ASHRAE Journal - June 2022 - 18

TECHNICAL FEATURE
TABLE 2 Human body effects of EPA regulated pollutants.
POLLUTANT
Particulates
Ozone
Nitrogen dioxide
SYMPTOMS
Asthma,
lung inflammation, decreased
lung function, irregular
heartbeat
Asthma,
breathing difficulties,
lung inflammation
Eye, irritation,
respiratory irritation, fatigue
Carbon monoxide Dizziness, headache, nausea,
shortness of breath, chest
pain
Lead High blood pressure, joint and
muscle pain, headache,
difficulties with memory or
concentration
Sulfur dioxide
Breathing difficulties, chest
tightness
Cardiovascular
Skeletal system,
nervous system,
kidneys, immune
system, cardiovascular,
reproductive
system
Respiratory tract, eyes
Data primarily derived from https://www.epa.gov/criteria-airpollutants
Tabulation
of symptoms, health effects, and target organs is
representative, and not inclusive.
performance-based standard (RESET) specifies a CO2
limit of 600 ppm for " high-performance " ventilation.17
The prevalence of sick building syndrome symptoms
(eye/throat/nose irritation, breathing difficulty, headache,
nausea and dizziness, and mental fatigue) is often
associated with poor air quality.16
A statistical analysis18 of data from the EPA's Building
Assessment Survey and Evaluation study, which collected
air quality data from 100 office buildings throughout
the United States over a five-year period,19 found
a significant correlation between indoor CO2 levels
relative to outdoor CO2 levels and some sick building
syndrome symptoms. The results suggest that increasing
ventilation rates, and thus reducing indoor CO2 levels,
will also significantly reduce the prevalence of certain
sick building syndrome symptoms, even in buildings
with initial CO2 levels at or below 1,000 ppm.18
Table 2 presents a tabulation of nominal health effects
from the six outdoor pollutants regulated by the EPA.
The effects appear to be fairly similar to the symptoms
associated with sick building syndrome.
Correlations between outdoor CO2 levels and some
outdoor pollutant concentrations have been made in a
few urban areas,11,20,21 but while CO2 serves as a good
indicator of the presence of airborne pollutants, the
18
ASHRAE JOURNAL ashrae.org J U N E 2022
Lungs
TARGET ORGANS
Respiratory tract,
cardiovascular (heart)
Respiratory tract
linear relationships are highly dependent on locality
and time.20 Additionally, municipalities monitor the
six pollutants defined by the EPA, but do not monitor
concurrent CO2 levels. Also, nationwide average EPAregulated
pollutant levels have been dropping in the
United States,4 while world CO2 levels have been consistently
going up.8 The ratio between airborne pollutants
and CO2 thus clearly changes over time. Adding CO2 to
the data collection would help researchers to understand
better what relationships and trends may exist
over time and in different localities. Such knowledge
could be valuable in optimizing demand-controlled
ventilation systems22 and any ventilation system where
outdoor air is brought in.
One study21 finds correlation between indoor and outdoor
CO2 levels as well as between corresponding indoor
and outdoor particulate concentrations in urban homes.
Basically, as outdoor pollution goes up, so does indoor
pollution.
Studies focusing on CO2 impacts on biological organisms
and their respective pathogenicities find that higher
CO2 levels generally enhance plant growth. It has been
shown that CO2 stimulates earlier and greater allergenic
pollen production.23 Bacterial and fungal reactions to
CO2 vary depending on whether they make or consume
CO2 in their metabolism. Alternaria alternata and Aspergillus
fumigatus are two asthma-inducing fungi commonly
found indoors as well as outdoors.24,25 Studies have demonstrated
that elevating CO2 concentrations from present
outdoor levels to around 500 ppm significantly increases
the allergenicity of these two species.26,27
It is expected that the rise in CO2 and the resulting
climate change will cause changes in biological activity,
which will in turn increase asthma and allergies.25
However, it is noted that humidity and hygiene are considered
to be greater contributing factors to bacterial
and fungal activity than CO2. While many fungi found
indoors give off CO2 along with their characteristic
MVOCs, this author found no studies that positively correlate
fungal/bacterial activity with building space CO2
levels. One study investigating the matter was unable to
find a significant relationship.28
Summarizing the preceding discussion, studies suggest
that (1) outdoor pollutants exist in rough proportion
to respective outdoor CO2 levels, (2) indoor pollutants
giving rise to certain sick building syndrome symptoms
exist in some proportion to indoor CO2 levels, (3) indoor
https://www.epa.gov/criteria-air-pollutants https://www.epa.gov/criteria-air-pollutants http://ashrae.org http://www.ashrae.org
ASHRAE Journal - June 2022

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