Did a girl get leukemia from sleeping on a brown mattress? An article to understand why oncologists disagree with this conclusion

Real points:

1. Formaldehyde is indeed an environmental factor that can cause leukemia, but whether or not a person exposed to it will develop cancer also depends on the level of exposure, including exposure concentration and exposure duration.

2. Factory workers who produce formaldehyde-related products have a higher risk of leukemia due to occupational exposure, but there is currently no clear evidence to support that formaldehyde residues in brown mattresses can directly cause leukemia.

Verifier: Hippocrates' disciple | Oncologist

Recently, a video about a 6-year-old girl contracting leukemia after sleeping on a straw mat pressed with glue has attracted attention. However, a careful search did not reveal a clear source of the news. Most of the accounts that spread the video were short video marketing accounts labeled "furniture," "decoration," "environmental protection technology company," etc., and their authenticity is questionable.

However, similar news has actually happened. In 2012, a 5-year-old girl in Guangdong was diagnosed with acute leukemia after she went to the doctor because of persistent coughing. Her parents checked the coir mattress that the girl had slept on for "half a year", and the formaldehyde test results showed that "the formaldehyde concentration in the air was 0.329mg/m3, which greatly exceeded the Class I standard limit." The parents took the coir mattress manufacturer to court, and the first-instance court finally determined that the mattress did contain excessive formaldehyde and ordered the mattress manufacturer to bear 40% of the compensation, totaling 169,000 yuan.

The various versions of the story that "a girl slept on a coir mattress and developed leukemia" that circulated online should all have evolved from this case. Combining this old news, we can analyze the relationship between excessive formaldehyde in coir mattresses and childhood leukemia.

1. The formaldehyde content of the girl's mattress in the case 8 years ago was indeed excessive

There are two sets of national standards for limiting formaldehyde content in residential buildings in my country:

1. GB50325-2020 "Standard for Indoor Environmental Pollution Control of Civil Construction Projects"

The new version of the "Standard for Indoor Environmental Pollution Control of Civil Construction Projects" was officially implemented on August 1, 2020. It was jointly issued by the Ministry of Housing and Urban-Rural Development and the State Administration for Market Regulation. The standard stipulates that the formaldehyde content of Class 1 civil construction projects must be less than 0.07 mg/m3. This regulation is mandatory and stricter than previous standards. The "Code for Indoor Environmental Pollution Control of Civil Construction Projects" (GB50325-2010) implemented before this stipulated that the formaldehyde content should be less than 0.08 mg/m3

2. GB/T18883-2002 "Indoor Air Quality Standard"

This standard was jointly issued by the former General Administration of Quality Supervision, Inspection and Quarantine, the Ministry of Health and the State Environmental Protection Administration. The indoor formaldehyde content requirement is less than 0.1 mg/m3, which is only advisory.

Regardless of the standard, as long as the testing agency is qualified and the testing method is in line with the label, the formaldehyde content of the brown mattress (0.329mg/m3) is above the standard.

2. Can formaldehyde cause leukemia?

Formaldehyde is indeed an environmental factor that can cause leukemia. The International Agency for Research on Cancer classifies formaldehyde as a Class 1 carcinogen, which means it is a proven carcinogen that may cause leukemia. However, whether or not you will get cancer also depends on the level of exposure. The exposure level includes two aspects: exposure concentration and exposure duration.

Currently, a large number of studies have shown that occupational exposure to formaldehyde is correlated with the incidence of leukemia, but research on formaldehyde in residential decoration and furniture (non-occupational exposure) is still lacking.

Formaldehyde is used in the production of resins, plastics, photographic films, decorative laminates and plywood, and as a fungicide and tissue preservative. Workers in factories that produce these products are at risk of occupational exposure to formaldehyde.

A 2003 paper from the National Cancer Institute of the United States showed that 25,619 workers who were in close contact with formaldehyde at work had a higher risk of dying from leukemia than the average person. The average formaldehyde content in the air in their workplace reached 1 ppm (equivalent to 1.28 mg/m3) or the peak reached 4 ppm (equivalent to 5.12 mg/m3), which significantly increased the risk of leukemia by 2.49 times and 3.46 times respectively. The study also showed that formaldehyde exposure below the above average or peak content did not significantly increase the risk of leukemia.

