LOW FREQUENCY MAGNETIC FIELDS INSIDE CARS.

Magnetic fields were compared inside passenger seats of electric, petrol and hybrid cars. While driving about 5 km in an urban environment, values were recorded and compared between car types. The magnetic flux densities of the cars were less than 2.6 µT. The magnitudes of the magnetic fields of petrol cars and hybrid cars were about the same and slightly lower for electric cars. Based on our measurements, values were less than 3% of the guidelines given for the general population or people using pacemakers.

Ankle and exercise blood pressures as predictors of coronary morbidity and mortality in a prospective follow-up study.

Elevated ankle blood pressure (ABP) may be one of the earliest signs of subclinical atherosclerosis. However, its behavior in different degrees of atherosclerotic vascular damage has not been well characterized. We examined the association of ABP and brachial exercise blood pressure with the incidence of future coronary events. A cohort of 3808 consecutive ambulatory persons (mean age 50 years, 34% women), referred to a symptom-limited exercise test and free of cardiovascular events at baseline, was prospectively followed up for 15 years. Altogether, 383 (80 fatal and 303 non-fatal) incident coronary events occurred. Cox proportional hazards models, adjusting for several conventional risk factors, were used to analyse the independent association of ABP with the risk of an incident coronary heart disease (CHD) event. Persons with normal ankle, brachial resting and brachial exercise blood pressures were taken as the reference group. Other groups were formed on the basis of ankle and exercise blood pressures and compared with the reference group. Even in persons among whom the elevated ABP was the only abnormal finding, the multivariate adjusted hazard ratio (HR) of a future CHD event was significantly elevated (HR=1.60, 95% confidence interval 1.20-2.14, P<0.0001). In general, the HRs were higher for fatal events than for non-fatal events. The measurement of ABP could be an inexpensive and non-invasive tool to detect elevated risk of a CHD event.

Case fatality rates after first acute coronary syndrome in persons treated for type 2 diabetes show an improving trend.

AIMS/HYPOTHESIS: We analysed whether the prognosis of a first acute coronary syndrome (ACS) in patients treated for type 2 diabetes has improved. We also compared the trends in patients with and without diabetes. METHODS: We used national registers to identify all patients with clinically known type 2 diabetes in Finland during the years 1988 to 2002 (n = 222,940). All first-ever ACS events (n = 43,412) among these patients were identified using the Hospital Discharge Register and the Causes of Death Register. From the National Cardiovascular Disease Register we identified all first ACS attacks (n = 191,403) among non-diabetic patients in the country. Finally, we calculated annual age-standardised case fatality rates for ACS for three time periods: prehospital, days 0 to 27 and days 28 to 364 after the first ACS. RESULTS: The case fatality rate of first ACS declined significantly in both sexes at all time points considered. The declining trends were not different between patients with type 2 diabetes and those without. Among men aged 35 to 74 years, 58.5% (95% CI 57.6-59.4%) with type 2 diabetes and 44.1% (95% CI 43.8-44.5%) without diabetes had died from cardiovascular causes 1 year after their first ACS. Among women of the same age, the corresponding figures were 54.2% (95% CI 53.0-55.4%) and 36.5% (95% CI 35.9-37.1%). Men generally had higher case fatality rates than women. However, except for prehospital deaths, diabetic women had the same or even higher case fatality rates than non-diabetic men. CONCLUSIONS/INTERPRETATION: The case fatality rates for first ACS show similar improving trends in patients with type 2 diabetes and in those without. However, case fatality rates have remained higher in patients with type 2 diabetes.

Protection efficiency of hearing protectors against military noise from handheld weapons and vehicles.

Noise attenuation against military noises has been measured in several cases under practical field conditions. Commercial and military versions of earmuff noise attenuation were measured against rifle noise. All the tested earmuffs attenuated the C-weighted peak level to less than 135 dB, which is less than the proposed recommendation value. Combat and shooting exercises create a risk of hearing damage, reaching a peak level of 180 dB. Measurements were done during attack exercises with blank and normal cartridges and during a defence exercise with normal cartridges. The noise exposure levels were relatively moderate (outside the ear 95-97 dB, in ear canal 82-85 dB) for military exercises. Peak levels of 110-120 dB for military trainers were measured in the ear canal during the conscript use of small-bore weapons. Combat vehicles and tanks are noisy, and for noise control during their use headgear with communication properties is worn. Noise inside such headgear was found to reach up to 120 dB, and the noise doses varied between 90 and 105 dB. Noise was also measured for aviation pilots in Finnish jet fighters. The cockpit values averaged 96 dB - 100 dB over the flight, whereas noise in the ear canal averaged 88 dB - 95 dB. The analyses indicated that radio noise is 4-10 dB higher inside the helmet than the background noise is, when measured as equivalent noise. The technicians on the ground were exposed to noise levels varying from 93 to 97 dB over the day. In practice, hearing protectors attenuate noise by 10-30 dB, depending on the frequency content of the noise sources. However, the difference when measured outside and inside hearing protectors varies by 5-10 dB because communication increases the noise level at the entrance of ear the canal. Currently the best protection for soldiers seems to be active noise cancellation ear muffs that are equipped for communication purposes and worn during the entire military exercise.

