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Underwater Naturalist Article

"Underwater Naturalist"
Bulletin of the
American Littoral Society
Volume 25, Number 2
August 2000


Cigarette butts are the most common form of plastic
litter on the beaches of the U.S. and world-wide.
Toxic chemicals can leach out of the butts.
Photo by Chris Register
Cigarette Butts as Litter - Toxic as Well as Ugly?

By KATHLEEN REGISTER

Kathleen Register is the founder and executive director of Clean Virginia Waterways, and coordinates the International Coastal Cleanup in Virginia. She is adjunct faculty in the Department of Natural Sciences at Longwood College in Farmville, V A. She and her husband love to tag and release bluefish.

Every beach-goer has seen them -- cigarette butts littering the shore. Beyond being unsightly, does cigarette litter present a threat to organisms? This article summarizes research conducted to determine if the compounds in discarded cigarette butts (the filters and remnant tobacco) are biohazards to the water flea (Daphnia magna). Short-term bioassays (48 hours) using the water flea as the test organism were conducted. The results indicate that the chemicals released into freshwater environments from cigarette butts are lethal to Daphnia at concentrations of 0.125 cigarette butts per liter (one butt per two gallons of water).

Smokers discard billions of cigarette butts yearly, tossing many directly into the environment. Cigarette butts accumulate outside of buildings, on parking lots and streets where they can be transported through storm drains to streams, rivers, and beaches.

Some background on cigarettes

95% of cigarette filters are made of cellulose acetate, a plastic slow to degrade. Cellulose acetate fibers are thinner than sewing thread, white, and packed tightly together to create a filter; they can look like cotton. Cigarette filters are specifically designed to absorb vapors and to accumulate particulate smoke components. Cultivated tobacco, Nicotiana tabacum, is a member of the nightshade family of plants. It is a broadleaf native of tropical America cultivated as an annual.

Depending on the type of tobacco and its growing location, the leaves of the tobacco plant can have different tastes, burning properties, aromas, color, and nicotine content. Tobacco leaves contain several alkaloids, including the highly toxic alkaloid nicotine. Nicotine is a powerful insecticide and among the deadliest of all plant products in its pure form. According to the U.S. Department of Health and Human Services, it raises blood pressure, affects the central nervous system, and constricts blood vessels in humans. Nicotine is a colorless liquid highly soluble in water, and readily absorbed through the skin in its pure form. Potentially hundreds of additives are mixed with tobacco during the manufacturing process. Additives to smoking tobacco include flavorings and humectants used to keep tobacco moist. According to a publication written for the tobacco industry, additives can constitute ten percent of the weight of the "tobacco" portion of a cigarette, and four percent of the entire cigarette. A widely used cigarette additive is menthol, which provides flavor and serves as an anesthetic. When burned, many additives form new compounds, possessing unique properties. The "tar" often referred to in connection with cigarettes is not a black petroleum tar product, but instead refers to the hundreds of substances and additives found in tobacco. Tar, when cool, is a sticky yellow-brown substance and the U.S. Department of Health and Human Services states that it is composed of organic and inorganic chemicals, including some carcinogens. The complete list of 1,400 potential tobacco additives, which include sweeteners and flavors such as cocoa, rum, licorice, sugar, and fruit juices is considered a trade secret. Since tobacco is not classified as a food or drug, there are no legal maximums on agricultural chemicals or chemical additives cigarettes may contain.

The transparent crustacean Daphnia (often called a water flea) are planktonic animals which occupy a critical position in aquatic ecosystems, as they transfer energy and organic matter from algae to higher consumers. Tests using Daphnia have been widely used for decades to estimate acute toxicity. Illustration by Chris Register © DO NOT COPY OR REPRODUCE WITHOUT PERMISSION!

