ASHRAE Journal - June 2014 - 42

Column Iaq applIcatIons

Significant Risk Levels (NSRLs). The NSRL is the 70 year
average daily intake level calculated to result in one excess
case of cancer in an exposed population of 100,000. For
non-cancer health effects, we used the California Office
of Environmental Health Hazard Assessment5 Chronic
Reference Exposure Guidelines (CRELs).
For propylene glycol and nicotine, which do not
have established CRELs, we used 1% of the California
OSHA6 occupational eight-hour Permissible Exposure
Guideline, and for lead we used the Environmental
Protection Agency7 National Ambient Air Quality
Standards (NAAQS), three-month average requirement.
For both the direct and indirect exposures, we calculated the hazard quotients as the ratio of the calculated
exposures to the cancer (NSRL) and non-cancer (CREL)
health exposure guidelines. Hazard quotients in excess
of 1.0 indicate a health risk.
Table 2 summarizes the hazard quotients associated
with the direct exposures of e-cigarette users and the
indirect (passive) exposures of non-users.
With respect to the NSRL hazard quotients for cancer

www.info.hotims.com/49805-43
42

ASHRAE JouRnAl

ashrae.org

J u n e 2014

related health effects, four of the nine chemicals analyzed exceeded 1.0 for the direct exposure to users; lead
(1.33), formaldehyde (1.64), NNK (2.36), and cadmium
(5.13). For the indirect exposure to non-users, the NSRL
hazard quotients were all less than 1.0, with the highest, cadmium (0.12). With respect to the CREL hazard
quotients for non-cancer related health effects, three of
the nine chemicals analyzed exceeded 1.0 for the direct
exposure to users; acrolein (7.0), nicotine (222), and
propylene glycol (967). For the indirect exposure to nonusers, the CREL hazard quotients also exceeded 1.0 for
nicotine (5.4) and propylene glycol (23).
If we use the minimum rather than the maximum
chemical emissions in Table 1, the modeled direct and
indirect CREL hazard quotients still exceed 1.0 for propylene glycol (293 direct and 7.0 indirect) and nicotine
(65 direct and 1.6 indirect).
With respect to the modeled indirect exposures, we note
that while this was a worst-case exposure scenario with a
low ventilation rate of 0.3 h-1, even if ventilation rates are
tripled to 0.9 h-1, which exceeds ASHRAE Standard 62.18
default minimum ventilation of 0.78 h-1 for the modeled office space, the indirect exposures still present a
significant health risk. Ventilation rates would have to be
increased by a factor of 23 to mitigate the health risks for
each of the nine chemicals modeled. Clearly, ventilation is
not a solution and e-cigarette use will have to be regulated
indoors in the same manner as is done for tobacco smoking, which is prohibited indoors.
We also note that there has been little research into the
emissions of the flavorants that are added into the e-cigarette fluids. Some flavorant chemicals, such as diacetal,
while having no apparent adverse effects when ingested,
when aerosolized and inhaled can cause lung irritation.
Like the flavorants, the propylene glycol carrier,
while used as a preservative in food products without apparent adverse health effects, are themselves
a potential airborne respiratory irritant. Wieslander
et.al.9 conducted experimental studies of 27 individuals exposed to propylene glycol aerosol for a one-minute
period with airborne concentrations ranging from
176 to 851 mg/m3 (geometric mean of 309 mg/m3).
Results of post-exposure measurements of tear film stability and forced expiratory respiratory volume indicated
that short-term exposures to propylene glycol aerosol
can cause acute eye and upper respiratory irritation in
non-asthmatic patients.

ASHRAE Journal - June 2014

Table of Contents for the Digital Edition of ASHRAE Journal - June 2014