Laboratory and Epidemiology Communications

Air quality Monitoring in a Neonatal Intensive Care Unit
Kiminori Toyooka, Hirofumi Miyazawa, Yoshikazu Naiki, Yumiko Ishii,Fumiko Nishiyama, Tadatoshi KuratsuJl and Teruo Kirikae*International Medical Center ofJapan,
Toyama 1‑21‑1, Shinjuku‑ku, Too,0 162‑8655
Communicated by Hiroshi Yoshikura(Accepted May 31, 2001)
Air sampling in health care facilities, especially in special‑care areas such as neonatal intensiv? care units (NICUs),
should be done on a periodic basis ln Order to determine
indoor air quality, efficacy of dust control measures, or air‑handling system performance. (The draft guideline is avail‑able with the full text of this article at http://www.cdc.gov/ncidod/hip/enviro/env̲guide̲draft.pdf) ( 1 ). A practicalmethod to assess Fir qualityis to monitor airborne particles
with in a certaln Size range using particle counters (2).

Airbome particles and wind speed were continuously
monitored in an NICU with five beds from 0:00 to 18:00 0n
weekdays. The NICU was 199.6 m3 in size (76.75 m2floor
space by 2.6 m high), and equipped with an anteroom of21. 1m3 (8.1 m2floor space by 2.6 m high) and a fixed dustedroom‑air recirculation system with 85.4 % retum. As shownin a sketch of the NICU (Fig. I), four air‑supply vents werelocated in the ceiling and fittedwith high‑efficiency particulateair (HEPA) filters for air cleaning･ Two air‑exhaust vents werelocated near the floor ln two comers and three were locatedFig. 1. Sketch of an NICU

in the ceiling. The volume of air supply was 4,800 m3/h, andthe air changed 24 times per hour. In the room were sevenincubators,including two spares,and five monitonng equlPment
units, respirators, a radiant warmer, several shelves forsolutions, medical supplies, records, and other materials. Air‑cUJSOPFUedbome particles of ≧1.0 LLm diameter and wind speed werecontinuously monitored using a laser particle counter (KC‑
03Al, 及ion Co., Tbkyo) and a wind meter (6521, Kanomax

Co･, Tokyo) placed at different places in the room (point A,B, or C indicated in Fig. 1) 1 m above the noor. PointAwas
under an air‑supply vent in the center of the room, polnt 良

was near an air‑exhaust vent in a corner, and point C wasnear an air‑exhaust vent in the ceiling and su汀Ounded by anincubator, a monitorlng equlpment unit, and a sink unit.

The mICtuation in airbome particles in the NICU is shown

0:00

3:00

6:00

9:00

12:00

15:00

18:00

Timein Fig･ 2. At point A, the particle number was 10 ‑ 80/ft3 (4 ‑30 X 102/m3) which was the lowest levelamong the three moni‑Fig. 2. Monitonng ofairbornc particles in an NICU. Airborne particlesof>1 ･O Elm diameter wcrc counted (averaged over 1 min periods)*Co汀eSpOnding author: Fax: +8 1‑3‑3202‑7364, E‑mail: tkirikae

from 0:00 to 1 8:00, Each plot represents the average particle counts atintervals at pointA, B, and C.

@ri.imcj.go.jp

87(Accepted June 1, 2001)

On 28 October 2000, Chiba Prefecture experienced a mass
infection of enterohemorrhagic Escherichia colt (EHEC)
0157 at a live‑stock festival. There were 58 infected cases,tion conducted on the same day revealed that all the patients

30 0f which exhibited symptoms.

Aspossibilities other than the roast as a c?use remained, pulsed

EHEC 0 1 57 case to Funabashi Health Center. The investlga‑
had ingested the whole roasted cow provided at the festival.

The causative agent EHEC 0157 was traced to the whole

丘eld gel electrophoresis (PFGE) analysts Of the isolates wasroasted cow which was served to several hundred of theperfわrmed immediately. At the same time, Funabashi Cityparticipants.Asthe incident relates to both food poISOnlng

opened a consultation station to the general public which

and infectious disease which are under different regulatory

side.Asthe festival provided unrestricted accessibility andprovided examination of stool specimens on request. On 1 3
November, five specimens including the above three were
found to have identical PFGE pattems, and all of the reported

schemes in Japan, there was some diWICultyon the regulatory

several hundred people participated, it was difncult to identify

ten patients including the above three were found to have

who ingested the roast. The possibility of unnoticed cases

lngeSted the roast. The culprit fわod was detemined on theand secondary spread of the infection remained throughout

same day to be the whole roasted cow. MicrobiologlCal

the investlgation which lasted until December 22.

investlgation of the commercial route of the meat and thatremainlng at the festival was unable to isolate EHEC O157,
however. The PFGE pattem or the isolates was one which
had not been rep.orted before (information from National
Institute of lnfectlOuS Diseases).

The incident came to the notice of the regulatory authority

on November 8･ On that day, three different clinics reported an*Co汀eSpOnding author: Present address: Public Health Promo‑

The whole roasted cow that caused the incident wastion, Chiba Prefecture, Ichibacho I ‑ 1 , Chuo‑ku, Chiba 26018667,

E‑mail: t.nmr5@ml.pref.chiba.jp

prepared in the fbllowlng Way. A halfofa cow whose viscera88