It mentions a field study in Arizona that found significant mite
contamination in homes at RH as low as 40% RH (O"Rourke et al, 1993,
Indoor Air 93 Proc., 4: 155). This is also an interesting study because
it may refute assumptions in a recent comment on article on the
asthma/allegy epidemic and TB immunity (Cookson & Moffat, p. 41, re:
Shirakawa et al, 1997, Science 275: 77) that homes in Arizona do not
have dust mite problems (carpets on cold slab floors and
evaporative/swamp coolers do not seem to be a good idea for
asthmatic/allergic folks).
Arens and Baughman conclude that "rather than ambient RH, however, the
more relevant factor may be the RH within the microhabitat of the
mite". Seasonal/temporal variations appear to be important too, e.g.,
low humidity in the winter sufficient to kill of mite nymphs prevented
mite growth in humid summer season.
Re: low humidity, it mentions respiratory ailments in a paper by Green,
GH, 1985, AHSRRAE Trans. 91(1). You probably need to check the allergy
and respiratory disease literature, but info on low humidity is probably
even more limited than that on high humidity.
BTW, other newer papers worth reading are:
1) Michel et al., 1996 (AJ Crit.Care Resp.Med154:1641) suggesting that
dust mite allergen is contaminated with bacterial endotoxin that is a
triggering factor that increases severity of asthma.
2) David Miller & Christopher Young, 1997, AIHAJ 58(1): 39, re:
ergosterol as indicator of airborne fungi, from CMHC Wallaceburg moldy
home study.
3) Delfino et al., 1996, AJ Resp.Crit.Care.Med. 154: 633. which found
that asthmatic inhaler use was most associated (largest regression
coefficients) with fungi spores NOT included in the standard allergen
skin prick tests and not otherwise identified yet.
--
Thomas J. Phillips AIR {) FOOD
Air Pollution Research Specialist /|\
CARB/RD, Box 2815, Sacramento, CA 95812 WATER | SKIN
916.322.7145/4357 FAX, http://www.arb.ca.gov _/ \_
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