We have poisoned our Environment Everyday, we, in a personal and collective way, may have realized that there are many among us who have health situations of which our grandparents had never heard. Bottled water - Imagine- paying for water! Skin allergies, asthma, higher cancer rates. Fertility Clinics - who would have believed 20 years ago that this would be a booming industry? We all have known someone who has had some difficulties with pregnancy. Many of the problems that we are encountering today did not exist before the widespread use of DDT, PCB's and NPE's.

How is Toxicity measured? Toxicology is the study of poisons. One of the first compounds regarded as a poison was arsenic. It was the chief agent of poisoning crimes from the middle ages right up to the 20th century. In 1849, a toxicology program was begun at the University of Ghent in Belgium as a small part of pharmacy and chemistry studies. Since WW2 with the explosion of synthetic materials such as pesticides and detergents, it has necessarily grown as a scientific endeavour and is now its own discipline.

Instruments of Measure The oldest and most crude instrument of toxicity is the LD50 (Lethal Dose 50%). This is the amount of a substance that can be eaten or ingested before 1/2 of the animals in the group die. Although the concept has been around for a century, it is not a very realistic representation as few people will ingest a large quantity of a toxic substance, no matter how hungry they may be. Occupational Health inspectors use a toxicity indicator called TLV (Threshold Limit Value). By monitoring the air in certain industries, and linking the statistics of their workers' health compared with the general public, they can determine the risk limits of personal exposure by inhalation. A recent example tracked use of the industrial solvent Ethylene Glycol in the circuit board production at IBM where the rates of miscarriage were dramatically greater than average. The most recent advance in toxicology measurement is the concept of Lethal Concentration 50% (LC50) In a cubic metre enclosure, animals are exposed to different concentrations of the studied compound. The risk level is then determined by the concentration that kills 50% within 4 hours. The lungs are truly the greatest entry route into the body as we exchange (>30L/min) air gases & volatiles into our circulatory system. Future measurement will be done without killing animals by using molecular techniques to identify specific cellular disruption. One of the best ways to determine the relative safety of a product is to read recommendations on its MSDS describing how it should be disposed of. If, for example, there is a declared fine from a state or provincial environmental body (Sewer Laws) for dumping the product down drains - then it is probably acutely toxic. As examples, a disinfectant containing the synthetic o-phenyl-phenol (OPP) is only permitted at a maximum of 1 ppm (part per million) and for detergents containing NPE's (nonyl phenol ethoxlate) it is only 0.04 ppm. If a product label says "Domestic Disposal", you can then feel comfortable.

Hormone Disruptors Rachel Carson warned us in Silent Spring (1962) about the rapid ecological upheaval that was being caused by the widespread use of synthetic chemicals, especially in agriculture and forestry. The latest understanding in toxicology is about the ability of some chemicals to mimic hormones in living organisms. This field of study is about subtle genetic changes brought on by hormone disrupters. This is in contrast to the widely held notion that if a compound is toxic it will knock you out with a heavyweight punch. Hormonal activity in animals is regulated by the endocrine system. These hormones act like messengers relaying information to cells about how and when to grow, divide or die. When disrupted by chemicals, transgenerational genetic damage can occur. In-utero exposure to toxic compounds may sometimes cause birth defects, but will be more likely to emerge later in life at the time of maturity and reproductive prime. Synthetic compounds such as NPE's (Nonyl Phenol Ethoxylates) mimic hormonal structure and function, blocking important receptor sites in cells. What is especially amazing about these detergents (which have been banned by ALL European countries) is that it takes only one tenth of a part per million to cause reproductive damage in Salmon. The Salmon stocks are low due to intense pesticide use in agriculture and detergent use in the pulp and paper industry.

Plastic Toxics Many man-made products have entered the marketplace with little or no toxicity testing. This is particularly true of plastic materials. In Dentistry, the most serious toxics (hormone disrupters) are the phthalates (DBP Dibutyl phthalate and DOP DiOctylPhthalate). These have been used as plasticizers for denture and soft lining materials. Over time they leach out into the oral cavity. It is advisable to obtain an MSDS on the products used in the laboratory to ensure these plasticizers are not part of your prosthesis. Composite resins have recently been noted to contain toxics. BisPhenol A, the core of the Bowen resin, along with Triethylene Glycol Dimethacrylate are mostly inert when fully polymerized, yet the uncured resin could have serious toxic effects.

Heavy Metals Industrial sources have added three major metal toxics - Lead, Cadmium and Mercury to our rivers and lakes. These metals and their salts have been shown to be hormone disrupting and also cause neurological damage. Cadmium has been the raw material for yellow and red pigments used in porcelains and Denture Bases. Newer, safer pigments have been available for over 15 years, yet there are still some manufacturers who persist in using Cadmium. Almost 1/3 of the Mercury found in the Great Lakes basin can be traced to Dental origins. Because of this there will be increasing pressure on Dental Clinics to retrieve amalgam before it enters the wastewater. Finally, attention should be paid to minimize, replace or recycle any lead found in X-ray films and in older plumbing solder joints.

Carcinogens / Teratogens The most common carcinogen that Dental staff have been exposed to, other than Cigarette smoke, is Formaldehyde. It is the most toxic and carcinogenic of the aldehyde family and is found in many Chemical Vapour sterilizer solutions. Many companies have taken steps to eliminate it from their formulae, and most Dental offices vent the sterilizers outside. Vapours from o-phenyl-phenol have been linked to throat cancer. The most common teratogen found in Dentistry is Ethylene Glycol, an industrial solvent that makes up about 5% of many spray disinfectants or the equivalent of 50,000 ppm.

What can you do? If you are concerned about long term health issues, ask for an official letter from your product supplier confirming that their product does not contain any hormone disrupting chemicals, specifically Nonyl Phenol Ethoxlyate (NPE) or teratogens (Ethylene Glycol) or carcinogens (o-phenyl-phenol). Insist on a current (<3 years) Material Safety Data Sheet (MSDS). Both the EPA and Health Canada have placed these chemicals on their priority list for rapid reduction in the marketplace.