Tag Archives: risk assessment

Risk Reduction Engineering for COVID-19

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In response to some discussions I had seen about the use of HEPA filters to help with the COVID-19 crises, I wrote some thoughts on how effective I thought HEPA might be. Several people on Twitter stated they agreed with my statements. An HVAC technician (@JSTootell) provided some thoughts that I had never even considered such as the energy requirements on the buildings where a HEPA filter is installed as HEPA requires more energy (i.e. electricity) to run than normal HVAC filters. He also said the normal air velocity is super low because if you increase the air velocity and hence get more circulation, people complain about the noise of the air through the vents.

Some others have noted that HEPA filters, on a whole HVAC system or portable units in each room, won’t hurt to which I agree. One said they should be a part of a multiple layer approach to prevent the spread of COVID-19 to which I also agree. In fact, while I did not say it, that is part of my argument, HEPA filters alone will not solve the problem of COVID-19 transmission. I want to take a step back though and discuss this from an engineering perspective.

The basic, general idea in engineering is you find out what your design specifications are, you make some calculations and draw some designs to comply with those specifications based on proven information, you throw in some safety factors, and then you build whatever it is to comply with your design and calculations. If you want to build a bridge, you need to know before hand what are the design specifications. Is it for trains, vehicles (cars and trucks), pedestrians, or something else entirely? How many of the intended type of users will be crossing the bridge daily? What is the span of the bridge? What is the height of the bridge? What type of weather will the bridge will be exposed to? There are far more questions, but that is the general idea. You can’t design a bridge until you know what you are designing.

I currently work in human health risk assessment related to exposure to hazardous chemicals. It is not the same as risk assessment related to exposure to infectious agents, but there are similarities. With hazardous chemicals, the goal is to reduce people’s exposure such that they are not at undue risk to the chemical exposure. You can’t reduce risk to zero; it is simply impossible. With chemicals that cause cancer, generally you are trying to get the risk below one in a million chance of cancer caused by exposure to that chemical. Another part of this is who is at most risk. With chemicals, the people we are generally most concerned with are children or pregnant women as they can be more susceptible to harmful effects than healthy, non-pregnant adults. The risk requirement is one of your design requirements. If a person can be exposed to 100 mg/l per day (via ingestion) or 100 mg/g (via inhalation) of a certain chemical and not be above one in a million risk of cancer, then you have to figure out what needs to be done at a contaminated site or with contaminated drinking water to get their exposure (and thus risk level) below that number. This could mean filtering water or removing topsoil at site (to avoid incidental ingestion of contaminated soil or to avoid breathing in soil particles). What kind of treatment and how much treatment is needed to get below that concentration? That is one of your design requirements. Similarly the design and operation of water treatment plants is based on cleaning water such that the water has less than some amount of a contaminant before it is sent via pipes to the customers. Design requirements from water treatment plants is generally based less on risk calculations and more on state and federal requirements for contaminant levels in drinking water. These federal requirements are called Maximum Contaminant Levels. Water treatment plants must meet these requirements, and they are designed to prevent the people who drink that water from getting sick from microorganisms or chemicals in the water.

This leads me to designing a HVAC system with HEPA filters or the use of portable HEPA filters in buildings to protect against COVID-19. In order to design a system, you have to know the design requirements. It is absolutely fine to say you want to reduce virus particles in the air and reduce transmission, but that is not a design requirement. Reduce is a vague, qualitative word. Engineering requires quantitative requirements. If you only want to reduce particles in the air, then you will only reduce the risk by an unknown amount with no clarity on if that reduction is an acceptable amount to the occupants of the building. Reducing risk could mean that instead of 30% of the occupants of a building getting sick, only 20% do. I personally don’t find that to be an acceptable reduction. A design requirement is based on what concentration of virus particles can be in the air and no person gets sick from COVID-19. Perhaps your requirement would not be that stringent, perhaps you would be ok with one in a thousand people getting sick from COVID-19 based on the design. The design requirement can be based on people wearing a mask or not wearing a mask. Maybe with everyone wearing a mask indoors, they can be exposed to 10 virus particles per hour, but without a mask, they can only be exposed to 2 virus particles per hour. This is where infectious disease experts are needed to provide information as to the pathogenicity and virulence of the pathogen, which in this case is COVID-19. An engineer designing a HVAC or some other filtering system for a building is not the person to decide what those design requirements are. They need the infectious disease experts to state what concentration of a pathogen a person can be exposed to without getting infected. The concentration may be zero. The problem at this point is I don’t think we know how much COVID-19 a person can be exposed to without getting sick. Thus, if we don’t know how much COVID-19 a person can be exposed to without getting sick, how can we possibly design a system to prevent a person from getting sick.

