Cancer, Children and Rubber Tires

Over 1 billion tires are manufactured annually, making the tire industry the majority consumer of natural rubber. Pneumatic tires are manufactured according to relatively standardized processes and machinery in around 450 tire factories in the world. (1)

Natural rubber comes from tropical plants.  Major producing countries are Malaysia, Indonesia and Thailand.  Both small and large rubber plantations supply the liquid latex.  Many of the large tire companies have vast holdings in South East Asia. (2)

Natural rubber is mainly used in radial tires and in blends with various synthetic elastomers where its use improves weathering qualities.

Radial tires were first developed by the Michelin company of France in the 1930′s. This company, founded by two brothers in 1863, began to sell radial tires in the United States in the 1960′s.

By 1980, the company had four plants in the Unites States and by the late twentieth century had become one of the world’s biggest producers of automobile tires. (3)

Even in economic depression when net profits fell 14.2% year on year, Michelin still managed to record a profit of EUR3.51bn ($US4.62bn) in the first quarter of 2009. (4)

This was helped by its cash purchase of $69 million for Oliver Rubber Co, from Cooper Tire & Rubber Co. in 2007, which produces tread rubber and retreading equipment, and now operates as a subsidiary of Michelin North America Inc. (5)

Michelin has a sustainable development approach called; “Michelin Performance and Responsibility”, which is fully integrated into the Group’s action plans and projects.

According to Michelin, this overall performance is based on five fundamental values:

(1) respect for customers;

(2) respect for people;

(3) respect for shareholders;

(4) respect for facts; and

(5) respect for the environment.

All Group decisions are taken in light of these values. (6)

There’s no doubting points 1 and 3.  If it didn’t provide its customers with a quality product then sales would be low and a healthy profit would not be possible.  Share holders would not be happy.  Their happiness is reflected in the increase of over 50% annual share performance shown below.

Year-to-date range (2009): 02/11/2009 10:39

	Previous year close	Year high	Year low	Annual performance
Michelin (€)	37,57	58,67	22,69	+50,57 %

But what about points 2 and 5?  Respect for the environment/Respect for the people.

‘It is our responsibility to provide our customers with ever more environmentally-friendly products and services. Accordingly, our permanent innovation policy focuses on enhancing the environmental performance of mobility.’

How is it faring on this pledge?

The vehicle can seat five, features two boots, sufficient driving range for long trips (between 150 and 400 km depending on the modular energy source). It consumes five times less energy in city driving and emits up to 20 times less CO₂.

The new underbody design makes the vehicle lighter, thereby reducing energy consumption. Well-to-wheel CO2 emissions are less than 15 grams per kilometer when the car runs on electricity generated by hydroelectric, photovoltaic, wind or other clean power sources.

The first vehicles should be available for professional drivers, fleets and municipalities in 2010. The general public may have to wait an extra year. The current price target is being reported as between €20,000 ($27,344) and €25,000 ($34,180).

Well, these seem positive steps for the environment.  But are there any negatives?

Perhaps one major issue that is often under reported is how the tire industry as a whole is having an increasingly negative effect on the environment.

One way to gauge the negativity of a product is to see what mechanisms and chemicals are involved in the process of production and what effect it has on its workers.

Tire making involves a complex blend of materials and assembly processes to manufacture the thousands of different products used on equipment, ranging from bicycles to earthmovers.

A typical tire includes dozens of different components, using more than one hundred primary raw materials that must be precisely processed and assembled to achieve the right balance between many competing factors: grip, energy efficiency, handling, comfort, and noise, to name but a few.  (7)

A review of more than 50 different chemicals used in making tires showed that many have already been well characterized by their manufacturers.

However, some of the materials used in tire production have not been fully characterized in terms of their chemical and/or biological properties, as is the case with other chemicals used in other industries.

Many materials that occur in the work atmosphere in rubber factories are experimental chemicals that can induce or increase the frequency of mutation in an organism (mutagens), or substances or agents that tend to produce a cancer (carcinogens).

These include mineral oils, carbon black (extracts), curing fumes, some monomers, solvents, nitroso compounds and aromatic amines, thiurams and dithiocarbamate compounds, ethylenethiourea, di(2-ethylhexyl) phthalate, di(2-ethylhexyl) adipate and hydrogen peroxide.

However, experimental toxicological information on chemicals that are used or formed in the rubber tire making process is restricted to a small fraction of all chemicals used: most compounds have not been investigated for their possible mutagenic or carcinogenic effects.

