Collective Masks Anti-Epidemic Capability (集體口罩抗疫力)

There are three effective in infection controls that employed in Hong Kong. They are frequency handwashing, social distancing (at least 1.5m) and wearing disposable surgery face mask. I try to propose a new term named Collective Masks Anti-Epidemic Capability (集體口罩抗疫力) to explain the positive control results from Asia people’s wearing mask practice through my following studies.

Introduction

In early March 2020, UK proposed “Herd Immunity” that once enough people get Covid-19, it will stop spreading on its own.  However, they haven’t considered the cost that will be devastating! (Ref. 1) The follow picture showed how herd immunity can stop a virus but it has an estimated fatality rate per infection somewhere around 1% (some region and special situation in hospital is much higher).

It verified not working now based on the trend of Covid-19 inflected in the world (Upto 2^nd Apr 2020). The only way to achieve herd immunity is through Covid-19 vaccine!

The nature of size distribution of viral aerosol and mask filtration effectiveness:

Why most Western people and experts think wear surgery face masks (not N95) are not effectively to protect people?  For example, US CDC recommends that healthy persons should not wear masks at all, only the sick ones.  Even though surgical masks, and improperly worn N95 respirator masks, do not offer perfect protection, the fact that wearing masks in Asian countries obtains a good result for controlling the inflection.

William G. Lindsley, etal. (2012) studied size distribution of cough-generated aerosol particles.  The average number of particles expelled per cough varied widely from patient to patient, ranging from 900 to 302,200 particles/cough while subjects had influenza and 1100 to 308,600 particles/cough after recovery.  When the subjects had influenza, an average of 63% of each subject's cough aerosol particle volume in the detection range was in the respirable size fraction (SD 22%), indicating that these particles could reach the alveolar region of the lungs if inhaled by another person. Most bio-aerosol size is below 1μm. (Ref. 2)

The below image shows the size of the coronavirus, relative to other small molecules like a red blood cell, or the often talked about PM2.5 particle size.

The follow table showed the different filtration effectiveness of different mask type. Most surgery face masks brought in market by citizen are ASTM F2100 Level 1 that BFE & PFE exceeds 95% or EN 14683 Type I that BFE exceeds 95%.

1.      BFE (bacterial filtration efficiency) measures how well the mask filters out bacteria when challenged with a bacteria-containing aerosol. ASTM specifies testing with a droplet size of 3.0 microns containing Staph. aureus (average size 0.6-0.8 microns). In order to be called a medical/surgical mask, a minimum 95% filtration rate is required. Moderate and high protection masks have bacterial filtration rates of 98% to greater than 99%.

2.      PFE (particulate filtration efficiency) measures how well a mask filters sub-micron particles with the expectation that viruses will be filtered in a similar manner. The higher the percentage, the better the mask efficiency. Although testing is available using a particle size from 0.1 to 5.0 microns, ASTM F2100-07 specifies that a particle size of 0.1 micron be used. When comparing test results it is important to note the size of the test particles used, as use of a larger particle size will produce a misleading PFE rating.

Recently, Sui Huang wrote an article named “COVID-19: Why we should all wear masks – There is new scientific rationale” on 27 Mar 2020. He said that small aerosols are carried by ventilation or by winds and thus can travel across rooms. The latest biological findings on SARS-Cov-2 viral entry into human tissue and sneeze/cough-droplet ballistics suggest that the major transmission mechanism is not via the fine aerosols but large droplets, and thus, warrant the wearing of surgical masks by everyone. (Ref. 3)

Only droplets below 10 micrometer diameter can reach the alveolae. The large spray droplets get stuck in the nose and throat (the naso-pharyngeal space) and in the upper air ducts of the lung, trachea and large bronchia.

Even with respect to the small aerosols we must not forget that the partial filtering provided by surgical masks is better than nothing.  The the particles leaked through mask and into environment was showed in the following diagram.  