I can already hear arguments that we just need to do something. We need to accept some risk but do some things to reduce risk, so we can get things back to normal. I don’t think most business owners are going to be willing to spend a non-negligible amount of money on some design that will simply reduce risk to an unknown and unproven amount. For a place of employment or a school, is it reasonable to ask people, especially children, to return to a building with an unknown risk if a system has been put in place that reduces the risk an unknown amount? How much money should employers and educational boards spend to reduce risk an unknown amount? If you are willing to accept some risk, then why spend money on something that may reduce risk by some unknown amount? Everyone is already spending money on masks, gloves, hand sanitizer, etc. which at least has been proven to reduce risk, but not eliminate it, by a reasonable degree from a cost benefit perspective. I spent $20 or something on two reusable cotton masks that I wash after use. That is a very reasonable cost benefit amount from my perspective even though I can’t calculate the risk reduction of the mask. How much money is reasonable to invest in either a whole system HEPA filter or portable HEPA filters when the risk reduction is unknown? An extremely quick internet search provides options for portable HEPA filters from $200 to $1200. Should schools buy one per classroom, even at the low price end, when there is no data to show they would reduce risk at all? The point is, reducing risk is good, but if you going to invest money to reduce the risk, it would be prudent to determine how much the risk is actually going to be reduced before you do it.

Science, the Media, Graphics, and Communication

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Recently, I had my annual performance review at work, and one of the things my boss said I needed to work on was communication with upper management in the form of not realizing they don’t know what I think everyone knows. I fully admit that there are some things so engrained in me that it would never dawn on me that other people do not actually know those things. Perhaps it is a reaction to the fact that I HATE being talked down to. I hate when people attempt to explain something to me I already know. The more basic the fact the more I hate it. It feels insulting. I hope those people where I have to go back and explain at a lower level, take it as a compliment, as it kind of is. I sometimes assume they already know things, and while I will correct it when necessary, it really is a compliment that I assume someone knows something they don’t. However, I do understand what my boss was saying, and science communication is something a lot of scientists talk about a lot. How can scientists improve science communication so that non-scientists can understand science, especially since science concepts sometimes are complicated?

So in one of those striking coincidences, the same day I have my performance review, the World Health Organization (WHO) comes out with a report that says that processed meat is carcinogenic to humans. The blog post is not meant to go into a discussion of how badly this report was blown out of proportion by much of the media. I will just say there is a difference between relative risk and absolute risk. This Forbes article I think does a pretty good job of explaining what the WHO said and also what it means, and this post by Cancer Research UK is really good and has wonderful graphics explaining risk. I will also say I am not a vegetarian, and although I really don’t eat that much red meat or processed meat, I don’t have a thing about bacon, but I spent a good part of childhood in Texas, and God bless Texas barbecue, meaning brisket so tender no knife is needed, and now I am hungry. I’m sorry where was I? Oh right, WHO and processed meat. So what I did want to say a few words about was a graphic I saw on NBC Nightly News, mainly the image below (which in case it is not obvious, I literally took a photo of my television screen).

