Exposure


Confession: I missed the assessment of this hazard the first time.

Awhile back I performed air sampling during aluminum welding. The welders were cordial and let me crawl over their welding equipment, poke around old boxes of wire and metal stock. I did not think there were any “real” hazards. We did find some airborne levels of various metals. From the picture can you tell who did the most welding?

welding mce

After I had performed the sampling and the report was sent, I was asked if I had checked for ozone (O3)? I admitted I hadn’t and asked if it was an issue? Well, apparently it is (or rather, might be).

I went back to the shop, begged for another chance, and performed ozone sampling. It wasn’t difficult, but eating crow was the hardest part.

More information on the subject can be found at: NIOSHUK- HSE. Ozone is formed when the UV radiation hits oxygen. The ACGIH TLV is variable (see table below)ozone acgih, and the OSHA PEL is 0.1 ppm.

Health: Ozone, O3, can cause lots of different respiratory illnesses. These can include a decrease in lung function, aggravation of asthma, throat irritation/cough, chest pain, shortness of breath, inflammation of lungs, and a higher susceptibility to respiratory illnesses. ACGIH classifies it as an A4, or not a suspected carcinogen.

Luckily the results were found to be non-detectable (“IH talk” for none-found). Which only means I didn’t find it, not that it is not there. I sampled for a long time (530 minutes) because they were working 10 hour shifts. But, they only welded for a total of approximately 1.5 hours during that time.

If welders are in a confined area, or a small space with limited ventilation, the results might be significantly different.

 

Instead of explaining how to calculate safe levels of chemical mixtures, this will be a reminder.

The American Conference of Governmental Industrial Hygienists (ACGIH) in their Threshold Limit Values (2014), has an excellent explanation of how to calculate a safe level of exposure. However, in summary, if separate chemicals have the same health effects (effect the body in the same way), they may do three things:

  1. Additivity – the sum of their exposure & health effect is A+B. More on this below.
  2. Synergy – the sum of their exposure is MORE than A+B. This is bad, and hard to calculate.
    • Similar in principle to smoking and asbestos. If you smoke and have asbestos exposure, you are worse than just the additive.
  3. Antagonism – the mixed chemicals cancel each other out. It usually never works this way.
    • But, as a terrible example, it would be like acid rain dissolving styrofoam. (I don’t think that’s true, BTW)

Back to Additive (Additivity):additive

If two chemicals (or more) in a mixture have similar health effects (central nervous system, or effect the kidneys, for example), then, until you know otherwise, you should assume they have additive effects. Have your favorite Industrial Hygienist use your air monitoring data to calculate the additive effects using the ACGIH Additive Mixture Formula.

This is useful for combining both full shift air monitoring data, short term, and ceiling exposures. Extreme caution should be used if the chemicals are carcinogenic (as low as reasonably achievable (ALARA) is best here), or if they are complex mixtures (diesel exhaust).

It’s a bit confusing, but worthy of reminding ourselves of chemical mixtures.

This hazard is somewhat difficult to understand. There are number of reasons for the confusion, but the easiest way to explain it is to realize that:

Summary:

Diesel exhaust = Diesel particulate matter (DPM) = lots of different chemicals & particulates

AND: There is not a perfect way to measure the exact exposure.

The Long Story:

The term ‘diesel particulates‘ includes the following (not a comprehensive list):

  • elemental carbon (the most reliable method for testing occupational exposure to exhaust, Birch & Cary 1996)
  • organic carbon
  • carbon monoxide (CO)
  • carbon dioxide (CO2)
  • hydrocarbons (PAH)
  • formaldehyde
  • oxides of sulfur & nitrogen

You can quickly see that these are very different substances, and to make it more confusing, you can change the amounts by:

  • the fuel (on road/off, low emission fuel, biodiesel)
  • the motor type
  • the tuning of the motor (& dynamic versus idle), new motor restrictions
  • scrubbers, etc.

In addition, there are not any well-established occupational exposure limits specifically for diesel exhaust. However, the International Agency for Research on Cancer has classified “whole diesel engine exhaust” as a carcinogen (cancer causing), so there is reason for concern. Most of the research and rules are in the mining industry, which uses a lot of diesel equipment and the exhaust really has no where to go.