On 31 Mar 2020, Ka Hung Chan and Kwok-Yung Yuen published an article in International Journal of Epidemiology (Ref. 4). They discussed three key epidemiological questions as follows:

Question 1: Can infected individuals reduce the risk of spreading the virus to others by wearing facemasks?

The answer to this is unambiguous.

Question 2: Can uninfected people reduce the risk of infection by wearing facemasks?

This is at the centre of the controversy.

Question 3: Can widespread use of facemasks in a population can facilitate the control of an epidemic?

The indirect impact of widespread use of facemasks must not be overlooked. It might increase the public’s risk awareness and improve their personal hygiene behaviours, many of which have been proven to be effective in infection control (e.g. handwashing, social distancing). The widespread use of facemasks may also reduce other droplet-transmitted infectious diseases, thus alleviating some burden on a highly-stressed health care system during an epidemic.

Preliminary Conclusion:

After study those paper and articles, I make a preliminary conclusion that the more people in a given population are wearing surgery face mask, the lesser probability for an individual to contact with that infectious agent through breaking.  It is because the inflection transmission link was broken or weaken both from suspended people breathing out and health people breathing in.  The following diagram is modified by herd immunity based on basic reproduction number (R0) equal to 4 and then reduce to R_n = 1 (Ref. 5).

I believe most of citizen wear surgery face mask could reduce the viral aerosol suspended in public area and indoor area so as to reduce the probability of Covid-19 inflection.  Therefore, I proposed a new term named “Collective Masks Anti-Epidemic Capability (CMAEC)” (集體口罩抗疫力) to describe Hong Kong, mainland China and Asia people practice of wearing face mask.  The further study on the model of CMAEC is valuable and verified by Asia practical successful cases. 

Some Additional Information:

My previous studies information about aerosol. (Ref. 6)

The curve A is experimental deposition velocities of aerosol showed the average is ~5x10^-2cm/s.

If man is 170cm height and his generated aerosol through cough will be deposited to ground after {(170/0.05)/60}min ~ 57min ~ 1hr! (Turbulence effect has not considered.)

Another study I performed was for indoor viable aerosol and its size distribution. (Ref. 7)

It was found that indoor airborne microbes most in the range of 1.1 to 2.1μm.  So that the mask of BFE could filter most of indoor airborne microbes >3μm; mask of BFE & PFE could filter all most all indoor airborne microbes (0.1 to 5μm)

Since aerosol suspends in the air as long as 1hr and indoor airborne microbes from the range of 1.1 to 7μm and above, wearing disposable face mask could help to remove at least bacteria level aerosol.

Reference:

1)      Antonio Regalado (2020) “What is herd immunity and can it stop the coronavirus?” MIT Technology Review - https://www.technologyreview.com/s/615375/what-is-herd-immunity-and-can-it-stop-the-coronavirus/

2)      William G. Lindsley, etal. (2012) Quantity and Size Distribution of Cough-Generated Aerosol Particles Produced by Influenza Patients During and After Illness”,  J Occup Environ Hyg. 2012; 9(7): 443–449. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4676262/pdf/nihms742694.pdf

3)      Sui Huang (2020) COVID-19: Why we should all wear masks – There is new scientific rationale - https://medium.com/@Cancerwarrior/covid-19-why-we-should-all-wear-masks-there-is-new-scientific-rationale-280e08ceee71

4)      Yuen, K.Y. & Chan, K.H. (2020). COVID-19 epidemic: disentangling the re-emerging controversy about medical facemasks from an epidemiological perspective. International Journal of Epidemiology, Published Online. dyaa044, https://doi.org/10.1093/ije/dyaa044

5)      Edward Nirenberg (2019) Herd Immunity: How Does It Work? https://medium.com/@edwardnirenberg/herd-immunity-how-does-it-work-28eeeeed2dfa

6)      Kim Hung, Lotto LAI (1997) “Detailed investigations on the inorganic chemical constituents of atmospheric aerosol and various deposition in Hong Kong” MPhil Thesis, City University of Hong Kong.

7)      Kim Hung Lotto LAI (2001) “A study of the characteristic of Indoor Air Quality in the multi-purpose premises” MSc Dissertation, Hong Kong Polytechnic University.

