Are you still using it to wipe your mouth? It is recommended to replace it immediately

A few days ago, I had just finished a meal and was using a toilet paper roll to wipe my mouth. When my classmate saw me, he kindly reminded me with a little embarrassment: "Toilet paper rolls are for going to the toilet, not for wiping your mouth. You should use tissue paper to wipe your mouth." I was shocked when I heard that, and I started to look up information with a skeptical attitude, wanting to see what the difference is between toilet paper rolls and tissue paper rolls, and also wanting to see if I really used them wrongly in the past few years?

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On the surface, toilet paper rolls and tissue paper are just different in the form of paper. However, as industrial products, toilet paper rolls and tissue paper are produced by enterprises in strict accordance with relevant standards, so if you want to understand their differences in depth, you need to check the production standards behind them .

The standard commonly used for toilet paper rolls on the market is GB/T 20810-2018 "Toilet Paper (including toilet paper base paper)" (hereinafter referred to as the "tissue paper roll standard"), while tissue paper is mostly based on GB/T 20808-2022 "Paper Towels" (hereinafter referred to as the "tissue paper standard").

You may not be familiar with the name of the standard, so here is a brief introduction:

The "GB" in the standard is the pinyin initials of "Guo Biao", which means "national standard";

“T” is the pinyin initials of “推”, which means “recommend”;

"20810" and "20808" are standard sequential numbers;

The last "2018" and "2022" are the release years of the standards, and the standards are generally updated from time to time.

You are not mistaken, these two standards are recommended national standards, not mandatory .

However, each country has its own laws and each industry has its own rules. For reasons of approval, sales, and other aspects, manufacturers generally follow these standards and will also indicate them on the final product. These standards are publicly released, and you can check them out if you are interested.

Standard instructions on toilet paper rolls (left) and tissue paper (right) Image source: Photographed by the author

1

Designed for different purposes

Perhaps it is a little surprising to everyone that the toilet paper standard actually clearly states in the first chapter that it applies to toilet paper, and also stipulates that the word "toilet paper" should be marked on the packaging of this paper , as shown in the figure below.

However, because the label is too small, many people may not have noticed it.

The "Toilet Use" instructions on toilet paper products. Image source: Photographed by the author

In contrast, the first chapter of the tissue paper standard states that the applicable objects are napkins and handkerchiefs, etc. , which is obviously more in line with the scene of my happy meal at the beginning.

It can also be seen from these statements that the original intention of designing toilet paper was for toilet use, and paper towels "wholeheartedly" play the role of napkins.

2

Papermaking raw materials have different requirements

When it comes to papermaking, I believe everyone is familiar with it. It is one of the four great inventions of my country and has had a profound impact on the progress of human civilization. During the Eastern Han Dynasty, Cai Lun improved the papermaking technique and made paper from raw materials such as tree bark, hemp heads and worn cloth. The paper was of good quality and low price, which greatly promoted the spread and use of paper.

In fact, to this day, the commonly used papermaking raw materials (paper pulp) are not much different from those of the ancients, and the classification is shown in the figure below. The fibers in the pulp are used to make strong and tough paper .

Pulp classification Image source: self-made by the author

It is generally believed that virgin wood pulp has the best quality, virgin non-wood pulp is the second best, and recycled pulp has the worst quality . The toilet paper standard allows the use of virgin pulp or recycled pulp. Virgin pulp toilet paper can be divided into superior, first-class and qualified products according to quality (superior products are the best, and qualified products are the worst); while the tissue paper standard requires that it must be virgin pulp, and ordinary types can be divided into superior and qualified products.

However, you don’t need to worry too much. In actual products, the raw materials of most brands of toilet paper are marked as "100% virgin wood pulp", and the quality should be guaranteed. In addition, some businesses have recently promoted pure wood pulp. Here we need to remind everyone that pure wood pulp is different from virgin wood pulp. Virgin wood pulp comes from natural wood, while pure wood pulp may include recycled second-hand wood pulp .

Commercial pulp and quality description of toilet paper and tissue paper Image source: Photographed by the author

3

Different microbial requirements

According to production standards, the total bacterial colony count of toilet paper should not exceed 600 CFU/g, while that of paper towels should not exceed 200 CFU/g . CFU stands for "colony-forming unit", and "600" and "200" can be understood as the number of colonies on a culture dish.

Some readers may wonder why "total bacterial colony count" sounds a bit strange. Why not use "bacterial count"? In fact, it's not that researchers don't want to use it. The main reason is that bacteria are too small and too many to be counted one by one with the naked eye, which makes it difficult for researchers.