  • OSHA = none, but they have a hazard bulletin, and of course, some of the components have exposure limits
  • MSHA = 0.4 mg/m3 for total hydrocarbons and 0.3 mg/m3 for elemental carbon
  • Canada (CANMET) for respirable combustible dust (66% of respirable dust in mines is from diesel exhaust) = 1.5 mg/m3
  • ACGIH = none (for now)
    • 1995 proposed 0.15 mg/m3 (for diesel particulate matter)
    • 1996 proposed lowering it to 0.05 mg/m3 (for diesel particulate matter)
    • 2001 proposed a different limit of 0.02 mg/m3,
      • but for elemental carbon and
      • said it was a suspected carcinogen
    • 2003 withdrew proposed limit- citing not enough scientific information

Bottom line:

  • control the exhaust & where it goes (better fuel, better mechanical, scrubbers, ventilation).
  • most exposures to diesel are below the (now retracted) ACGIH TLV of 0.02 mg/m3 (or 20 ug/m3) (Seshagiri & Burton, 2003).
  • If you have a confined area, unusual concerns, or a particularly stinky situation; measure for multiple parameters (CO, CO2, elemental carbon and maybe NOx, and SOx). Compare these to their respective limits and classify the exposure (describe the conditions)

The latest push from NIOSH is ridiculous, in a bad way. It’s titled, “Recognizing N95 Day” on September 5. I’ve written about these types of respirators before.

Let’s start with:n95 box

  • NIOSH estimates 20 million workers exposed to airborne health risks
  • N95 (s) are the most commonly used respirator
  • NIOSH certifies all respirators. And, OSHA requires all respirators to be certified by NIOSH
  • All certified respirators must have an “assigned protection factor”, which is a level of protection they are able to achieve
  • N95 respirators are certified to provide a protection factor of “up to” 5 times the exposure limit

For the record, I am not disputing how NIOSH certifies respirators, or if these respirators can achieve a protection factor of 5 (5x the exposure limit). I will also add that in the healthcare setting (hospitals) these might have a useful role.

Here’s the problem:

  • If you need a respirator, you would NOT choose a N95. They are terrible fitting.
    • To put it another way: if you had to work in an environment which had a dangerous airborne hazard, would you CHOOSE this respirator?
    • Or another way: “There is a chance this N95 respirator might protect you, wear this just in case”. (?)
  • If you have fit tested these types, you know they are hard to fit, and at best, mediocre in their protection. At times it is hard to fit test a tight fitting 1/2 face respirator on someone who is clean shaven.
  • N95 respirators are handed out (like candy) at construction sites for any task which “may be hazardous”.
  • Let’s be honest:
    • these are “comfort” masks. AKA:  peace of mind, not for protection.
    • these are cheap. That is why most employers buy them.
  • And, let’s mention:
    • exposure levels can vary (have you measured the worst case scenario?)
    • change out schedule? Do your workers wear the same respirators every day? Do they change them when they start getting hard to breathe?
    • facial hair (no one who is on a jobsite has this, right?)
    • there are knock-off N95 respirators which actually aren’t certified (they’re fake)

In this instance I wish NIOSH would spend money on training people to use the correct type of respirator. Or, how to adequately measure the hazards found at various sites.

As a quick review. If you need to wear a respirator, here are the proper steps.

n95 box2

I am ashamed I have not written on this topic yet. In fact, this issue is so close to me, it bewilders me why I never connected it to occupational exposures. It’s even a carcinogen, and I try to get as much of it as I can when it is around.

To summarize my personal examples:

  • My dad has skin cancer on his ears and annually has these removed.
  • My next door neighbor died in 2009 from skin cancer (metastasized). He was a county construction worker for 35+ years and was in the sun, with his shirt off. A LOT.

More recently:

There are some chemicals and foods, when taken/exposed, actually make you more sensitive to the suns UV exposure (aka: photosentisizer). A list can be found here. Some of them are:

  • foods: carrots, dill, clover, eggs
  • medicine: antibiotics, diuretics, high blood pressure
  • chemicals: coal tar (creosote), benzene, xylene
  • cosmetics

And, if you haven’t noticed, construction workers get a lot of sun exposure, especially in the summer. Don’t forget, welders can have high exposures, and our heavy highway (road paving) crews are exposed to coal tar pitch. We talk about heat stress, but we should talk about the long term effects of skin damage.

There are no specific OSHA regulations on UV exposure. However, there are some guidelines from the ACGIH. There might be an instance where we can work within our “hierarchy of controls” and and eliminate the exposure to the employee. However, with this hazard, rather than working on eliminating the hazard, I would recommend we provide PPE.

Do you provide sunscreen to your employees?

It is officially summer and construction road crews & roofing is in full swing. Some projects require the use and application of coal tar pitch. Not only is it stinky, it is is hazardous.