Modern Traditional Chinese Medicine (TCM) Clinic

Recently, I consult a Chinese Medicine Doctor in Science Park and find that The Nong's Chinese Medicine Clinic (農本方中醫診所) is a Modern Traditional Chinese Medicine (TCM) Clinic. They used a modern approach of concentrated Chinese Medicine granules, supported with a computerized program of their Management System.

From patient registration, diagnosis to prescription dispensation, all steps are computerized. The prescription dispensation is not using traditional form of herds but using concentrated individual Chinese Medicine granules. Each bottom of granules are identified by using bar code system first and then weighted a specific amount into a cup based on the electronic balance.

Then they put all different granules into a large bottom and mixing using the mixer. After that the mixed medicine granules are packed automatically.

All medicines dispensed are instantly soluble in hot water and require no decoction. The final product is shown as following photo.

It is totally different compared with Traditional Chinese Medicine Clinic which using original TCM herb. (e.g. The herd in the following book.)

High efficient, scientific and reduce time!

However, I am not sure that the effect between the mixed concentrated individual Chinese Medicine granules and extracted by mixed the original CM herbs are the same or not.

Reference:

The Nong's Chinese Medicine Clinic - http://www.nongs.com/clinics/index.htm

Easily Confused Chinese Medicines in Hong Kong (香港容易混淆中藥) - http://bublog.hkbu.edu.hk/bublog/html/blog.jsp?bid=17&pg=blogdetail&eid=173

HKJCICM > CM Database > Easily Confused Chinese Medicines in Hong Kong - http://www.hkjcicm.org/cm_database/confused/all_e.aspx?chapter=1

Yakult Light (More Health Care)

We visited Hong Kong Yakult Co. Ltd. on 7 November 2008. At that time, one of questions we asked was “How much sugar in each bottle?” The answer was about 14g. We asked why don’t Yakult to produce low sugar content product? They replied that they had already produced in Japan. Until now, we can buy “Yakult Light” and it claims ~40% less calories than regular Yakult.
(One gram of sugar, like that of any other carbohydrate, provides 4 calories in a person's daily diet.)

Moreover, one of company souvenirs was the book entitled “How the lactic acid bacteria in your daily diet may inhibit cancer?” I summarized part of the book into my blog named “Cancer Prevention and Intestinal Bacteria” (See reference).

My wife bought the Yakult Light with the Yakult Boy (Toys) during International Conference & Exhibition of the Modernization of Chinese Medicine & Health Products (國際現代化中醫藥及健康產品展覽會暨會議) (13 August 2010).

Reference:
Visit to Hong Kong Yakult Co. Ltd. - http://qualityalchemist.blogspot.com/2008/11/visit-to-hong-kong-yakult-co-ltd.html
Cancer Prevention and Intestinal Bacteria (I)
http://qualityalchemist.blogspot.com/2009/01/cancer-prevention-and-intestinal.html
Cancer Prevention and Intestinal Bacteria (II)
http://qualityalchemist.blogspot.com/2009/01/cancer-prevention-and-intestinal_23.html

Comparison between ISO/IEC 17025 accredited laboratory and GLP recognized laboratory

I would like to introduce the similarities and differences between GLP and ISO 17025 requirements as follows.

Scope:
GLP is developed for conducting non-clinical laboratory studies that support applications for research or marketing permits for products regulated by the FDA.

ISO 17025 applied to all laboratories where testing and/or calibration are performed and/or formed part of inspection and product certification. In principle, ISO 9001 is adopted in ISO 17025.

Similarities between both requirements:
i) Requirements on organization and personnel
ii) Requirements on equipment, sampling and validation
iii) Requirements on reporting / record and control of records

A schematic diagram showing the overlapping and specific requirements between an ISO/IEC 17025 accredited testing laboratory and an OECD GLP facility.

(Source: Engelhard T. et al., 2003)

The differences are shown in the following table.