A review of video exposure monitoring as an occupational hygiene tool.

This study reviews use of video exposure monitoring (VEM, also known as PIMEX) as an occupational hygiene tool since its inception in the mid-1980s. VEM involves the combination of real-time monitoring instruments, usually for gases/vapours and dust, with video of the worker's activities. VEM is an established method used by practitioners in different countries. The technical aspects of these VEM systems are described, then applications of VEM are discussed, focussing on task analysis, training (risk communication), encouraging worker participation in and motivation for improvements in the workplace environment and occupational hygiene research. The experiences from these applications are used to illustrate how exposure visualization with video can act as a catalyst, initiating a change process in the workplace. Finally, the role of VEM as a workplace improvement tool, now and in the future, is discussed.

Active noise reduction in aviation helmets during a military jet trainer test flight.

Cockpit noise measurements were carried out in a two-seat jet trainer. For the continuous time and frequency analyses a two-channel tape-recording system was constructed of two miniature microphones connected through an amplifier to a digital tape-recorder. The analysed and averaged noise exposure including radio communication was 80-81 dB when the ANC system was on and 84-89 dB when the ANC system was off. For the conventional flight helmet the same noise exposure was 86 dB, and the noise exposure in the cockpit was 104-106 dB. The effect of the ANC system on the averaged noise exposure (L(Aeq8min)) was an improvement of 4-8 dB over the noise attenuation of the same helmets when the ANC system was off. Both ANC systems worked properly during the test flights. No severe ringing or voice circulation was found except during extreme vibration.

Noise attenuation of hearing protectors against heavy weapon noise.

This study evaluated the noise attenuation of earplugs and earmuffs or their combined use against heavy weapon noise in field conditions for military personnel. The noise attenuation was measured with a miniature microphone inserted into the ear canal. The subjects (13) were tested against pink noise and against the noise of explosions and bazooka, mortar, cannon, and howitzer. The attenuation (insertion loss) was 16 to 23 dB for earplugs, 10 to 20 dB for earmuffs, and 24 to 34 dB for the combined use of plugs and muffs. The transfer function of an open ear was 5 to 7 dB when measured as the C-weighted peak level. The combined use of earplugs and earmuffs gave smaller attenuation values than expected. If the limit for the C-weighted peak level is 140 dB for unprotected ears, then protection against low-frequency noise is provided for up to 156 dB by earplugs, up to 150 dB by earmuffs, and up to 165 dB by the combined use of plugs and muffs.

Low-altitude overflights of fighters and the risk of hearing loss.

BACKGROUND AND OBJECTIVE: Much data are available on noise properties which cause hearing loss. There are not, however, reports on the effects of low-altitude overflight noise on the permanent threshold shift (PTS). METHODS: Low-altitude overflight noise generated by the Finnish Air Force's jet fighters and an advanced jet trainer was measured with flight distances varying from 50-310 m from the measurement point. The aircraft were always subsonic, velocities being usually 0.9 Mach or less. The measurements were undertaken because of two claims for the compensation of hearing loss caused by overflights of jet fighters on cross-country training missions. RESULTS: Peak noise levels (LCpeak) varied from 109-150 dB depending on aircraft type and the use of afterburner. The 1-s single A-weighted exposure levels (ASEL) during these overflights were 95-135 dB which correspond to daily (8 h) exposure levels of 50-90 dB. CONCLUSIONS: According to these results and the principles of noise evaluation, there should be no risk of permanent hearing loss when the distance to an overflying jet fighter is more than 200 m. However, we have received two claims, and the audiometric analyses of two subjects who had suffered hearing loss in one ear in Finland during the 1990s may indicate that there is very likely a connection between the incidents and the hearing losses.

Noise attenuation of communication hearing protectors against impulses from assault rifle.