Emergence of the issue

Cigarette butts accumulate in the environment due to the popularity of plastic cigarette filters and the habit some smokers have to "toss their butt" rather than use ashtrays. Prior to 1954, most cigarettes were non-filtered. In the mid-1950s, sales of filtered cigarettes increased dramatically as the cause-effect relationship between smoking and cancer was reported extensively in the press. Before these reports, in 1950, sales of filtered cigarettes in the U.S. were 1.5% of all cigarette sales. Now, more than 97% of cigarettes sold in the U .S. have filters.

The recent bans on indoor smoking have also appeared to cause a shift in cigarette butt deposition. Circumstantial evidence indicates that more cigarette butts are accumulating outside of buildings due to the popularity of indoor smoking bans. In Australia, cigarette butts account for 50% of all litter, a trend that the executive director of Keep Australia Clean blames partly on indoor no-smoking policies.

How many discarded cigarette butts are there? Trillions. Global tobacco consumption has more than doubled in the last 30 years, and world cigarette production reached a record high in 1997 according to the U.S. Department of Agriculture (USDA).

The USDA estimated that in 1998, 470 billion cigarettes were consumed in the U.S.; world cigarette production was 5.608 trillion. The World Health Organization estimates that 1.1 billion people in the world smoke -- that is one third of all people on earth over the age of 15.

The 470 billion cigarettes smoked in the United States in 1998 translates to a total of 176,250,000 pounds of discarded butts in one year in the United States alone. The filters from 5.608 trillion cigarettes (approximate world production) would weigh more than 2.1 billion pounds (Table 1). This figure does not include the weight of the tobacco still attached to the filter, or the packaging, matches, disposable lighters, and other "collateral" waste that is generated by smoking.

The filters on one pack of 20 cigarettes weigh 0.12 ounces (with no tobacco attached) and displaces a volume of 10 ml. With annual world-wide production of cigarettes at 5.608 trillion, the potential weight and volume of cigarette butts becomes enormous (Table 1).

Similarly, cigarette butts take up a large volume of space. If one person smokes a pack and a half a day, he will consume more than 10,000 cigarettes in a year. This number of cigarette butts (filters only --not including remnant tobacco) will fill a volume of five liters. Worldwide annual consumption of cigarettes creates enough cigarette butt waste to fill more than 2,800,000,000 liters (2,800,000 m3).

Table 1 -- Weight and Volume of Discarded Cigarette Filters*

Number of filters

ounces/pounds

milliliters/liters

20

(one pack)

.12 oz

10ml

10,000

(one year's consumption for one smoker)

3.75 lbs

51iters

1,000,000

375 lbs

500 liters

100,000,000

37,500 lbs

50,000 liters

10,000,000,000

3,750,000 lbs

5,000,000 liters

100,000,000,000

37,500,000 lbs

50,000,000 liters

470,000,000,000

(Number of cigarettes smoked in the U.S. in 1998)

176,250,000 lbs

235,000,000 liters

1,000,000,000,000

375,000,000 lbs

500,000,000 liters

5,608,000,000,000

(1998 world cigarette production)

2,103,000,000 lbs

2,804,000,000 liters

*The percentage of cigarettes with filters varies, depending on the country.

There is one measure as to how many cigarette butts are finding their way into streams, rivers, and coastal environments. The International Coastal Cleanup Day, organized annually by the Center for Marine Conservation, involves more than 500,000 volunteers picking up debris from beaches, rivers, and streams around the world. Volunteers complete Marine Debris Data Cards indicating the quantity and type of litter they pick up. Cigarette butts were the most common debris item collected during the international cleanup, numbering 1,616,841 in 1998. Cigarette butts have topped the list in all CMC International Coastal Cleanups since they were added to the Data Cards as a separate item in 1990.

Because of the vast inflow of cigarette butts into the environment, experiments were conducted to determine if cigarette butts as litter present an environmental problem beyond aesthetics and have a measurable toxic effect when they enter the aquatic environment.