ISO/IEC 17025 accredited laboratory has approximately 70% of the managerial and technical issues of the GLP directives covered, while 30% can be provided as an extension of the existing laboratory quality management system.

The simple checklists for preparing HOKLAS (Hong Kong Laboratory Accreditation Scheme) ISO 17025 accreditation and GMP audit are shown as follows:

Checklist for HOKLAS assessment:
1. Documents authenticating that the applicant laboratory is a legal entity or part of a legal entity
2. Quality manual & Operation procedure manual
3. Latest audit schedule
4. Summary of the findings of the latest quality and management system review
5. Test/calibration procedure manual(s)
6. Measurement uncertainty estimation
7. CV’s and copies of qualification documents for new nominees for signatory/operator approval
8. Laboratory floor plan
9. Laboratory organization charts, with key positions clearly identified
10. Sample test/calibration records
11. Sample test/calibration reports
12. Relevant proficiency test reports
13. Scope of accreditation to be assessed
14. Other documents (please specify)

Checklist for GMP audit (included GLP):
1. Business Registration Certificate
2. Floor plan
3. Organization chart, personnel qualification and signature record
4. Information sheet of key personnel (Authorized Person, QC manager and Production manager)
5. No. of full time and part time staff for manufacturing, QC and packaging
6. Full product list (with breakdowns of dosage forms & formulations)
i. Type of sterile pharmaceutical dosage (such as eye drops, single-dose injections, etc.)
ii. Other type of pharmaceutical dosage (such as tablets, capsules, powders, etc.)
7. List of major production equipment and QC equipment
8. Validation schedule of manufacturing processes and test methods
9. Stability study schedule
10. Others


Reference:
21CFR58: GLP for Non-clinical Laboratory Studies
ISO/IEC 17025: General requirement for the competence of testing and calibration laboratory
Engelhard T., Feller E. & Nizri Z. (2003) “A comparison of the complimentary and different issues in ISO/IEC 17025 and OECD GLD” Accred Qual Assur, Vol. 8, pp208-212.

Drug Recall and Related Testing Scope in Hong Kong Laboratories

The Department of Health (DH) has asked Europharm to recall Purinol tablets from the market as unacceptable laboratory analysis of the four Purinol samples taken from Queen Mary Hospital on 9 March 2009. The drug samples were tested by the University of Hong Kong and confirmed the presence of a fungus called Rhizopus. The significant of microbiology test of drug was concerned.

For controlling of Chinese medicines, the Chinese Medicines Section of the Government Laboratory was established in 1998, as well as the relevant analytic methods, to examine Chinese medicine for possible contaminants and adulteration of western medicine. In order to support the enforcement of the Chinese Medicine Ordinance and to demonstrate the competence in laboratories, the accreditation scheme of ISO/IEC17025 was also developed.

The Government Laboratory is the first laboratory accredited under HOKLAS for TCM in mid-2002, when the analysis of toxic elements in Chinese medicine namely, arsenic, cadmium, mercury and lead adopted microwave digestion followed by ICP-MS measurement. It aims to stimulate other local laboratories performing similar tests to seek accreditation thereby upgrading their testing standard. After that several commercial laboratories have accredited different testing scope in Chinese Medicine category.


The directory of accreditation is posted in HKAS website at http://www.itc.gov.hk/en/quality/hkas/hoklas/directory/chin.htm , where
1 – Government Laboratory
3 – The Hong Kong Standards and Testing Centre Ltd.
4 – CMA Industrial Development Foundation Limited
5 – Intertek Testing Services Hong Kong Ltd.
9 – SGS Hong Kong Limited
39 – Hong Kong Productivity Council – Environment and Product Innovation Laboratory
58 – Bureau Veritas Hong Kong Limited - Kowloon Bay Office
66 – ALS Technichem (HK) Pty Limited
83 – Wellab Limited
145 – Institute for the Advancement of Chinese Medicine (IACM) Ltd.

The summary of test scope for Chinese Medicine in Hong Kong Laboratories is shown in the following table.

