Study shows how waste generated by smoking can affect health

A study by scientists at the US Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), published in the journal Environmental Science & Technology, has identified for the first time how toxins generated by smoke, present on surfaces, can present a potential health risk to long term.

They found that concentrations of toxic chemical compounds that remain in indoor environments where cigarettes were smoked can exceed California State risk guidelines, meaning that nonsmokers can be exposed to health risks by living in contaminated spaces.

Also called third-hand smoke, this type of secondhand smoke refers to residual nicotine and other hazardous chemicals that contaminate the indoor environment after smoking.

This could be in the smell of clothing, in a hotel room, or any environment where a smoker has passed.

It may just seem like a harmless smell, but it is also indicative of the presence of tobacco toxins.

secondhand smoke

It is thought that only smokers are at risk for health problems such as cancer and heart disease. But non-smokers are also affected, whether by living in environments and with smokers or contact with indoor surfaces where a smoker has been present.

According to the World Health Organization (WHO), tobacco smoke contains over 4,000 known chemicals, many of which are harmful, with at least 40 causing cancer.

Secondhand smoke is a mixture of the smoke from the lit end of a cigarette and the smoke exhaled by a smoker. When it contaminates the air, especially indoors, it is inhaled by everyone, exposing smokers and non-smokers to its harmful effects.

This can be the cause of lung cancer in non-smokers and increase the risk of coronary heart disease. Although most smokers are men, many women and children are affected by secondhand smoke.

WHO data show that worldwide, secondhand smoke causes about 600,000 premature deaths per year, the majority (64%) among women.

However, even those who do not inhale smoke, and are exposed to a surface contaminated by smoke as well, can also be at risk for these diseases.

Previously, scientists at Berkeley Lab discovered that aerosolized nicotine, released during smoking and vaping, adsorbs to indoor surfaces, where it can interact with a compound present in indoor air called nitrous acid (HONO) — a common component of air. internal — to form highly carcinogenic compounds called tobacco-specific nitrosamines (TSNAs).

Nicotine accumulated on household surfaces can continuously generate TSNAs, long after the smoke has spread through the environment.

Health risk from third-hand smoke

TSNAs enter the body through several pathways. The study estimated some doses for inhalation and dust ingestion using indoor concentrations with TSNAs.

The team focused on dermal exposures, which are more difficult to measure and for which there is much less information.

These dermal exposures can occur directly through skin contact with polluted air or a contaminated surface that harbors TSNAs – for example, while sleeping on smoky sheets.

But they can also occur via epidermal chemistry, when nicotine already installed in the skin reacts with environmental HONO to form TSNAs directly on the surface of the body.

Berkeley Lab chemist Hugo Destaillats and lead author of the study said in a statement that the team integrated “new information produced over the past decade with our most recent results to estimate the daily doses that people may be exposed to when living in houses contaminated with third-hand smoke”.

The researchers found that the presence of skin oils and sweat on the surfaces of the evaluated model led to a higher yield of TSNAs in the presence of nitrous acid compared to clean surfaces.

“Nicotine is released in large amounts during smoking and coats all indoor surfaces, including human skin,” said Xiaochen Tang, who led the Berkeley Lab’s experimental efforts at the Indoor Environment Group.

Three different TSNAs were formed in this reaction, two of which (named by the acronyms NNK and NNN) are known carcinogens. There is less toxicological information for the third, NNA, which is not present in tobacco smoke. For this reason, the study included an in vitro evaluation (tests carried out in laboratories with generally glass equipment).

The researchers then evaluated the toxicological effect of NNA in laboratory-grown lung cells. “Contact with NNA led to DNA damage, including double-strand breaks, the most deleterious genotoxic outcome,” said Bo Hang, co-author of the Biosciences Area at Berkeley Lab.

Effects of substances on the skin

To better understand skin exposures of the substances, a group of researchers from the University of California Riverside Consortium and UC San Francisco evaluated how the compound NNK and nicotine penetrate the skin of mice.

Co-author Manuela Martins-Green, from UC Riverside, pointed out that “under the experimental conditions used, analysis of the metabolites in rat urine showed that, for both compounds, direct dermal contact resulted in accumulation and circulation in the body for seven days after discontinuation of dermal exposure.”

Analysis has shown that exposure through all of these pathways – inhalation, dust ingestion and dermal absorption – under typical indoor conditions can result in doses of the NNK compound that exceed health guidelines known as “Non-Significant Risk Levels” set by the Office. of California Environmental Health Risk.

These cumulative exposures can contribute to an increased risk of cancer. Dermal exposure pathways significantly contribute to TSNA intake at levels that can be comparable or even superior to inhalation.

According to Neal Benowitz, a UCSF professor and co-author of the study, “These findings illustrate the potential health impacts of third-hand smoke, which contains not just TSNAs but hundreds of other chemicals, some of which are also known to be carcinogens. ”.

As a next step, the researchers said they will explore in more detail the mechanisms of “adverse health effects associated with tobacco and cannabis residues, effective remediation strategies, and translation of scientific findings into tobacco control practice.”