Studies that have been carried out using exposure indicators, such as mutagenic activity in urine, thioether excretion and sister chromatid exchange, point to the possibility that rubber workers are exposed to mutagens. (8)

Is there evidence of higher cancer incidence rates amongst rubber tire workers?

Concerns over high cancer rates in the industry have been surfacing for over 50 years.

For example, cancer of the urinary bladder, which was clearly excessive in British rubber workers employed before 1950, was particularly high in jobs likely to entail exposure to aromatic amines. (9)

However, with the withdrawal in 1949 of certain antioxidants containing 2-naphthylamine from the UK rubber industry, led many to believe there was a subsequent decline in excessive bladder cancer incidence .

Nevertheless, the fear has persisted that this hazard could still be affecting men working in the industry today.

Furthermore, suspicions have also arisen that other and hitherto unsuspected excesses of cancer might be occurring.

For example; stomach cancer, consistently elevated in studies of US and British rubber workers, appears to be associated with jobs early in the production line, including compounding and mixing, milling and extrusion. (10)

Lung cancer is positively related to a variety of jobs within the rubber industry.  However, attribution to specific factors in the workers’ environment cannot be made. (11)

Mortality from prostatic cancer was found to be moderately elevated in several studies, and some association was found with compounding and mixing jobs.

In general, the etiology of prostatic cancer is not understood. The only occupational risk factor suggested to date is cadmium; compounds of cadmium are occasionally included in a rubber batch. (12)

A major study by H G Parkes et al that addressed the above issues was reported in the Br J Ind Med. 1982 August; 39(3): 209–220

The study followed 33,815 men, who first started work in the industry between 1 January 1946 and 31 December 1960, up to 31 December 1975.  Its aim was to ascertain the number of deaths attributable to malignant disease and to compare these with the expected number calculated from the published mortality rates applicable to the male population of England, Wales and Scotland.

The findings confirmed the absence of any excess mortality from bladder cancer among men entering the industry after 1 January 1951, but they confirm also a statistically significant excess of both lung and stomach cancer mortality.  A small excess of oesophageal cancer was also observed in both the tire and general rubber goods manufacturing sectors. (13)

Although no clear evidence exists for a comparable bladder cancer excess in pre 50′s U.S. rubber workers, a study by The National Institute for Occupational Safety and Health (NIOSH) compared the number of bladder cancers among workers at a tire and rubber manufacturing plant from 1973 to 1988 with the number that would be expected in a similar population of New York State residents.

NIOSH particularly examined a relationship between exposure of  two suspicious chemicals involved in the tire making process; aniline and o-toluidine and human carcigenic effect.

One of those chemicals, o-toluidine, is known to cause bladder cancer in animals. Therefore, this chemical is thought to be the most likely cause of bladder cancer in workers.  Another chemical, aniline, causes cancer in rats.

They classified all workers who worked in exposed departments between 1957 and 1988 as “definitely exposed” to aniline and o-toluidine.

The number of bladder cancer cases expected in each group was calculated using the rate of bladder cancer in New York State for individuals of similar age and sex.

In this study, 8 cases of bladder cancer were found among workers “definitely exposed” to o-toluidine and aniline, while only 1.2 were expected.

Among workers who were “possibly exposed” to these chemicals there were 4 bladder cancer cases observed and 1.05 expected.

Among workers who were “probably exposed” to these chemicals there were 2 cases of bladder cancer, and 1.29 expected.

Both o-toluidine and aniline are used to make Wingstay 100.  Wingstay 100 has been manufactured since 1957. Aniline is used to make Morfax which has been manufactured since 1970. The two chemicals were used in certain departments at the plant, such as curing.

Tires are molded in a curing machine also known as a vulcanizer, or a press.  Cure is often called vulcanization or cross-linking. It is an intermolecular reaction caused by the introduction of chemicals (usually sulfur and zinc oxide or Morfax) which link or tie independent chain molecules together. (14)

Zinc oxide is not very toxic (poisonous) when you mistakenly eat it. Most of the harmful effects come from breathing in the gas form of zinc oxide at industrial sites in the chemical industry. This leads to a condition known as ‘metal fume fever.’ (15)

Diagnosis of ‘metal fume fever’ can be difficult, as the complaints are non-specific and resemble a number of other common illnesses. When respiratory symptoms are prominent, ‘metal fume fever’ may be confused with acute bronchitis. The diagnosis is based primarily upon a history of exposure to metal oxide fumes. (16)

Any more harmful compounds involved in tire making?

Lets look at nitrosamines.

