The plastic in the filter itself is non-biodegradable waste that can be consumed by wildlife, pets, and humans.
Cigarette butts are the single most littered item in the entire world - but they often go unnoticed. Trillions are dumped into the environment each year and they now have been found to be toxic, hazardous waste.
Thomas Novotny, professor of global health at the University of California in San Diego and a founding member of Cigarette Butt Pollution Project, argues that they should be regulated by environmental law.
Novotny told The Ecologist: "I am a family physician who first saw the end results of smoking among my patients. I became a public health specialist so that I could better address the preventive aspects of tobacco use.
"I am also a passionate environmentalist who saw that the environmental community could become a stronger ally and better reduce the health and environmental impacts of tobacco use."
Although the annual global cleanups show that cigarette butts are everywhere, there is no positive movement towards a solution. For Novotny and his colleagues "it seemed important to organise efforts to address this environmental blight while trying to reduce the health effects of smoking too".
Both smokers and nonsmokers mostly think that filters are made of biodegradable material and that they reduce harm. But they make it easier - not healthier - to smoke. They are a marketing ploy.
Novotny goes so far as to argue that filters encourage deeper inhalation of toxic smoke.
Filters are not harmless pieces of biodegradable material but a combination of a plastic and toxic tobacco remnants. We still don’t know enough about the hazards the butts introduce into our environments.
The plastic in the filter itself is non-biodegradable waste that can be consumed by wildlife, pets, and humans. Ultraviolet rays from the sun will eventually break them into smaller microplastics that will find their way into the food chain and human bodies.
As for the chemicals, so far it has been shown that nicotine, ethylphenol, and heavy metals are leached from butts.
Novotny explained: "We are examining the leachates now to see if the chemicals can bioaccumulate and potentially enter the food chain. It is difficult to predict how much of threat the butts are to oceans and marine life.
"We are now trying to identify environmental markers for that waste so that we can understand the risk presented. We know that wildlife have consumed butts and that they move from storm drains to streams to rivers and onto beaches. Here, they are a blight that spoils the environment and become a public nuisance".
The Cigarette Butt Pollution Project is lobbying for a legislative solution to this kind of waste.
Novotny said: "We could ban the sale of filtered cigarettes; impose a litter fee on packages of cigarettes sold; add a label on cigarettes identifying the butt as a hazardous waste product; create take-back programs that are funded by the tobacco industry to collect and dispose of butt waste at their expense; educate the public about the environmental impacts of butt waste; and try hard to get people to quit smoking".
But this campaigning is a slow process. So far in California, legislation to ban the sale of single-use filtered cigarettes has been proposed three times. Each time there has been increased support for this effort - but the ban is still not implemented.
The biggest improvement has been made in San Francisco where they charge 60 cents for each packet of cigarettes, amounting to millions of dollars. This money is then used to clean the butts from the environment.
Novotny concluded: "With new scientific information and advocacy partners, I anticipate that such legislation will succeed. For now, we will focus on local legislation to ban filtered cigarettes.
"There have been models for similar kinds of legislation in the US and elsewhere. For an example - in fighting for bans on flavoured tobacco products by municipalities - campaigners have argued that filters make it easier to establish nicotine addiction. The same argument may be used again."
Marina Kelava is an environmental journalist based in Zagreb, Croatia.