrigeration water systems, wood pulp and paper mill systems, and breweries. Bisphenol A is used primarily to make plastics, and products using bisphenol A-based plastics have been in commerce use since 1957. PFCs are a group of chemical surfactants most notably used in non-stick and stain-resistance applications. They are major persistent organic pollutants. PBDEs are used as flame retardants; like other brominated flame retardants, PBDEs have been used in a wide array of products, including building materials, electronics, furnishings, motor vehicles, airplanes, plastics, polyurethane foams, and textiles.
Along with the persistent organic pollutants (POPs) listed above are a number of well-known POPs including Dichlorodiphenyldichloroethylene (DDE), formed by the loss of hydrogen chloride (dehydrohalogenation) from DDT, Polychlorinated biphenyl (PCB), a very persistent pollutant derived from electrical equipment but now phased out, and combustion products polychlorinated dibenzodioxins and polychlorinated dibenzofurans which have also been implicated in weight gain. In addition, the old pesticides hexachlorobenzene, hexachlorocyclohexane, and oxychlordane all caused weight gain. The plastics additive phthalates used in a large variety of products, from enteric coatings of pharmaceutical pills and nutritional supplements to viscosity control agents, gelling agents, film formers, stabilizers, dispersants, lubricants, binders, emulsifying agents, and suspending agents, have also been tested and found to increase body size and the size of progeny of the exposed parent . Apart from POPs, certain pharmaceutical drugs are also implicated as obesogens. The known environmental and pharmaceutical obesogens and their regulatory status are presented in Tables 1 and 2; it is very likely that the lists will grow [7, 9]….”