Vinyl Gloves: Protection or Poison

Published: 4 Nov 2003

By Tom Wood Jr., Sr. Industry Analyst, Environmental Technologies

(Note: ALL common commercial plastics and other polymers, including rubber, contain additives, the safety of which are not the subject of this particular article)

Despite the estimation that less than 1 percent of the US population suffers from latex protein allergies, concern has been sufficient to generate an entire and quite lucrative market for nitrile replacement gloves. Even adhesive bandages are now being advertised as "latex free". What has not been so widely publicized though are the issues surrounding polyvinyl chloride (PVC) and its usage in various consumer and industrial applications, including gloves.

 

What is PVC?

Polyvinyl chloride is a polymer, or large chain-like molecule, made up of repeating ‘monomer’ units of vinyl chloride. Vinyl chloride (VC) is both a known carcinogen and a regulated chemical whose production capacity has almost doubled over the last 20 years, currently running at 27 million tons/year worldwide. The VC monomer does not, theoretically, occur in PVC polymer produced with perfect quality control. This highly toxic compound has, however, been found to be a trace component of PVC. There have been reports of VC in drinking water that has been standing for a period of time in PVC water pipe.

Commonly referred to as Vinyl, PVC is exceeded only by polypropylene and polyethylene in the variety of products that are made from it. PVC is found in car interiors and trim, wall coverings, floor tiles, window frames, siding, water and sewer pipes, shrink wrap, packaging (including blister packs and food wraps), medical equipment (tubing, transfusion bags, blood storage bags, respiration tubes), electric and electronic cable insulation, textiles (as trim and complete garments), gloves (medical and food preparation), toys, and numerous other products (Chart 1).

Click to enlarge
Click to enlarge

PVC can be a tough, rigid material, or soft and flexible, depending on the use of additives. It is denser than other plastics, and so preferred by food processors for packaging. It has also proven to be the most effective material for the storage of red blood cells, as blood lasts twice as long in PVC bags than it does in any other container, including glass or other plastics. Its additives include anti-oxidants (heat and light stabilizers) to extend the life of the plastic, and softeners or plasticizers to allow a precise degree of flexibility. All polymers, in a perfectly pure state at room temperature, are completely non-toxic since they are nearly inert and insoluble. All commercial polymers, however, require a variety of additives. They all undergo degradation and decomposition when exposed to heat during formulation or molding into products. They also tend to break down when subject to the mechanical stress of molding or extrusion. Finally, all products made from polymers are degraded by the light, heat, stress, and air pollution encountered in everyday use. For this reason, one or more stabilizers are required for each type of plastic.

Stabilizers in PVC

PVC has the special problem of forming HCl (Hydrochloric Acid) when it degrades, causing a chain reaction that proceeds rapidly to complete its loss of strength. The stabilizers for PVC have, therefore, primarily been metal salts that could react with the HCl. These have included Lead, Cadmium, Barium, Calcium, Zinc, and organic Tin compounds, the first two of which are known and highly publicized poisons. Although it appears that Cadmium is not used much any more, there are varying accounts concerning the prevalence of Lead as a stabilizer. According to an Australian document dated 1996, it is still quite widely used. Lead is not used where a clear Vinyl is required. Window covering, food packages, tubing, etc, use Organic Tin Compounds (Organotins) or Calcium/Zinc. There have been some findings linking Organotins to reproductive and immune system problems. A compound similar to ones used in PVC is used in marine antifouling paint, and has been blamed for the destruction of marine life in harbors. Consequently, Australia has banned the use of this Organotin.

Stabilizers are not chemically bound to the PVC polymer chains. Whether mixed in during formulation or into the melt during manufacturing, stabilizer molecules are held in place when the melt freezes, like objects in an ice cube. Metal salts (like lead carbonate) don't readily mix into an organic polymer, and so tend to clump and migrate when the polymer is heated, or in surface areas when subjected to weathering and stress. These stabilizers tend to accumulate on the surface during normal use, especially if the product is exposed to heat, stress, or light, particularly direct sunlight. The leaching of lead from new PVC pipe, for example, has been cited.

Phthalate Plasticizers

The PVC polymer chains form an attraction to one another, which produces a very rigid plastic. When a soft or flexible plastic is required, a softener or plasticiser is added to allow the chains to slide against each other, providing the desired flexibility. Although a range of chemicals are used as softeners, phthalate esters (phthalates) are by far the most commonly used in PVC. DEHP (Di-Ethylhexyl Phthalate) has been the most commonly used, but in the past few years, DINP (Di-Isononyl Phthalate) has also been used.

Phthalates do not bind to the PVC, remaining present as a freely mobile and leachable phase in the plastic. As a consequence, phthalates are continuously lost from soft PVC over time. DEHP is nearly insoluble in water, but highly soluble in fats and oils. When used in medical tubing, it has been found to accumulate in blood, lung, and liver tissue, as well as in fat. In fatty foods, such as butter, cheese, and prepared meat products packaged in PVC, significant amounts of DEHP or DINP have been found in surface layers. DEHP does not vaporize easily at room temperature, but does migrate out of the plastic as a vapor over 30° C (86° F), and has been found in the air stream of medical respiratory tubing. Under relatively slight pressure, phthalates will exude from PVC. As little as 1.4 lb/sq. inch can result in the loss of 30 percent of the plasticizer.