A series of bioassays (tests which use the response of a living organism to determine the effective level of a chemical in the environment) were conducted. One of the organisms most studied in aquatic bioassays is the planktonic animal Daphnia magna, often called a water flea. Static acute toxicity tests using D. magna have been widely used for decades to estimate the acute toxicity of chemicals to aquatic invertebrates. In aquatic ecosystems, water fleas occupy a critical position as they transfer energy and organic matter from primary producers (algae) to higher consumers such as fishes. Water fleas are small transparent crustaceans, have one central black compound eye, and swim in jerky motions. They feed by rhythmically beating their legs, collecting algae or bacteria on the filter-like bristles on their thoracic legs, and passing the food toward their mouths.

The Experiments

The large number of chemicals in used cigarette filters precluded toxicity testing of each chemical. Thus, a test that can estimate aquatic toxicity from the composite of chemicals and compounds found in cigarette butts was used.

Using the U.S. Environmental Protection Agency's 1996 "Aquatic invertebrate acute toxicity test for freshwater daphnids" standardized toxicology protocols and procedures, water fleas were introduced to petri dishes filled with dilution water and the test solution. For these experiments, the test solution was made by soaking the components of cigarette butts (remnant tobacco or the cellulose-acetate filters) in distilled, deionized water, and allowing the chemicals in the butts to leach into the water. Water fleas in the petri dishes were observed at 24 and 48 hours. In addition to death, any abnormal behavior or appearance was also recorded.

Data collected during the experiments were used to develop dose-response curves. Data were also used to determine the experimentally derived toxicant concentration producing death to 50% of the test population during continuous exposure over a specified period of time. This is referred to as the ”Lethal Concentrations 50" values (LC50). LC0 means no animals died, and LC100 means they all died. Lethal Concentrations provide a quantifiable measure and precise expression of toxicity.

Each test included controls consisting of the same conditions, procedures, and daphnids from the same population. The only difference being that none of the test chemical was added.

Prior to conducting the definitive experiments, three range-finding tests (preliminary hazard assessments) were conducted to establish parameters for the acute toxicity tests. The range-finding tests established test solution concentrations and leaching periods. The definitive tests had four components:

Experiment A - Used filters. To establish if the chemicals in used cigarette filters produce death in Daphnia after exposure to a specific concentration for a specified period of time. Remnant tobacco was removed from cigarette butts for this test. Filters from two cigarette butts were soaked in 500 ml of distilled, deionized water for one hour at room temperature. Twenty daphnids were exposed to each concentration level: 4, 2, 1, 0.5, 0.25, 0.125 butts per liter.

Experiment B - Remnant tobacco. To establish if the chemicals in the tobacco found in smoked, discarded cigarette butts produce death in Daphnia after exposure to a specific concentration for a specified period of time. Remnant tobacco (totaling 28 mm) from two cigarette butts was soaked in 500 ml of water for one hour at room temperature. Twenty daphnids were exposed to each concentration level: 4, 2, 1, 0.5, 0.25, 0.125 butts per liter.

Experiment C - New, unused filters. To establish if the chemicals in new, unused cigarette filters produce death in Daphnia after exposure to a specific concentration for a specified period of time. No tobacco was used in Experiment C. Daphnia were exposed to the chemicals that were leached out of new, unused filters to determine if any of the compounds in new filters were toxic to Daphnia. New filters were soaked in distilled, deionized water for one hour at room temperature. Twenty daphnids were exposed to each concentration level: 16, 8, 4, 2, 1, and 0.5 filters per liter.

Experiment D - Cigarette butts' effects on the pH of freshwater. To determine if the presence of cigarette butts in freshwater changes the pH of the water. pH is an important factor to aquatic animals, and can affect the toxicity of pollutants. For this experiment, one cigarette butt (the filter plus 28 mm of remnant tobacco) was soaked for one hour in 100 ml of spring water at room temperature. The pH of the water was measured before and after the one-hour soak using a Hach brand pH tester that had been calibrated just prior to the test.