Screen shot of NBC Nightly New with Lestor Holt on 10/26/2015

Screen shot of NBC Nightly New with Lestor Holt on 10/26/2015

I am not an expert on asbestos, but I can say with confidence that a smokestack is NOT where asbestos originates. Asbestos is a naturally formed mineral, and in some locations, you can be exposed to asbestos from the natural soil and rock near you. Where people generally get asbestos exposure is old house insulation, old pipe insulation, car brake pads, and a whole lot of old building material. I posted this photo on Facebook yesterday because I was just kind of flabbergasted. It leads me to questions like does NBC News seriously not know where asbestos comes from? Are they just too lazy to find a better graphic? One Facebook friend said that maybe they used a smokestack to designate a generic industrial process. I replied that by that analogy cigarettes should also have a smokestack because they also come an industrial process. Asbestos does not originate from an industrial process. It originates from the earth, but it was then used by industry into various products. The other two graphics imply where your exposure to the named carcinogen would be. Your exposure to asbestos is not from a smokestack. It is from old building material like insulation. They could have had a graphic of fibrous pipe insulation. They could have also just had a graphic of fibers to show what asbestos looks like under a microscope. I feel confident that with a short period of time and a graphic designer, we could have come up with a factually correct and simple asbestos graphic. One may very well already exist. This reply led to a bit of a discussion between my friend and I that was partially about science communication. In short he said that because my reply was so long explaining the problems with the graphic, that he stood by his opinion that the graphic was fine. I acknowledge that my reply was long, but I was not wrong on any points. Also the NBC graphic was just plain bad. A smokestack does not in any way represent asbestos. Worse than that it provides incorrect information to an uninformed viewer who might think that a smokestack is in fact where asbestos exposure comes from.

I very much respect the points my friend made, and he did state something that gets at the heart of a problem I often have, which is brevity. [How long is this blog post now?] I have a tendency to give long answers, which I understand can be annoying to management or anyone else, who wants a short answer. The reason I sometimes give long answers is that the answer is not simple, or I need the question defined better in order to give a simple answer. I just can’t bear the idea to give an incorrect answer. I can’t bear to give a short answer to management then have someone come back and say well what about “this”, and management to come back at me and say well what about “this.” I work in complicated subjects. Very often the problems, the solutions, the questions, and the answers are all complicated. The problem with the media sometimes is they try to make a complicated subject simple and sometimes fail miserably. Sometimes they just have no clue what they are talking about and seem to refuse to want expert advice. I respect journalists who can take complicated science subjects and explain them simply. There is a difference between explaining something simply and accurately and explaining something simply and wrong. Asbestos coming out of a smokestack is simple. It is also wrong.

Formaldehyde in Baby Shampoo: Cancer or Sensitivity Issue?

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An article was recently published in Slate about Johnson & Johnson reformulating its baby shampoo to remove formaldehyde. The article discussed how some people’s somewhat misguided fears about a known carcinogen, formaldehyde, caused its removal from baby shampoo, when in reality if you are worried about carcinogenic exposure to formaldehyde, baby shampoo should be the least of your concern. As the article’s author, Tara Haelle, correctly points out, formaldehyde is a naturally occurring substance. It is produced in normal atmospheric reactions and when wood burns, both during natural forest fires and human caused fires. It is also produced during anthropogenic activity from numerous industrial processes and petroleum fueled combustion, i.e. cars, ships, airplanes (Salthammer et at. 2010).

I have a few issues with this article, however. First, it states “high enough doses of inhaled formaldehyde can cause cancer, leading OSHA and the EPA to set limits for safe exposures.” Second, it quotes two chemists who say in different ways that the toxicity of a chemical is related to its dose or the amount of exposure, and it essentially states that formaldehyde only causes cancer in high doses. Finally, it completely fails to mention another reason why formaldehyde may have been removed that has nothing to do with cancer.

The problem I have with the second point, is that formaldehyde is a carcinogen, and the toxicological theory with carcinogens, is that exposure to one molecule of a carcinogen can theoretically cause cancer, depending on the carcinogen’s mode of action. With non-carcinogens, it is appropriate and scientifically accurate to say that the dose makes the poison. There are substances that to be healthy you need in some dose, but exposure to too high of doses can lead to detrimental health effects, for example iron and a whole bunch of metals. There are others that you don’t need at all, but you can be exposed to a certain dosage with no ill effects. However, with carcinogens depending on the mode of action for the carcinogenicity, it is believed that there is no safe level of exposure. In theory, all it takes is one molecule to cause a cell to multiply out of control and cause cancer. This is where the carcinogenic mode of action is important. The carcinogenic mode of action refers to how a particular carcinogen actually causes cancer to be initiated. If, for example, a carcinogen’s mode of action is mutagenicity, like radiation, then exposure of any dose can potentially cause the effect that leads to cancer. Thus, there is considered to be absolutely no safe level of exposure to that carcinogen. Each additional exposure increases your risk of getting cancer. However, there are other carcinogenic modes of action, and carcinogens with certain other modes of action would be considered to have a exposure threshold below which no cancer would occur.