Later, some people thought that when bacteria grow, they often develop into a colony with themselves as the center. Each colony means that there is at least one bacterium here at the beginning, so the number of colonies after a period of culture is used to represent the number of bacteria at the beginning.

Image of bacterial colonies on a culture dish: Reference [4]

If the density of paper is calculated as 0.5g/cm3, for a section of roll paper, assuming the length is 16cm, the width is 12cm, and the thickness is 0.025cm, the weight is 16×12×0.025×0.5=2.4g, and the total number of bacterial colonies does not exceed 1440CFU ; for a piece of tissue paper, assuming the length is 20cm, the width is 16cm, and the thickness is 0.025cm, the weight is 20×16×0.025×0.5=4g, and the total number of bacterial colonies does not exceed 800CFU .

Considering that the area of ​​a single roll of toilet paper is generally smaller than that of a single piece of toilet paper, and the amount of toilet paper used is often greater, the difference in the number of bacteria between the two will be greater in real life. Of course, the size and thickness of different papers vary, and this estimate is for reference only. The specific details are subject to testing.

Comparison of toilet paper and paper towel Image source: Photographed by the author

From the perspective of quantity, paper towels are indeed more hygienic, but how much more hygienic they are may not be clear to everyone. Let's take hands and mobile phones, which are very familiar to everyone, as an example. In 2015, Chengdu Third People's Hospital went into office buildings to carry out a public welfare project of bacteria detection on "Global Handwashing Day". The results showed that the total number of bacterial colonies on one hand of a working person before washing can reach 500 CFU .

The numbers may not be shocking enough. Here is a picture. It shows the results of American biologist Tasha Sturm's son who had just returned from playing outside putting his fingerprints on a culture dish. The picture is shocking.

However, it is worth mentioning that washing hands can effectively reduce the number of bacteria on your hands . In the activity mentioned above, Chengdu Third Hospital found that the total bacterial colony count of working people can be reduced to below 5 CFU after washing their hands.

Image of bacterial colonies cultured from handprints: Reference [6]

In August 2018, the British Daily Mail reported that mobile phone screens are the worst place for filth and dirt to hide . In the survey samples of mobile phone insurance company Insurance2go, the total number of bacterial colonies per square centimeter of the Samsung Galaxy 8 screen was 100 CFU, the iPhone 6 had 40 CFU, and the Google Pixel had 12 CFU. Let's take the iPhone 6 in the middle as an example to calculate. The iPhone 6 is 138.1mm high, 67.0mm wide, and has a front area of ​​92.527cm2.

Considering that it is not a full-screen design, the screen area is reduced to 80cm2, so the total number of CFU on the iPhone 6 screen is 40×80=3200, which does not include other areas such as the back of the phone. Here we recommend that you clean your phone regularly and put down your reluctant phone when dining . After all, a short separation is for a better reunion.

The mobile phone screen that we spend every day together. Image source: Tuchong Creative

In comparison, if both toilet paper and paper towels meet the standards, the difference in the number of bacteria between a toilet paper roll and a paper towel is roughly equivalent to the number of bacteria on one hand, or 1/5 of the number of bacteria on a mobile phone screen.

4

Different technical indicators

There are many differences in the technical indicators of roll paper and tissue paper, among which the more concerned ones are the migratable fluorescent substances, heavy metal content and longitudinal wet tensile strength .

"Migration" means that the substance can be transferred to the skin or mucous membranes through touch; "fluorescent substance" mainly refers to the fluorescent whitening agent used by manufacturers to make paper towels appear whiter. It is a complex organic compound that may cause harm after entering the body.

There is a stratum corneum on the surface of human skin, which can prevent the skin from absorbing large molecular organic substances such as fluorescent whitening agents. However, when we wipe our mouths with tissues, if there are migratable fluorescent whitening agents in the paper, it may enter the mouth and cause health risks .

The production standards clearly require that no migratable fluorescent substances be detected on the paper surface of tissue paper and toilet paper made of virgin pulp. However, no such requirements are made for toilet paper made of recycled pulp, posing a safety hazard.

In terms of heavy metal content, the types of elements tested for tissue paper are more numerous than those for toilet paper, and the standards are also stricter, as shown in the following table:

Perhaps because virgin pulp is relatively safer, the paper standards have not yet made clear requirements for the heavy metal content of virgin pulp paper. The paper requirements here are the requirements for recycled pulp paper. Image source: References 1, 2

Due to usage requirements, tissue paper requires a higher longitudinal wet tensile strength . It remains strong after coming into contact with water and does not get paper scraps everywhere, making it convenient for wiping the mouth, dining table, etc.; while roll paper requires a lower longitudinal wet tensile strength . After use in the toilet, it disperses quickly when it comes into contact with water to avoid clogging the sewer.