Cigarette filters may look like cotton, but are made of cellulose acetate, a plastic that is slow to degrade in the environment. Cigarette filters are specifically designed to accumulate particulate smoke components including toxic chemicals. Photo by Chris Register.

Results

Experiment A (filter only). In this "filter only" experiment, 100% of the animals died after 48 hours in the concentrations that were equivalent to the chemicals found in two or more used cigarette filters per liter. In the 25% dilution, equivalent to one cigarette filter per liter of water, 20% of the Daphnia died within 48 hours. The LC50 was, therefore, between one and two used cigarette filters per liter. In concentrations of one used filter per liter and greater, deposits of material were noted on the swimming hairs of some Daphnia.

Experiment B (remnant tobacco only). In this "tobacco only" experiment, 100% of the animals died after 48 hours in the concentrations that were equivalent to the remnant tobacco from 0.5 or more cigarette butts per liter. In the solution that represented the remnant tobacco from 0.25 cigarette butts per liter, 80% of the animals were dead after 48 hours. In the most dilute solution, representing 0.125 remnant tobacco cigarette butts per liter, 15% of the Daphnia died in the testing period. The LC50 was, therefore, between 0.25 and 0.125 remnant tobacco cigarette butts per liter.

Comparing Experiments A & B. In both experiments, the swimming patterns of affected Daphnia resulted in a departure from the normal hop-sink swimming pattern. Before dying, some affected individuals whirled in one place, while others lay on the bottom, ineffectually beating their swimming hairs, but unable to produce net movement.

In the high and mid-range concentrations (0.25 to 4 cigarette butts per liter) of the tobacco-only group, Daphnia developed dark deposits or accumulations on their swimming hairs (setae) at 24 hours. Some Daphnia with this dark substance on their swimming hairs floated without attempting to swim, and several frequently became stuck together in groups. Deposits also formed on the animals in the filter-only group. These deposits were lighter colored and occurred only in the test solutions that were two or more filters per liter.

As seen in Figure 1, significant differences in acute toxicity among treatments were evident after 48 hours of exposure. The survival rates of the water flea were poorest in the tobacco-only test solutions. Acute toxicity at 48 hours was higher in the higher concentrations for both remnant tobacco and the cigarette filters. This indicates that the tobacco has a greater toxicity than the filters. For both tobacco and filters, the toxicity increased dramatically over a small interval. Such a steep slope of the dose-mortality curve indicates that individuals within a species will behave very similarly to each other in their response to the chemical (whereas a shallow slope of the curve indicates considerable variation in susceptibility to that particular chemical within a species).

1-- Tobacco only I 1-- Filter only I

Figure 1 Dose-mortality curve at 48 hours for the filter only and tobacco only doses.

Experiment C (new filters). The survival rates of the water fleas after 48 hours of emersion were poorest in the solutions with the higher concentrations of filters. But even at the highest concentrations of 16 new cigarette filters per liter of water, death rates were less than 50 percent.

Findings in control animals. At the conclusion of Experiments A, B and C, all water fleas in the control groups were alive, maintained a vigorous swimming pattern, and did not whirl or accumulate a dark substance on their swimming hairs.

Experiment D (effects of cigarette butts on pH). The pH of the tested water was 6.6 before cigarette butts were added, and remained 6.6 after cigarette butts soaked in the water for one hour. The presence of cigarette butts did not change the pH of the water.

Results of experiments

Given that exact real-world exposure of water fleas to cigarette butts is unknown, the tests done in this study cannot attempt to imitate the actual exposure. It is possible that the concentrations used in this study exaggerate the duration and dosage of exposure. It is recognized that exaggerating exposure can result in distortion, but it is felt by the author that the results of the experiments reveal relevant patterns.