So what about formaldehyde? What is its mode of action for carcinogenicity? Is there a safe level of exposure below which there is no risk of cancer? In the US, that appears to be in debate. This brings me to my next point. It is misleading, and in my opinion just plain legally and scientifically incorrect, to state that OSHA and EPA set limits for safe levels of exposure. The EPA has calculated formaldehyde’s Inhalation Unit Risk (IUR) for cancer to be 1.3 x10-5 per µg/m3. “EPA estimates that, if an individual were to continuously breathe air containing formaldehyde at an average of 0.08 µg/m3 (8.0 x 10-5 mg/m3) over his or her entire lifetime, that person would theoretically have no more than a one-in-a-million increased chance of developing cancer as a direct result of breathing air containing this chemical.” The word “increased” is important. It means that it is already assumed that there will be a certain number of cancer cases, and this concentration would cause additional cases above background. Furthermore, EPA states that for calculation of cancer risk from formaldehyde exposure, a linear approach with a multistage procedure due to additional risk at higher concentrations should be used. A linear approach means that any exposure causes a cancer risk with each exposure increasing the risk, and the multistage procedure means that high concentration exposure causes risk to increase at a greater rate. A linear approach is the more conservative method with carcinogens and is normally used when there is not enough scientific evidence to devise a threshold or a different risk method. With that being said, EPA is currently reviewing its toxicity assessment for formaldehyde, and it is possible when that assessment if finalized, EPA will change it cancer risk approach. With respect to OSHA, they have set an permissible exposure limit (PEL) at 0.75 parts formaldehyde per million parts of air (ppm) as an 8-hour time weighted average. The reasoning behind this level is complex, but in part, they state “this PEL represents OSHA’s best judgment of the exposure limit, along with the ancillary provisions, necessary to eliminate a significant risk of harm to employees.” The phrase “significant risk” is in there because their calculations, like the EPA’s, involve uncertainty and probabilities. They are not stating that below the PEL there is no risk, it is just not as significant. Neither OSHA or EPA is stating that below some level of exposure, formaldehyde will not give you cancer. They are stating it unlikely or insignificant compared to a background cancer risk. Below the set levels, the risks are really low, but they still exist.

Back to the baby shampoo. I do, in fact, agree with the point of the article that formaldehyde in baby shampoo is not a concern for cancer. However, I would not state it will not cause cancer. I would state that possible formaldehyde exposure in baby shampoo is highly unlikely to cause cancer. An additional point, which is not in the article, is that formaldehyde is not readily absorbed through the skin, and the amount of volatilization of formaldehyde, which could then be inhaled, from baby shampoo is likely to negligible.

With all that being said, I don’t necessarily agree that removal of formaldehyde from baby shampoo is a case of chemophobia and an overblown reaction by a company. It is possible that Johnson & Johnson removed formaldehyde not because of cancer concerns but because formaldehyde is a known sensitizer and allergen. Many skin care products contain formaldehyde or formaldehyde-releasing preservatives, which include quaternium-15, diazolidinyl urea, DMDM hydantoin, imidazolidinyl urea, bronopol, and tris nitro. While only a small percentage of people have a sensitivity or allergy to formaldehyde, for those that do, it is safest to avoid any exposure. Whether or not baby shampoo containing formaldehyde could cause a person to actually develop a sensitivity or allergy is another subject.

I have no idea why Johnson & Johnson actually decided to remove formaldehyde from baby shampoo, other than that it was a business decision. However by removing formaldehyde, regardless of any cancer concerns, there is now a small but real percentage of potential consumers who can buy their baby shampoo without concern of skin reactions due to their formaldehyde sensitivity or allergy. Thus assuming there is another safer preservative that can be used in place of formaldehyde, its removal would seem, to me at least, to be a good business decision, as they have increased their customer base to people with certain skin sensitivity and allergies.