Laundered Shop Towels: 13 - 100,000 workers using 12 laundered shop towels per day

If 100,000 workers using 12 laundered shop towels for 245 days per year for 40 years consumed 15 ug of lead each and every time the 12 towels were handled, we would expect to see one additional cancer as a result of that exposure.

If 100,000 worker using 12 laundered shop towels for 245 days per year for 40 years consumed 168 ug of lead each and every time the 12 towels were handled, we would expect to see how many additional cancers as a result of that exposure?

In my last post, I showed the formula CalEPA uses to calculate the NSRL - No Significant Risk Level - value of 15 ug/day of lead.  Here is how the CalEPA calculates that risk of one in 100,000 for the NSRL:

Source  Page 15

Doing a bit of algebra - I think that's what it's called - we switch the variables around so we can solve for "R"-  which is the cancer risk.

• R = (0.168 mg * 0.047 mg/kg-day-1) / 70 kg = 1.1E-04 or 1.1 in 10,000 or 11 in 100,000.

See!  11 times, just like Gradient said in Table 8a!

(Gradient 2011 Report)

Yes, but think about it for a minute....

What that ratio of "11" represents is this situation:

• 100,000 workers using 12 laundered shop towels per day for 9,800 days (245 * 40)
• 11,760,000,000 laundered shop towels containing an average of 100 mg/kg of lead
• 100,000 workers placing their hand to their mouth 11,760,000,000 times

Let those numbers sink in...check my math, I could have made a calculation error.

Notice what it would take to get 11 additional cancers in 100,000 workers for 100 mg/kg of lead?  11.8 billion laundered shop towels used, 11.8 billion times the worker's hand contacts the mouth.

Here is what ATSDR says about exposure and cancer, just so you can see that my logic is sound on this.

ATSDR extensively reviews literature linking exposure to compounds with cancer. The lowest level of exposure documented to cause any form of cancer in humans or animals is reduced by a safety factor of 100,000, which simply means if 100,000 people were exposed to this amount ofcompound 24 hours, everyday of their lives for 70 years, 1 extra cancer case might be expected above the normal rate of cancer in that population, i.e. 1 case in 100,000 above normal. (1)

The population here is workers.  So if you can honestly envision 11.8 billion laundered shop towels containing and average of 100 mg/kg of lead after being washed in soap and hot water, then dried under heat, a plausible situation, well I've got a bridge for you to buy!  And if you can see each of these 100,000 worker's bringing their hand to their mouth 11.8 billion times, well I've got land in Florida to sell you as well!

That ratio of "11" times higher than the NSRL uses Gradient's values and equation!

What happens if I use lead intakes calculated using more sound values?   In a previous post I made a case for throwing Gradient's equation out...

...and replacing it with CalEPAs hand to mouth equation.

Guideline for Hand-to-Mouth Transfer of Lead through Exposure to Consumer Products: 2011

The CalEPA equation calculates the daily total intake.  The intake is divided by 70 kg (weight of an adult) to derive a mg/kg-day intake value. (See post)

• Intake = 0.0013 mg/cm2 x 19 cm2 x 0.5 x 1.5/hour x 8 hours =  0.148 mg per work day
• 0.148 mg per day = 0.148 / 70 kg =  0.0022 mg/kg-day Intake or 2.2E-03 mg/kg-day

Using Gradient's EF of 245 days, an ED of 40 years, and an AT of 25,550 days (70 years) we would modify the CalEPA calculation as follows:

• (0.0022 mg/kg-day * 245 days/year * 40 years) / 25550 days = 8.4E-04 mg/kg-day
• 0.00084 mg/kg-day * 70 kg = 0.06 mg-day

Using CalEPA's hand to mouth intake formula, a worker using twelve laundered shop towels per day for 40 years would have a lead intake of 0.00084 mg/kg-day over a 70 year period of time.

Placing that intake into CalEPA's cancer risk calculation, the "R" cancer risk would be:

• R = (0.06 mg * 0.047 mg/kg-day-1) / 70 kg =  4 in 100,000.

Using Gradient's values - with the exception of the hand to mouth transfer rate - the excess cancer risk from using 12 towels per day containing 100 mg/kg of lead for 40 years is 4 additional cancers per 100,000 workers.

So whatcha think?  

Is 11.8 billion shop towels with 100 mg/kg lead a plausible scenario?  Will 100,000 workers place their hand to their mouth 11.8 billion times?  Is this really an exposure situation where one would ask a worker who is using a laundered shop towel:  "Why risk it?"

Source

As I stare into that baby's eyes I have no problem telling that dad, go ahead and use laundered shop towels. If lead is the baddest metal they found, go ahead and use a laundered shop towel all you want.  Heck, you can even use it while drinking apple juice!

Next post: Laundered Shop Towels: 14 - Should you believe them?

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