Electric versus disposable toothbrushes

G Magazine

We pit disposability against energy usage in the humble daily ritual of teeth cleaning.

Toothbrush versus

Credit: iStockphoto

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How much thought do you give to the seemingly innocuous plastic tool that lurks in your bathroom? With dentists recommending you change your toothbrush every three months, it is probably the most regularly replaced item in your personal hygiene arsenal.

Australians discard around 30 million toothbrushes each year, adding 1000 tonnes of plastic to landfill. Just one person can create four kilograms of waste from disposable toothbrushes during a lifetime.

Electric toothbrushes are often touted as more eco-friendly than disposables because only the head needs to be replaced, which means less landfill. But the regular plastic disposable has the advantage of using no electricity. Recently, compostable bamboo toothbrushes have been touted as the ultimate in eco-dental care. So which of these options is really theleast harmful to the planet - electric, disposable plastic or bamboo?

Getting a handle on manufacture

The handles of most manual toothbrushes are polypropylene plastic and the rubber grips made from styrene-based thermoplastic elastomers. The bristles are made from nylon and anchored to the brush with silver nickel wire.

During manufacture, the plastic handle is formed by injection moulding, and the various components are irreversibly co-moulded together.

As with most plastics, polypropylene and nylon are sourced from non-renewable petroleum and their manufacture is resource-intensive.

The materials used in rechargeable electric toothbrushes are similar, with additional components including a
plastic base, plug and power cord. The internal motor, which moves the bristle head, can contain nickel- and chromium-bearing alloys.

Electric brushes are commonly powered by an internal rechargeable nickel-metal hydride (NiMH) or nickel-cadmium (NiCa) battery. Both have environmental impacts over their lifespan.

An estimated 50 per cent of the total eco-costs of a manual toothbrush, and 60 per cent of the lifetime energy requirements for an electric toothbrush, are incurred during the manufacture and distribution phases, compared to the usage and disposal phases.

In comparison, the handle of bamboo brushes are made from moso bamboo, a rapidly renewing plant which requires little water. However, in a life cycle analysis from researchers at Delft University of Technology in the Netherlands, 20 per cent of the eco-costs of a bamboo product came from shipping the bulky raw bamboo stems from China.

Shipping from China to Australia is a considerably shorter distance than shipping to Western Europe. James Wilson, spokesperson for the Australian-owned Environmental Toothbrush company says: "Our bamboo is grown in China, but close to the manufacturing plant. Shipping the finished product keeps our carbon footprint down."

A carbonisation finishing process, which provides water resistance and prevents the growth of microbes on the toothbrush, also increases the eco-costs of bamboo.

The bristles of the bamboo brush are made from a nylon 4 blend. Wilson explains,"We tried to find a natural bristle, but only boar hair was available and we wanted to avoid using animal products."

Energy use

Of the three options, only the electric brush incurs energy costs while performing its intended task – brushing your teeth. Research from Bath University, England, found that powered brushes use around 0.072kWh/day, equivalent to the energy use of a toaster.

Many manufactures also recommend leaving your toothbrush on constant recharge, but a study conducted by the University of California, Berkeley, shows electric toothbrushes draw almost as much power to maintain charge (1.58 W) as when charging (1.65 W).

Constant recharging can also wear out the battery, meaning you have to replace either the battery or the whole appliance, depending on the product design.

Disposal dilemma

Although the individual materials used to make plastic toothbrushes, manual and electric, are recyclable, irreversible bonding during manufacture makes recycling impossible.

A manual toothbrush weighs around four times that of an electric toothbrush head and therefore produces waste equivalent to a year's worth of replacement heads. As dentists now believe a larger handle aids brushing technique, manual toothbrushes have become much larger in recent years, considerably increasing the amount of plastic that ends up in landfill.

Like all plastics, toothbrushes find their way into waterways and oceans where marine creatures can mistake them for food; recently a female albatross on Hawaii was observed trying to regurgitate a plastic toothbrush for a chick.

Rechargeable batteries are considered hazardous waste because they can leach toxic chemicals into landfill. Many councils offer collection or drop-off services. Plastic and metal components of NiCa and NiMH batteries can be recovered and recycled. Visit www.recyclingnearyou.com.au to find out about battery recycling in your region, through councils and waste disposal companies.

In comparison, bamboo brushes break down into compost, leaving no residue, including the nylon bristles. Japanese researchers have shown that nylon 4 breaks down in compost within four months, while nylon 6 does not.

Packaging is also a consideration. Conventional manual toothbrushes, and replacement heads for electric toothbrushes, are commonly packaged in a 'blister pack' of polyvinyl chloride (PVC) and cardboard, while bamboo toothbrushes come in a cardboard box.

The verdict

It's a close call between the two traditional competitors. While the electric toothbrush produces less landfill, the environmental costs involved in the manufacture and disposal of additional components and energy use make it as planet-polluting as the manual.

The leader in all fields is, of course, the bamboo brush. With respect to materials, manufacture and waste, it streaks ahead of the plastic pretenders. You can currently buy these from The Environmental Toothbrush Company.

In terms of oral health, a 2003 review of scientific studies comparing the effect of six types of powered brushes with manual brushes found no clear advantage to using five of the powered toothbrush types. However, 'rotation oscillation' brushes significantly reduced plaque and gingivitits. If you can't bear to be parted from your plug-in, minimise your impact by recharging judiciously and buy replacement heads in multi-packs to reduce packaging waste. Old manual toothbrushes are also a great cleaning tool for hard-to-reach spots around the home.