Recently, the Department of Health (DH) invites Professor Yuen from Dept. of Microbiology in Hong Kong University to perform a feasibility study about the introduction of microbiology tests in pharmaceutical manufacturing industry.

Differences between ISO 9001, HKGMP and ISO/IEC 17025

What are the Differences between QMS standard in ISO9001, Hong Kong GMP and ISO/IEC17025 (HOKLAS Accreditation)? (1)

The worldwide-recognized Quality Management System is ISO9000 family. ISO9001:2000 is a generic standard for quality management system applicable to all organizations irrespective of type, size or product / service provided. However, many technical requirements are not stated in this generic standard ISO9001:2000 specifically. For instance, Cheung H.Y. and Chan L.W. (1998) presented that plant design for the manufacture of Chinese herbal pills is one of the more challenging activities in pharmaceutical industry, as it is the prime factor affecting the quality of a drug. Therefore, GMP legislative requirements can upgrade TCM products in Hong Kong(2). The design and implementation of team-based quality improvement campaign to Laboratory are also rose by Chin K.S. et al. 1996(3). Both industries are very concern about quality. Therefore, GMP Guideline:1995 and ISO/IEC17025:1999 are developed for herbal medicine industries and laboratories, which emphasis for the technical competence of both industries. Lau Edward P. (1996) stated that ISO 9000 is not well accepted by the pharmaceutical industry in the US (same as HK) for conventional therapeutic products because the mandatory regulatory practice, designs specifically for the industry, is superior to the ISO standards in many cases(4). The main clause comparison between ISO9001:2000, HKGMP:1995 and ISO/IEC17025:1999 (HOKLAS Accreditation) are summarized in Table 1.

The fundamental differences in the processes used by accreditation bodies and certification bodies to establish compliance with ISO/IEC17025 (HOKLAS Accreditation) and ISO9001 are obviously. Laboratory accreditation aims to recognize specific technical competence, the assessments of laboratories are conducted by teams comprising relevant technical experts and assessors able to evaluate not only the compliance with the management systems requirements of ISO/IEC17025 (or ISO9001), but also determining the specific technical competence of personnel and the availability of all the technical resources need to produce reliable data and results for specific test methods(5).

Reference:
1. Lai, Lotto K.H. and H.Y. Cheung (2003) “Laboratory accreditation has added-value for quality control of herbal medicine manufacturing but cannot replace implementation of good manufacturing practices.” Hong Kong Pharmaceutical Journal, 12(1), pp26-19.
2. Cheung H.Y. and L.W. Chan (1998), Planning and Designing a GMP Plant for the Manufacture of Chinese Herbal Pills, International Symposium on “The Worldwide Herbal Industry: Present and Future”, p16, July 15-17.
3. Chin K.S., K.V. Patri, K.F. Pun, W.H. Yeung, L.T. Poon and K.K. Poon (1996), Starting the Journey: Team-based QI in a University Laboratory, The TQM Magazine, 8(2), pp.20-25.
4. Lau Edward P. (1996), Pharmaceutical Quality Assurance and Quality Control Workshop, E.L. Associates, Inc., USA.
5. HKAS News, Hong Kong Accreditation Service, Issue No.33, January 2003.

Cancer Prevention and Intestinal Bacteria (II)

Carcinogen-producing bacteria (Digestive system)

Most of the bacteria in the intestine can be divided into two categories: lactic acid bacteria (feed on sugars/carbohydrates) and putrefactive bacteria (feed on proteins).

One theory holds that these intestinal bacteria transform fat into a carcinogen. Another possibility is that – since a person eating meat or egg takes in protein as well as fat – the proteins are being transformed into carcinogens.

Putrefactive bacteria (e.g. Bacteroides, E. coli, Veillonella, and Clostridium) break down proteins into ammonia, hydrogen sulfide, amines, phenol, and indole. Phenol and indole are known promoters of intestinal and other cancers. (They are also components of coal tar.)