Nitrosamines are a class of chemical compounds that were reported, in  1956, by British scientists, John Barnes and Peter Magee, to produce liver tumors in rats. (17)

This discovery was made during a routine screening of dimethylnitrosamine that was being proposed for use in solvents in the dry cleaning industry.

Magee and Barnes’ discovery caused scientists around the world to investigate the carcinogenic properties of other nitrosamines and N-nitroso compounds.

Approximately 300 of these compounds have been tested and 90% of them have been found to be carcinogenic in a wide variety of experimental animals.  Most nitrosamines are mutagens and a number are transplacental carcinogens, being able to journey across or passing through the placenta.

Most are organ specific. For instance, dimethylnitrosamine causes liver cancer in experimental animals, whereas some of the tobacco specific nitrosamines, cause lung cancer.

Since nitrosamines are metabolized the same in human and animal tissues, it seems highly likely that humans are susceptible to the carcinogenic properties of nitrosamines. (18)

There is not currently a restricting directive for N-Nitrosamines in the rubber industry, only an environmental guideline which states that the total amount of N-Nitrosamines in the atmosphere must be below 1 μg/m3.

To determine the role of N-nitrosamines in air concentrations around factory workers, 19 factories were measured by area sampling or personal monitoring.

N-Nitrosodimethylamine (NDMA) and N-nitrosomorpholine (NMOR) were found regularly, the air concentrations varying between 0.1 and 380 µg/m3 in personal monitoring.  (19)

The mean concentration was usually in the range of 1 –10 µg/m3.  Several other nitrosamines could be detected in certain production branches.

In retail shops and storage rooms of tires, NDMA and NMOR have also been found in air concentrations. (20)

So there appears to be a potentially dangerous chemical infusion within the tire at manufacturing level.

Once the tire is on the road, what happens when it begins to wear?

Regarding tire wear particles (TWP), the situation is much less clear. The particles themselves are not simply rubber pieces from the tire, but rather an agglomeration of material from the tire along with material from the road and vehicles. (21)

Tire Industry Project (TIP) reveals the assessment of TWP has received little attention.

Some researchers have estimated that these particles constitute 2-10% of the fine particulate matter (PM10) in the air.

Tests are of limited use because of concerns about the techniques used to identify the particles, a lack of standards in analytical techniques, a lack of standard collection methods, as well as seasonal effects.

In short, it will take considerable effort to understand their properties and dispersion in the environment.

Is this a problem?

If the uptake of diesel is incorporated through exhaust fumes bonding to the tires and TWP is breathed in as dust – it could well be.

Diesel exhaust contains over 40 organic chemicals identified by the EPA as Hazardous Air Pollutants (HAPs), also called air toxics, which are either suspected to cause cancer or create other serious health risks.

The organic chemicals that are of special concern include aldehydes, benzene, 1,3-butadiene, and polycyclic aromatic hydrocarbons (PAHs).

It is the PAH’s that are believed to create much of the cancer risk posed by diesel exhaust.  In fact, because diesel exhaust contains so many substances that contribute to both a cancer and noncancer health risks in humans, the EPA considers diesel exhaust to be a mobile source air toxic. (22)

In 1996, 29 billion gallons of diesel fuel was consumed in the U.S; by 2000, this number was up to 35.5 billion. (23)

Another risk could be when the diesel exhaust infused tires are no longer used.

The major problem with tires is they do not last. They have to be changed once the thread is sufficiently worn.

In the United States alone, 300 million tires a year are thrown away—one for every man, woman, and child. (24)

These castoffs are a huge source of automotive-related pollution—the average used tire weighs 22.5 pounds and contains about two gallons of fuel, as well as other combustible carbon compounds.

Dumped into huge stockpiles, tires harbor vermin, contribute to the spread of disease by creating mosquito breeding grounds, and feed huge fires. (24)

In August 1998, a grass fire ignited 7 million tires near the town of Tracy in California’s San Joaquin Valley, sending a plume of soot and noxious gas thousands of feet into the air.

State authorities originally expected the fire to burn for about two weeks, but it endured for two and a half years. Cleanup was completed in 2006, at a cost of $19 million.

Another source of tire stockpiles ignition is spontaneous combustion.

Spontaneous ignition of large stockpiles of tire shred or deep landfill deposits has occurred on numerous occasions. Practical experience suggests auto-ignition normally occurs in large stockpiles (more than 3 meetrs deep).  Finely shredded tires are more susceptible because of the increased surface area available for reaction. (25)

Why shred tires?

Tires are not desired at landfills due to their large volumes and 75% void space, which quickly consumes valuable space. Shredding reduces this void.