Here’s some info:

  • Uses
    • Roofing
    • Asphalt seal coating
    • Pharmaceutical treatment for psoriasis (scalp/skin condition)
    • Graphite industry (in the production of graphite)
  • General
    • Coal tar pitch is actually a make-up of a bunch of different substances (maybe even 10,000 of them)
    • Contains lots of polycyclic aromatic hydrocarbons (PAHs) and other chemicals including: benzene, pyrene, benzo(a)pyrene, phenanthrene, anthracene
  • Exposure
    • can be exposed by inhalation, ingestion (is this likely?), or exposure to skin, eyes
    • considered a carcinogen if the product contains more than 5% of coal tar
    • cancers include: skin, scrotal, lungs, bladder, kidney & digestive
    • increases your sensitivity to sunlight (easier to sunburn)
  • Safety
    • Pick a sealant/coating that does not contain coal tar. A list of some can be found here.
    • Avoid inhalation & skin/eye contact
    • Train your employees. A sample safety SDS (MSDS) can be found here.
    • Wear the correct PPE.
    • Air sample to determine exposures. OSHA has a method (58).
  • Resources

asphalt

This question gets asked a lot, and in many different ways. Such as:asbestos iron

  • Will I get hurt if I touch asbestos? (aka: How long can I be exposed?)
  • What if I have done siding removal/cutting pipe/removed TSI (etc) on an asbestos containing product, am I safe?
  • If I am only doing going to do touch asbestos for 20 minutes (or ___ time), will I still be in compliance?
  • I am disturbing less than 3 square feet of asbestos, I can do this legally, right?

The answer is:   it depends.

Or, an alternative answer: if you think you are disturbing asbestos; you’d better verify (by performing an air sample).

Nowadays there is no excuse for exposing employees, tenants, neighbors to asbestos. And, really, if you are working with asbestos, you need to be extra diligent to inform everyone about the hazard. The worst situation isn’t from a single exposure to asbestos, or an OSHA fine. The worst situation is this:  when you don’t pre-plan, and then verify your exposure levels. Because, someone will make up a worst case scenario, and at that point, you are already behind.

 

 

Noise has some interesting health effects. Most people assume the worst that can happen is you will lose part of your hearing. However, a recent (March, 2014) study in Injury Prevention by Girard, et.al, concluded that those employees exposed to loud noise (above 100dBA) were admitted to hospitals more frequently, and at risk for other injuries.

Some other known health effects include (from Medscape & WHO):haul truck toy

  • fatigue
  • impaired concentration
  • behavioral changes
  • irritation
  • impaired academic performance
  • interrupted sleep (during sleep times)
  • changes in endocrine & autonomic nervous systems
  • increase in heart rate, blood pressure, vasoconstriction
  • sexual impotence
  • neurosis
  • hysteria

Noise is a simple subject, but there are many factors which influence noise exposure to individuals. Some include:

  • The individual: age, prior exposure
  • The noise: loudness (dB), type of noise (Hz), distance from noise
  • Time: exposure vs. non-exposure time per day

More information on how to control this hazard in construction can be found here.

And, as a bonus, the Journal of the Acoustical Society of America has published a review of the top Smartphone Sound Measurement Apps..  The winner (most accurate) was SPLnFFT, at only $3.99. A close runner up was SoundMeter by Faber. Another summary review is here, and here.

Can we measure an exposure accurately with just one sample? (statistically, no.) Also consider: Can we measure a “worst case” scenario and be OK for the rest of the project? (again, hypothetical question)

There was a blog post, here by Mike Jayjock, which reminded me of how silly our data points (aka industrial hygiene sample results) are in the big picture of statistics.  I’m slowly reading a book titled, “Control Banding” by David Zalk who is with Lawrence Livermore National Labs. The CDC also has a section on control banding here.

Another side of this is a common practice we all perform called Risk Analysis. There is much on the subject, but essentially it’s similar to triage at an emergency room. What is the easiest, best thing you can do: given what you have available and what you are able to muster?safety triangle

Too often (myself included) we perform air monitoring for a specific situation and use that information as the gospel-truth. Well, this might be like living in the United States and never traveling. We meet a very nice person from the Ukraine. They seem very typical Eastern European and have a thick accent, but are they really like everyone in Russia? Is this person typical? Are they exactly like every other person from Russia?

This type of stereotyping is the same as taking one sample and drawing conclusions about all exposures. You might be right, BUT…you might be wrong.

There is a fun app you can download called, IH DIG by Adam Geitgey (Apple & Android).  This app illustrates the importance of using statistical tools, rather than guessing. (It’s a game)

Sorry I do not have many answers in this post, just a lot of questions.

Construction workers falling is the number 1 cause of death in this industry (residential & commercial).

NIOSH has published a prevention through design (PtD) document for those who design parapets to prevent falls. This document is new. But the principle of it has been around since Moses’ time: “When you build a new house, make a parapet around your roof so that you may not bring the guilt of bloodshed on your house if someone falls from the roof.” Deuteronony 22:8. 

Another good resource: Stop Construction Falls .com. They even have an interesting map which shows where they occur.

The CPWR obtained a NIOSH grant and has some free videos here.

map of falls

Spring is when the work picks up, be safe out there.

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