A portion of the phenol is reabsorbed by the digestive tract and is detoxified in the liver, either by combining with glucuronic acid or sulfuric acid to form a harmless compound which is then eliminated in the urine; or by being released into the intestines and mixed with bile. The glucuronic acid compound with the bile is reconverted to phenol by the action of an enzyme known as beta-glucuronidase (It is most active in putrefactive bacteria such as E. coli and Clostridium welchii.), which is produced by some intestinal bacteria.

beta-glucuronidase formula

This circulation between the intestines and the liver (It is known as enterohepatic circulation.) indicates that some carcinogens are not eliminated, but remain in the body.

enterohepatic circulation diagram

Bile acids are the main ingredient of bile which aids in the digestion and absorption of fat. However, the remaining bile acids are not absorbed and returned to the liver, but flow into the large intestine. They are converted into secondary bile acids such as deoxycholic acid (deoxycholate) and lithocholic acid (lithocolate) by the action of Veillonella, Bacteroides, and other putrefactive bacteria. When the intestinal wall’s mucous membrane is stimulated by secondary bile acids, it changes appearance. This action is believed to raise the risk of colon cancer.

Lactic acid bacteria feed on sugars to produce lactic acid. Intestine dominated by lactic acid bacteria leans toward acidity that suppresses growth in putrefactive bacteria (which favor an alkaline environment). By weakening the influence of the putrefactive bacteria that produce carcinogens and induce enterohepatic circulation, Lactobacilli can play a significant role in improving the intestinal environment.

(The stool’s color is mainly from bilirubin, a reddish-yellow bile pigment produced in the liver from the hemoglobin contained in old red blood cells. Bilirubin’s color varies with acidity.
Acidic environment: Yellow
Neutral environment: Orange to brown
Alkaline environment: Greenish- or Blackish-brown.)

Reference:

Yoshio Aso (1997) “Lactic Acid Bacteria and Cancer Prevention” Shufunotomo

Cancer Prevention and Intestinal Bacteria (I)

I would like to share what I read from “How the lactic acid bacteria in your daily diet may inhibit cancer?” I will continue to study this topic because my father was found to have pancreatic cancer. It is sad that pancreatic cancer (last stage) cannot be cure but I believe the diet can help to prevent it.

How cancer grows?
Cancer is a mass of tumor cells and each cancer cell is a normal cell that has undergone a transformation.

Growth factors and growth inhibitory factors are proteins that message to multiply, and the latter to stop multiplying, so as to main the certain number of cell.

The so-called accelerator is known as the proto-oncogene that controls the functions of receiving messages at the cell membrane. The gene responsible for applying the brakes to the cellular proliferation process is the tumor suppressor gene.

How genetic malfunction produces cancer cells?
Gene in a normal cell (proto-oncogene):
1. “Antenna” intercepts extracellular message.
2. Messages are correctly transmitted to the cell’s interior.
3. After being scrutinized and processed, messages are transmitted to nucleus.
4. Another gene within the nucleus is activated and initiates and cellular proliferation process.

Malfunctioning gene (oncogene):
1. Malfunctioning “antenna” does not receive messages, but continues to signal cells to multiply.
2. “Antenna” transmits messages not received from outside.
3. Erroneous messages described in (1) and (2) are passed on to the nucleus.
4. The cellular proliferation switch remains perpetually in the “on” position.

The transformation of a normal cell to a cancer cell begins with the process by which a proto-oncogene becomes an oncogene. The process named initiation and anything that sets this process is known as an initiator. (e.g. viruses (hepatitis B & C); radiation; ultraviolet rays; cigarette smoke and automotive exhaust; and the chemical substances present in charred meat or fish.)

The next stage, extending from when a cancer cell develops until it begins proliferating, is considered a separate process. The process called promotion, and anything that instigates the process is known as promoter. (e.g. sex hormones, secondary bile acids, and chemicals such as saccharin, and artificial sweetener.)

Experiments have shown that vitamins C and E, as well as beta-carotent (a precursor of vitamin A) weaken the action of initiators, and that beta-carotent and vitamin A combat promoters within a cell.