DEHP is believed to damage the reproductive systems of animals. Experiments on animals have shown that DEHP reduces the production of sperm. Thus far, phthalates show almost no toxicity in adult humans in acute (short term) doses. The cumulative nature of phthalate toxicity, however, is suspected to be much more pronounced when ingested chronically (long term). The common availability of phthalates in the consumer environment causes inevitable chronic ingestion for almost all modern industrial consumers. It has been suggested that chronic intake and accumulation to a deleterious level may require 30 to 40 years. As extensive use of PVC materials in homes, medical care, and as food packaging material started only during the 1960’s, an evaluation of chronic human toxicity can only now begin to be conducted and assessed. The fear is that young infants, who do not metabolize phthalates as well as adults, are at greater risk of harm.

Although less well researched than DEHP, DINP shows similar toxicological properties in laboratory animals. When purchased for laboratory use, DINP is labeled with a number of hazard phrases, including "harmful by inhalation, in contact with skin, and if swallowed", "possible risk of irreversible effects" and "may cause cancer". In contrast, toys containing up to 40 percent, by weight, DINP in a readily leachable form are frequently labeled "non toxic". The properties of other alternative plasticizers are equally unsavory (Chart 2).

Conflicting Concerns

Various organizations with obviously conflicting perspectives and agendas have debated both sides of this issue for some time, often citing the same sources for their justification. Opponents of phthalates quote Canada’s federal health department, Health Canada, as concluding that "the status quo is not an acceptable option." Proponents say that Health Canada has classified DEHP as "unlikely to be carcinogenic to humans." Health Canada’s own recent reports, however, accede that "there are very few human data from which to characterize the toxicity of DEHP. Therefore, the evaluation of human risk from medical exposures (most intravenous procedures) must be extrapolated from studies in experimental animals where species differences in metabolism are important considerations. Uncertainties exist in the performance of such extrapolations."

Manufacturers have consistently argued that there is no evidence that anyone has been harmed by phthalates. This is undoubtedly true, as no study has ever examined the impacts of phthalate exposure on the developing human male reproductive tract. Lack of evidence, therefore, can hardly be used as evidence of safety or the lack thereof.

Perception is Reality

One thing is certain. There is enough ‘reasonable doubt’ being raised worldwide to make the perception of phthalates as being unsafe a reality. The Japanese Health and Welfare Ministry kept secret a report compiled in February 2001 that revealed a high concentration of DEHP in boxed lunches sold at convenience stores. The substance is believed to have permeated the food via plastic gloves worn by the workers who prepared the boxed lunches. While withholding the information from the public, the ministry’s Food Chemistry Division secretly released the data to related industries, urging them to deal with the problem. When the report was finally revealed in July of that year, the minister ordered the food industry and local governments to refrain from using gloves containing DEHP when handling food. Since then, users have switched to nitrile or latex gloves. TOWA, a leading Japanese glove manufacturer, has even developed a PVC glove that does not contain the phthalate ester, which may or may not prove to have the same inherent VC drawbacks.

In addition, the Danish EPA has recently demonstrated that the leaching of phthalates from teething toys can be substantial. This has been supported by similar studies in other countries and has led, in some cases, to recommendations that certain toys be withdrawn or even that the use of soft PVC in toys for young children be discontinued.

And as recently as this week, the state of California will add DEHP to the Proposition 65 list of chemicals known to cause birth defects or reproductive harm. Kaiser Permanente, Miller Children’s Hospital in Long Beach, Lucile Packard Children’s Hospital at Stanford University, and John Muir Medical Center in Walnut Creek are all phasing out PVC medical devices from their NICUs.

The Occupational Safety and Health Administration (OSHA), when contacted for this report, indicated that the agency responsible for approval for the marketing of medical gloves is the Food and Drug Administration (FDA). The FDA apparently recently held a meeting to gather public comments regarding food service gloves. The response from the director of the FDA Center for Devices and Radiological Health was, "We are not aware of any ban in Europe, but Japan has banned PVC gloves for food handling. The Center has not tried to ban PVC medical gloves because the risks of DEHP are based on animal studies and when the data is extrapolated to humans, the exposure dose is far below the tolerable intake (TI). The TI is defined as the dose of a compound that is not expected to result in adverse effects. However, if Japan has banned PVC gloves for food handling, the Center for Food Safety and Nutrition should be consulted for their response" (Such response is anticipated and hopefully forthcoming as of this writing). They conclude by stating that, "There are also groups that would find the most probable substitute for PVC gloves to be NRL gloves. They would argue that natural rubber allergens are a known human hazard." This is precisely why the state of Rhode Island recently made it illegal for food handlers to wear disposable gloves made of natural rubber latex, making Vinyl its most likely alternative. It remains to be seen which is the worst alternative!

If you would like to know more about Frost & Sullivan’s capabilities in the Health & Safety arena, please contact Michael Valko at mvalko@frost.com.

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