Chopping and grinding of tires produces a low density, porous material through which air may percolate. The total surface area of tire chips or crumb particles may also be large compared with the volume occupied. The combination of permeability to air-flow and a high exposed surface area means that a combustible material such as rubber, is potentially susceptible to spontaneous combustion.

Laboratory experiments show that rubber crumb and tire shred are more susceptible to self-heating than cellulosic materials (like hay and straw) in conditions of high ambient temperature.

Why is this significant?

Heat breaks molecular bonds and if these molecules broken are released into the atmosphere during a hot summers day, then they could be potentially dangerous for someone in the vicinity if they are carcengenic.

Are there many people liable to be near crumb rubber?

Apart from being dumped, ground tire or crumb rubber has also found to have other uses. These include:

• Molded rubber products (e.g., carpet underlay, flooring material, dock bumpers, patio decks, railroad crossing blocks, livestock mats, roof walkway pads, rubber tiles and bricks, movable speed bumps).
• New tire manufacturing (up to 10% or higher).
• Brake pads and brake shoes.
• Additive to injection molded and extruded plastics.
• Automotive parts.
• Agricultural and horticultural applications/soil amendments.
• Horse arena flooring.
• Athletic and Recreational Applications

There have been many concerns about health risks to people recently, especially in relation to crumb rubber and athletic and recreational applications.

Synthetic turf fields have been installed in many athletic and playing fields throughout New York City (NYC), the United States and the world. The NYC Department of Parks and Recreation (DPR) began installing synthetic turf playing fields in 1997 with a total of 94 installations  (87 crumb rubber infill fields and 7 carpet-style fields).

Synthetic turf fields are mainly used in NYC parks because they:

• Provide even playing surfaces.
• Have padding that helps prevent injuries.
• Need no watering or mowing.
• Use no fertilizers or pesticides.
• Can be used year-round and in most weather.
• Do not need to be closed to protect or re-sod grass.
• Last a long time with little maintenance. (26)

However, concerns about the the potential for exposure to chemicals found in crumb rubber resulted in New York City department of Parks and recreation (NYC DPR) to request assistance from the NYC Department of Health and Mental Hygiene (DOHMH) .

In response to this request, and with a grant awarded by the New York Community Trust, the DOHMH contracted a private consultant, TRC solutions who ‘actively provide services to large chemical and petrochemical clients’, to lead an intensive literature review focusing on the potential exposures and health effects related to synthetic turf fields and to identify gaps in what is known.

The report found crumb rubber used in synthetic turf systems was made primarily from recycled waste tires.

Direct and indirect methods have been used in studies to determine the presence of Chemicals of Potential Concern COPCs in the crumb rubber.

These studies have found polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), semivolatile organic compounds (SVOCs), benzothiazole, and certain metals in crumb rubber.

They found crumb rubber, or the dust generated from crumb rubber, may be accidentally ingested by placing fingers in the mouth or not washing hands before eating and after playing on the fields.

Young children on the fields may eat the crumb rubber itself. Dust may be breathed in from playing on the field, or vapors that volatilize from the turf may also be inhaled. Some COPCs may also be absorbed through the skin by direct contact.

Children, especially very young children, have many characteristics which make them vulnerable to environmental exposures. Children breathe more air per pound of body weight than adults in the same environment and physical activity adds an additional factor to exposure through inhalation.

Children also engage in hand-to-mouth behavior and very young children may eat nonfood items, such as rubber crumbs while on the fields. The protective keratinized layer of the skin is not as well developed in children and increases dermal absorption of COPCs as well as increasing evaporative loss of water on hot days. Children also have many more years to develop diseases with long latency periods after exposure.

To date, eleven human health risk assessments were identified that evaluated exposure to the constituents in crumb rubber.

These risk assessments have been conducted primarily by state agencies, consultants and industry groups.

The study concluded that for the COPCs in the crumb rubber to be a health concern for users of the fields, users would have to be exposed to high enough concentrations to increase the risk for health effects. And none of the eleven reports identified an increased risk for human health effects as a result of ingestion, dermal or inhalation exposure to crumb rubber.

These findings were also supported by The U.S. Consumer Product Safety Commission who has declared artificial turf fields pose little to no risks for its users, the same basic findings of a cooperative study by two New York state agencies released last month.

Last year, the Rubber Manufacturers Association (RMA) released a review of 126 scientific documents on the health and environmental effects of shredded tires in playground surfacing. It concluded that scrap tires have no harmful effects when used in playgrounds. (27)

However, Jeff Ruch, executive director of PEER (Public Employees for Environmental Responsibility) said he had not seen the RMA study, but added he wasn’t surprised that an industry-funded study would be favorable to the material.