We can do a simple experiment to verify this. As shown in the figure, put a piece of toilet paper and a piece of tissue paper into the same cup of water. After stirring for the same time, the toilet paper is torn and scattered, and the water in the cup becomes turbid; while the tissue paper remains intact, and the water in the cup is relatively clear. If you are interested, you can try it yourself.

Stirring experiment results: rolling paper on the left, pulling paper on the right Image source: taken by the author

Back to the original question: Can toilet paper be used to wipe your mouth? In fact, through the previous analysis, we can see that the various indicators of toilet paper are designed for toilet use. If conditions permit, it is recommended to use special paper for special purposes , use tissue paper for napkins, and use toilet paper for toilet paper.

Of course, because most brands of toilet paper are of good quality, if you don't have any toilet paper with you, it's okay to use a good quality toilet paper as a napkin. Just like soap and soap, if the soap happens to be used up, you can occasionally use soap to wash your hands. However, if you encounter toilet paper of unknown quality provided by small restaurants or public toilets on the street, it is recommended to be careful and not use it to wipe your mouth.

Finally, we need to remind everyone that both toilet paper and paper towels have a shelf life, which is generally 3 years , and is also indicated on the packaging. After the shelf life, the number of microorganisms in the paper may have exceeded the applicable range, and the strength and toughness are no longer guaranteed. At this time, it is not recommended that you continue to use these papers, at least do not use them to wipe the skin (it can be used to clean tables and cabinets, etc.) to protect our health.

Author: Xiao Yidong (University of Chinese Academy of Sciences) Zhang Yi (Southeast University)

Note:

1. GB/T 20808-2022 "Paper Towels" is a standard that was just updated and released this year and will be implemented in May 2023;

2. Because GB/T 20810-2018 "Toilet Paper (including Toilet Paper Base)" and GB/T 20808-2022 "Paper Towels" are both recommended national standards, not mandatory standards, some big-name manufacturers may not follow these standards when producing some products, but instead follow their own corporate standards, which are usually named with the pinyin initials "Q" of "enterprise", such as Q/KHBW003, etc. However, don't worry, corporate standards must be reported to the competent authorities for filing and must not be lower than mandatory national standards.

3. You will often see a hygiene standard GB 15979-2002 "Hygiene Standard for Disposable Sanitary Products" on the packaging of tissue paper and handkerchief paper. This is a mandatory national standard applicable to a variety of disposable sanitary products (such as masks, disposable gloves, sanitary napkins, etc.).

References:

[1] GB/T 20810-2018, “Toilet paper (including toilet paper base paper)” [S]. Beijing: State Administration for Market Regulation, China National Standardization Administration, 2018.

[2] GB/T 20808-2022, Paper Towels[S]. Beijing: State Administration for Market Regulation, National Standardization Administration, 2022.

[3] Baidu Encyclopedia - Cai Lun.

[4] Microbiological testing unit of measurement: Comparison of the difference between CFU and MPN [EB/OL], https://www.huankai.com/show/35488.html, 2021-08-31.

[5] Wang Liao. Global Handwashing Day: Chengdu Three Hospitals Experiment: One Hand Carries 500 Bacteria [EB/OL], https://sichuan.scol.com.cn/fffy/201510/54024295.html, 2015-10-15.

[6]Margarita Noriega. Here's how to make your own bacteria handprint[EB/OL], https://www.vox.com/2015/6/8/8744399/bacteria-handprint, 2015-06-08.

[7] Fu Shuyi. Foreign media survey finds that the bacteria on smartphones are ten times that of toilet seats [EB/OL], http://it.people.com.cn/n1/2018/0825/c1009-30250943.html, 2018-08-25.

[8] iPhone 6 - Technical Specifications [EB/OL], https://support.apple.com/kb/sp705?locale=zh_CN, 2021-4-15.

[9] Wood pulp paper and bamboo pulp paper, one word difference makes a big difference! Are you using toilet paper correctly? [EB/OL], http://www.hbzjy.com/content/?2283.html, 2018-01-18.

[10] GB 15979-2002, Hygiene Standard for Disposable Sanitary Products [S]. Beijing: General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China, 2002.

This article is produced by Science Popularization China and supervised by China Science Popularization Expo

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