Experiments A and B show that the chemicals in cigarette butts are acutely toxic to water fleas at concentrations higher than 0.125 cigarette butts per liter of water. This translates to one cigarette butt per 8 liters, or approximately one butt per two gallons of water. In addition, the evidence was strong that the remnant tobacco in cigarette butts is a principal factor determining the mortality, although the compounds in used cigarette filters also have a lethal effect on the water flea. The presence of the remnant tobacco from just one-half a cigarette butt per liter was enough to kill 100% of the animals, while it took the filters from two cigarette butts per liter to have the same 100% fatal outcome. The dark deposits that formed on the swimming hairs and affected the swimming patterns of the water flea suggest that this should be studied to determine if these deposits constitute a physical, rather than toxic, effect from this source of pollution.

The results of Experiment C indicate that the components of new cigarette filters are toxic only at concentrations very much higher than used filters. Even at a concentration of 16 new filters per liter (the equivalent of 64 new filters per gallon), the chemicals that leached from the filters killed less than 50% of the water flea. While the components of new cigarette filters may contribute to the total toxicity of cigarette butts, the chemicals and compounds that are absorbed by the filters during the act of smoking are responsible for most of the deaths associated with cigarette butts' filters.

The results of Experiment D show that the presence of cigarette butts in freshwater does not affect the pH of the water. This indicates that the chemicals leached from cigarette butts do not kill water fleas simply due to a change in the pH of the water.

Conclusions

Cigarette butts are the most common type of litter on earth. Collected, they weigh in the millions of pounds. The toxic chemicals absorbed by cigarettes' cellulose acetate filters and found in butts' remnant tobacco, are quickly leached from the butts by water.

The evidence indicates that the toxic chemicals leached from discarded cigarette butts present a biohazard to the water flea at concentrations of more than 0.125 butts per liter, or about one butt per two gallons of water. The leachate from the remnant tobacco portion of a cigarette butt is deadlier at smaller concentrations than are the chemicals that leach out of the filter portion of a butt.

Implications of research

The experiments summarized in this article are just the preliminary steps to fully understanding the impact cigarette litter has on our aquatic environment.

With cigarette butts identified as a biohazard, governmental agencies, environmental organizations, and anti-litter groups could educate smokers that littering cigarette butts causes harm to the environment.

Cigarette butts in the environment is a litter issue -- not a smoking issue. Just as the manufacturers of sodas have no control over the consumer's disposal of empty cans or bottles, cigarette manufacturers cannot control a smoker's behavior when it comes to the disposal of cigarette butts. Just as beverage manufacturers contribute to anti-litter campaigns, and have invested in public education on litter issues, so too should the tobacco industry. Thus far, cigarette manufacturers have made small efforts at anti-litter education. They need to take an active and responsible role in educating smokers about this issue and devote resources to the cleanup of cigarette litter. Strategies can include anti-litter messages on all packaging and advertisements, distribution of small, free portable ashtrays, and placement and maintenance of outdoor ashtrays in areas where smokers gather. Maybe cigarette packages can be redesigned to accommodate discarded butts.

In some states, consumers pay a small "anti-litter tax" every time they purchase a canned or bottled beverage. These funds support anti-litter efforts. A similar tax on cigarette purchases would go a long way toward funding campaigns aimed at eliminating the littering of butts. Picking up littered cigarette butts costs schools, businesses, and park agencies money. By taxing smokers for anti-litter educational efforts, some of the costs of cleaning up cigarette butts will shift onto smokers.

Smokers who now treat outdoor spaces as public ashtrays may reconsider their behavior when they learn that cigarette butts are made of plastic, not of cotton and paper; and worse, that cigarette butts contain chemicals that can kill some of the animals that occupy critical positions in aquatic communities. It is important that smokers' littering behavior be modified to decrease this source of pollution.

To help fund research on this topic or to contact the author, Kathleen Register, please send an e-mail to cleanva@longwood.lwc.edu.


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