Millions of buyers of ultrasonic humidifiers who thought they had finally found a safe and effective way to add moisture to their homes in the winter have something new to worry about.
Scientists at the Environmental Protection Agency have discovered that the ultrasonic machines can fill household air with tiny particles of minerals and pieces of microorganisms that can be inhaled deep into the lungs, where they may cause allergies or illness.
The potential hazard of ultrasonic humidifiers may come as a bit of a shock to those who bought the machines because they were whisper-quiet, energy-efficient moisturizers that, unlike cool-mist humidifiers, did not breed harmful microorganisms and spew them into the air.
The new finding explains a number of complaints from consumers who have reported that the use of an ultrasonic humidifier produced a chronic cough or allergic symptoms in one or more household members.
The problem is especially severe when consumers use mineral-laden tap water to fill their humidifiers and when the machines are not cleaned each day to keep bacteria and molds from accumulating. Particle levels in a closed bedroom could exceed the federal standard for particles in outdoor air by nearly 50 times, the study showed.
``Since humidifier use occurs primarily during periods when the occupants are present, long-term exposure to these increased levels may potentially result in either acute or chronic human health hazards,`` the researchers concluded in their report published in the September issue of Environmental Science & Technology, a journal of the American Chemical Society.
A BREEDING GROUND
Although the high-frequency sound waves of the ultrasonic units apparently kill microorganisms, the scientists said fragments of bacteria and molds can be spewed into the air; these may cause allergic symptoms in some people. In addition, if the indoor air is too humid, molds and other microorganisms may grow on household surfaces.
The scientists also warned that ``users should be aware of the potential respiratory irritations and health hazards that may result from the use or improper treatment of tap water`` in humidifiers.
The Association of Home Appliance Manufacturers said the EPA findings were ``preliminary and raised questions that call for additional research.``
Many people had assumed that ultrasonic machines solved the health risks associated with earlier types of humidifiers, which were linked to many cases of ``humidifier fever``-shortness of breath, cough, fever and malaise resulting from a reaction to microorganisms that can grow in the lukewarm or room-temperature water in the humidifier reservoir. But the newly discovered threat illustrates two problems.
One is a lack of standards and an enforcement agency to assure that consumer goods intended to prevent or correct health problems actually work as advertised. The other is the failure of many consumers to follow manufacturers` directions for safe and effective use of over-the-counter health-care devices.
IGNORING THE WARNINGS
While makers of ultrasonic humidifiers advise daily cleaning and most also recommend the use of filtered, demineralized or distilled water, the expense and inconvenience often prompts users to ignore these directions.
But even when the devices are filled with distilled water, the EPA researchers found that a large number of fine particles-twice the single-day standard-can fill the air.
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