Based on these assurances on safety, many governmental agencies seem to encourage crumb rubber usage. They have given grants. In 2007, Stan Cave, chief of staff to Governor Ernie Fletcher, and Teresa J. Hill, secretary of the Environmental and Public Protection Cabinet (EPPC), announced recipients of crumb rubber grants totaling $1.2 million at the agency’s government recycling warehouse. (28)

Despite safety assurances and grants, doubts still linger.

Especially with officials in the nation’s two largest cities.  They are not waiting  for ongoing studies and debate about the safety of artificial turf fields that use crumbs of the recycled tire rubber as a base.

The New York City Department of Parks and Recreation and the Los Angeles Unified School District have decided that any new artificial fields they purchase must use a different material as its base, or infill layer. The moves will mean using costlier alternatives such as one that uses coated grains of sand.

“The health of our students is more important than any other issue,” says LAUSD board member Marlene Canter, whose district includes Helen Bernstein High School in Hollywood where a coated sand called FlexSand was used in an artificial turf field that opened last fall. “You should never equate economics with health. In no way should we be skimping on something like this that could affect our kids.” (29)

In spring 2008, New Jersey officials found elevated lead levels in some older artificial fields; a number were closed. In September, the California Attorney General’s Office sued three turf manufacturers because they “failed to provide clear and reasonable warnings” that their products contained lead, a violation of state law.

Geoffrey Croft, president NYC Park Advocates, favors natural turf fields, but he said he’s glad the city is moving away from crumb rubber.

“We’ve been fighting against crumb rubber for years,” he says. “We’ve wanted them to abandon it. Up until recently, they’ve refused. I hope they take crumb rubber out of all the fields.”

Okay. Authorities are now beginning to realize the dangers of crumb rubber to children, but that still leaves us the problem of used tires. They are not going to diminish, especially with more and more car usage as populations grow.

What is being done by the tire companies to safe guard the environment from the rubber tire?

Obviously, a reduction of rubber tires and harmful chemicals within them, would help.

It would appear, with this concept in mind, Michelin have found a solution.  In 2005, it developed a radical new concept called the ‘TWEEL’.

Michelin TWEEL is a single non-pneumatic solution instead of the traditional tire and wheel combination.

The traditional rubber tire and solid wheel duo is replaced by a tread bonded to a strong loop of composite material. The vehicle’s weight hangs from a series of polymer plastic spokes that connect this loop to the hub.

The flexible spokes are fused with a deformable wheel that absorbs shocks and rebounds with ease. Without the air needed in conventional tires, Michelin TWEEL still delivers pneumatic-like load-carrying capacity, ride comfort and resistance to road hazards.

The TWEEL is expected to ‘deliver a performance that exceeds that of inflated tires’.

In TIME Magazine, the TWEEL was selected as “One of the most amazing inventions of 2005.”

That was 4 years ago.  How is it developing?

In 2008, Michelin developed a new lunar wheel for the next generation of NASA moon rover vehicles. The structurally supported tire and wheel assembly, made of breakthrough composite materials, was jointly developed at Michelin’s European and North American research centers.

The innovation will help meet NASA’s mobility challenges for manned and un-manned moon missions planned for the coming decade.

In 2009, Michelin technology provided astronauts with a smooth ride up Pennsylvania Avenue for the 56th presidential inaugural parade on Tuesday, Jan. 20, 2009.

The question is, will it provide the general public a smooth ride up Pennsylvania Avenue in their own vehicles?

It puts Michelin in a bit of a predicament. If the TWEEL was made available mainstream, what happens to the rubber industry, of which Michelin has significant investment?

What happens to the other industries involved, such as the chemical industry and the steel industry?

There’s no question it would benefit the public, especially children, and the environment.

But will it upset the shareholders by inflicting short term financial loss upon them while new production methods are implemented?

Will the tire be introduced in the mainstream or is there too much money to be lost?

We’ll have to wait and see.

As Marlene Canter stated; “You should never equate economics with health” .

Some crumbs of comfort.

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Ann Margrain

Founder, ‘Heroin and Cornflakes’ blog.

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Tags: Cancer, children and rubber crumb, Michelin motorised wheel, Michelin TWEEL, Mitchelin motorised wheel, Mitchelin tweel, rubber crumb and cancer, rubber crumb in playgrounds, rubber tire fire, rubber tire workers and cancer, tires and cancer, tyres and cancer