One cancer cell does not constitute cancer
The smallest tumor detectable by various modern medical equipments consists of about a billion cells, weighs about 1g, and measures about 1 cm in diameter. (A cell weighs one one-billionth of a gram, even a growth of a million cancer cells weighs only about 1mg and is about 1mm in diameter.)

A stressful lifestyle or other factors can reduce the effectiveness of the cellular surveillance, rendering the body more likely to allow cancer to progress.

Reference:

Yoshio Aso (1997) “Lactic Acid Bacteria and Cancer Prevention” Shufunotomo

Biotech Lab General Requirement

The following information summarizes two types of laboratories requirements. The first one is a laboratory for microbiology test and the second one is for molecular biology test.

For Microbiology Laboratory, the facilities need to consider Biosafety Levels. WHO identified Risk Groups into 1, 2, 3 and 4. The table 1 is a classification of infective microorganisms by risk group.

Table 2 is relation of risk groups to biosafety levels, practices and equipment

Table 3 is summary of biosafety level requirements.

Code of practice
1. The international biohazard warning symbol and sign (Figure 1) must be displayed on the doors of the rooms where microorganisms of Risk Group 2 or higher risk groups are handled.
2. Only authorized persons should be allowed to enter the laboratory working areas.
3. Laboratory doors should be kept closed.
4. Children should not be authorized or allowed to enter laboratory working areas.
5. Access to animal houses should be specially authorized.
6. No animals should be admitted other than those involved in the work of the laboratory.

Fig 1. Biohazard warning sign for laboratory doors

Laboratory design and facilities for BSL 1 & 2.

1. Formation of aerosols
2. Work with large volumes and/or high concentrations of microorganisms
3. Overcrowding and too much equipment
4. Infestation with rodents and arthropods
5. Unauthorized entrance
6. Workflow: use of specific samples and reagents.
Examples of laboratory designs for Biosafety Levels 1 and 2 are shown in Figures 2 and 3, respectively.

Fig. 2 A typical Biosafety Level 1 laboratory

Fig. 3 A typical Biosafety Level 2 laboratory

The containment laboratory – Biosafety Level 3 is designed and provided for work
with Risk Group 3 microorganisms and with large volumes or high concentrations of
Risk Group 2 microorganisms that pose an increased risk of aerosol spread.

Fig. 4 A typical Biosafety Level 3 laboratory

The maximum containment laboratory – Biosafety Level 4 is designed for work withRisk Group 4 microorganisms. (It is not allowed in Hong Kong.)


For Molecular Biology Laboratory, the requirement to set up a PCR Laboratory is considered.

Development of the polymerase chain reaction (PCR) as a basic component of the molecular biology laboratory. The PCR laboratory typically is involved with activities that include sample preparation, PCR reaction assembly, PCR execution, and post-PCR analysis. Contamination prevention approaches are used in the PCR laboratory.

Fig.5 Outline of sample processing and analysis in a PCR laboratory.

Fig. 6 Organization of a PCR laboratory with separate pre- and post-PCR rooms.

Environmental Considerations

Air handling:
In the pre-PCR laboratory, there should be a slight positive pressure compared to the air in the connecting hallway. The post-PCR laboratory, in contrast, should be at slightly reduced pressure to pull air in from the outside and thereby prevent escape of amplicons from the completed PCR samples being analyzed inside the lab
UV irradiation:
It uses UV to sterilize the entire pre-PCR laboratory.
Protective clothing:
To further prevent PCR amplicons from leaving the post-PCR lab, each investigator should have a dedicated post-PCR lab coat. Additionally, each investigator should have a general molecular biology lab coat and a separate coat for pre-PCR.
Adhesive paper at lab entrances:
This approach effectively prevents trace amounts of dust and debris from entering the laboratory.

Reference:
1. Laboratory biosafety manual (Third edition) 2004: By World Health Organization
2. Setting Up a PCR Laboratory: By Theodore E. Mifflin (Department of Pathology, University of Virginia, Charlottesville, Virginia 22908)