Ultrafine particles (UFPs) are particulate matter of nanoscale size (less than 0.1 μm or 100 nanometres in diameter). Regulations do not exist for this size class of ambient air pollution particles, which are far smaller than the regulated PM10 and PM2.5 particle classes and are believed to have several more aggressive health implications than those classes of larger particulates.
Contents
There are two main divisions that categorize types of UFPs. UFPs can either be carbon-based or metallic, and then can be further subdivided by their magnetic properties. Electron microscopy and special physical lab conditions allow scientists to observe UFP morphology. Airborne UFPs can be measured using a condensation particle counter, in which particles are mixed with alcohol vapor and then cooled allowing the vapor to condense around them which are then counted using a light scanner. UFPs are both manufactured and naturally occurring. UFPs are the main constituent of airborne particulate matter. Due to their numerous quantity and ability to penetrate deep within the lung, UFPs are a major concern for respiratory exposure and health.
Exposure, risk, and health effects
The main exposure to UFPs is through inhalation. Due to their size, UFPs are considered to be respirable particles. Contrary to the behaviour of inhaled PM10 and PM2.5, ultrafine particles are deposited in the lungs, where they have the ability to penetrate tissue and undergo interstitialization, or to be absorbed directly into the bloodstream — and therefore are not easily removed from the body and may have immediate effect. Exposure to UFPs, even if components are not very toxic, may cause oxidative stress, inflammatory mediator release, and could induce heart disease, lung disease, and other systemic effects. The exact mechanism through which UFP exposure leads to health effects remains to be elucidated, but effects on Blood pressure may play a role. It has recently been reported that UFP is associated with an increase in blood pressure in schoolchildren with the smallest particles inducing the largest effect.
There is a range of potential human exposures that include occupational, due to the direct manufacturing process or a byproduct from an industrial or office environment, as well as incidental, from contaminated outdoor air and other byproduct emissions. In order to quantify exposure and risk, both in vivo and in vitro studies of various UFP species are currently being done using a variety of animal models including mouse, rat, and fish. These studies aim to establish toxicological profiles necessary for risk assessment, risk management, and potential regulation and legislation.
Regulation and legislation
As the nanotechnology industry has grown, nanoparticles have brought UFPs more public and regulatory attention. UFP risk assessment research is still in the very early stages. There are continuing debates about whether to regulate UFPs and how to research and manage the health risks they may pose. As of March 19, 2008, the EPA does not yet regulate or research ultrafine particles, but has drafted a Nanomaterial Research Strategy, open for independent, external peer review beginning February 7, 2008 (Panel review on April 11, 2008). There is also debate about how the European Union (EU) should regulate UFPs.