Another study in 2004 clarified the relationship between exposure time and leukemia, and believed that if the exposure time of formaldehyde is more than 10 years or the first exposure time is more than 20 years ago, the standard mortality rate will increase by nearly 2 times. This study showed that the minimum concentration of formaldehyde is 0.15ppm, which is equivalent to 0.2mg/m3.

3. Will the formaldehyde residue in brown mattresses cause leukemia?

There is no evidence to support this, and the current inclination is no.

As mentioned before, formaldehyde causes cancer mainly for occupational exposure of factory workers. These workplaces have sources that continuously produce and replenish formaldehyde, which can cause continuous formaldehyde pollution in the environment, and there is also long-term exposure. For the case of the girl in the case, although the formaldehyde in the brown mattress exceeds the standard, there is no continuous source of formaldehyde replenishment. The formaldehyde continues to decay during the volatilization process, and the concentration is getting lower and lower, so it is impossible to have high-concentration exposure. The exposure time of low concentration must be longer than 10 years before the risk of death will increase by nearly 2 times, but the mattress of the Guangdong girl was used for half a year, which obviously did not reach this length of time. Therefore, the girl's formaldehyde exposure level is completely not equivalent to the occupational formaldehyde exposure of factory workers.

A review published in an authoritative academic journal in 2010 found a total of two studies, neither of which showed a link between household formaldehyde and childhood leukemia. The review mentioned that childhood leukemia had no relationship with household pesticides or gasoline.

The American Cancer Society states that the exact cause of most childhood leukemias cannot be found, and that children with leukemia do not have any risk factors for cancer that are different from other children. The National Cancer Institute states that only 5% of childhood cancers are genetically related, and that some known environmental carcinogens (such as gasoline, pesticides, infections, nuclear power plants, etc.) have mixed effects on children, and there is insufficient evidence to prove that these environmental carcinogens are causally related to childhood leukemia.

But we actually see some children suffering from leukemia. Why is that?

When a person is seriously ill, especially a disease like cancer, they instinctively want to find the cause of the disease. When humans encounter misfortune, they have the urge to find causal relationships in order to seek a sense of comfort. This is an evolutionary survival instinct. Because if there is a definite causal relationship, we can actively avoid the cause and prevent the unfortunate results from happening again, which can help us increase the probability of survival in this uncertain world. However, good wishes and strong instincts, if not realized by scientific tools, may lead to rumors.

4. Why was the girl in this case able to obtain compensation from the manufacturer?

Scientific evidence is not the same as legal evidence. How scientists view scientific evidence is not the same as how judges view scientific evidence.

Take the example of the United States. Johnson & Johnson was ordered to pay a medical guide $417 million in compensation. The judge believed that the long-term use of talcum powder produced by Johnson & Johnson was related to the guide's ovarian cancer.

In fact, there is controversy in the scientific community over whether talcum powder causes ovarian cancer, and the evidence is very unclear. In theory, some formulas of talcum powder are natural minerals of magnesium and aluminum, which are often associated with asbestos. If talcum powder containing asbestos residues is frequently applied around the genitals, it may travel along the reproductive tract and retrograde to the ovaries, causing ovarian inflammation, and further inducing ovarian cancer.

However, the theoretical possibility is still far from the actual causal relationship. Some studies have shown that long-term use of talcum powder will slightly increase the risk of ovarian cancer, while other studies have shown that it does not increase the risk of ovarian cancer. The International Agency for Research on Cancer classifies the use of talcum powder around the genitals as a Class 2B carcinogen, which is much weaker than the evidence for formaldehyde.

In the girl's case, the Chinese judge also mentioned that the mattresses produced by the palm mattress manufacturer did have formaldehyde levels that seriously exceeded the standard. Due to the current scientific and medical limitations, the victim was unable to directly provide evidence to prove that there was a causal relationship between her leukemia and the use of a mattress with excessive formaldehyde emissions, but the causal relationship between the two could not be absolutely ruled out. Therefore, the manufacturer was finally sentenced to bear 40% of the compensation liability. This is the current mainstream legal concept of protecting consumer rights and reversing the burden of proof, which is similar to the Johnson & Johnson talcum powder incident in the United States.

Editor of this article: yhxi