The noise attenuation values of commercial and military versions of earmuffs were measured using a Finnish assault rifle (RK762) as the sound source. The C-weighted peak level at the entrance of the left ear of the shooter was 156 dB (SD 1.0 dB; n = 25 shots). The noise was analyzed both outside and inside ear muffs on military volunteers on an open shooting range. All the earmuffs attenuated the C-weighted peak level to a value of less than 135 dB, which is less than the proposed values recommended by hearing damage criteria. Communication hearing protectors seem to function and attenuate sufficiently against the peak levels of the impulse noises used in this study.

Physical characteristics of gunfire impulse noise and its attenuation by hearing protectors.

The peak sound pressure level (SPL), spreading of pressure wave and other physical characteristics of the impulse noise from weapons were studied in actual shooting conditions for assessment of gunfire noise exposure. Additionally, the attenuation of SPL by hearing protectors was measured with miniature microphones to evaluate protection efficiency in real shooting conditions. The peak SPLs at the shooter's ear ranged from 132 dB (miniature rifle) to 183 dB (howitzer). The spectral content of the main part of the acoustic energy was less than 400 Hz (peak 16-100 Hz) for large-caliber weapons and 150-2,500 Hz (peak 900-1,500 Hz) for small-caliber weapons (rifles). The safe distances from the noise source (less than 140 dB peak SPL) were 50-200 m for large-caliber weapons. Rifle impulses (assault rifle, caliber 7.62) had a peak SPL of 154 dB at a distance of 4 m from the muzzle. The peak SPLs of different explosives ranged from 125 to 185 dB at distances of 10 to 300 m. In rifle shooting, the attenuation efficiency of earplugs (16dB) or small-volume (thin) earmuffs (17 dB) was not sufficient and their use as sole protectors cannot be recommended. Instead, large-volume earmuffs should be used. Impulses from pistol and shotgun were fairly effectively attenuated both by small-volume and large-volume earmuffs. All kinds of earmuffs appeared to be ineffective (attenuation less than 15 dB) against impulses from large-caliber weapons with energy content at very low frequencies. Therefore, the combined use of earmuffs and earplugs is recommended for the most noisy operations. On the basis of the present data, wider safety zones were adopted in the Finish Defence Forces at shooting with different weapons.

Development of a new noise helmet.

A prototype for a new noise helmet was developed because high noise levels were not sufficiently attenuated by commercially available helmets. The new helmet was designed to be tight, especially in the area of the throat and face, and to cover the entire head. The noise attenuation properties of the new helmet were tested against pink noise in an anechoic room, jet engine noise, and low-frequency noise with the test subjects wearing a miniature microphone under the protector. The new helmet provides insertion loss of over 50 dB, which is 18-29 dB more attenuation than that of the tested earmuffs in the frequency range of 1-8 kHz. It is also better (8-13 dB) than the tested earmuffs at frequencies of 125-1000 Hz, and it protects against air impurities because the air fed into the helmet is filtered.

Attenuation of low-frequency noise by hearing protectors.

The ability of earmuffs and helmets to reduce low-frequency (4-250 Hz) noise was tested in an anechoic chamber, in a paint factory, outside and in a low-frequency noise chamber. Prototypes of a new noise helmet were also tested. Steady noise and low-frequency noise impulses were used as the sound sources. The testing was sometimes difficult because physiological noise raised the sound level inside the hearing protector at some frequencies after the protector was put on. Therefore the low-frequency sound level had to be over 100 dB at frequencies of 2-250 Hz during the tests. The earmuffs attenuated noise levels of 1-20 dB in the 4-250 Hz frequency range. Commercial noise helmets tested were not as good as earmuffs in attenuating low-frequency noise. New noise helmet prototypes attenuated low-frequency noise better than did earmuffs or commercial helmets (attenuation 5-39 dB).

A study on the mutagenic activity of styrene and styrene oxide.

Styrene oxide is multagenic, without metabolic activation, to S. typhimurium strains TA 1535 and TA 100, which have been devised to detect mutagens causing base-pair substitutions. Styrene seems to be mutagenic toward the same strains, but only after metabolic activation. The toxicity of both styrene and styrene oxide make the construction of reliable dose-response curves rather difficult. Diethylmaleate and 3,3,3-trichloropropene oxide enhanced the mutagenicity of styrene oxide in the presence of homogenate; this result indicates the participation of epoxide hydratase and glutathione S-oxide transferase in the metabolism of styrene oxide. These two chemicals did not influence the mutagenic activity of styrene. Styrene glycol and 4-tert-butyl-brenzcatechin were not mutagenic to any of the strains studied. Results show that further, more detailed experimental and, possibly, epidemiologic studies are warranted.