History of Ozone in Timeline
Ozone (O3) is a pale blue gas with a pungent smell. This allotrope of oxygen is less stable than the diatomic oxygen (O2) found in the lower atmosphere. Ozone forms in the Earth's atmosphere from the reaction of dioxygen (O2) with ultraviolet (UV) light or electrical discharges. Although found in low concentrations throughout the atmosphere, its highest concentration is in the stratospheric ozone layer, where it absorbs most of the Sun's UV radiation.
1908: Ozone Disinfection Introduced in London Underground
In 1908, the Central Line of the London Underground implemented artificial ozonisation as a method for aerial disinfection.
1910: OSHA Establishes Ozone Exposure Limits for Worker Safety
In 1910, recognizing the potential hazards of ozone exposure, the U.S. Occupational Safety and Health Administration (OSHA) set a permissible exposure limit (PEL) of 0.1 µmol/mol, calculated as an 8-hour time-weighted average.
1911: Harmful Effects of Ozone Documented
In 1911, Leonard Hill and Martin Flack challenged the belief that ozone was healthful, highlighting the lack of scientific evidence for these claims. Their research, published in the Proceedings of the Royal Society B, underscored ozone's harmful effects, particularly its irritation and potential harm to the lungs.
1923: Oxozone Hypothesis Disproved
In 1923, Georg-Maria Schwab, during his doctoral research under Ernst Hermann Riesenfeld, achieved a breakthrough by successfully solidifying ozone. This allowed for accurate analysis, ultimately disproving the long-standing oxozone hypothesis.
1955: Study Period Begins for Ozone Impact on Upper Southern Ocean Warming
A study period commenced in 1955 to investigate the role of ozone in climate change.
1956: Ozone Disinfection Phased Out in London Underground
By 1956, the intentional use of ozone for disinfection in the London Underground was phased out, although the electrical discharges from train motors continued to produce ozone incidentally.
1987: Montreal Protocol Addresses Ozone Depletion
Growing concerns about the depletion of stratospheric ozone due to substances like chlorofluorocarbons (CFCs) culminated in the signing of the Montreal Protocol in 1987. This international treaty aimed to phase out the production of ozone-depleting substances, marking a significant milestone in environmental protection.
1997: EPA Establishes 8-Hour Ozone Standard
In 1997, the EPA set a new standard for ozone levels, aiming to reduce the harmful effects of ground-level ozone on human health and the environment.
2000: Study Concludes Ozone Increase Contributes to Southern Ocean Warming
By 2000, research revealed that the increase in tropospheric ozone was a significant factor in the warming of the upper Southern Ocean interior between 1955 and 2000, highlighting ozone's role in regional climate change.
2003: Study Highlights Combined Effects of Ozone and Heat on Mortality
A study conducted in 2003 revealed a concerning link between ozone levels, heat waves, and mortality rates in Europe. The investigation concluded that the combination of high ozone concentrations and extreme heat had additive effects on mortality.
2004: EPA Designates Denver Area as Non-Attainment for Ozone
The EPA designated the Denver Metro/North Front Range area as non-attainment for the 1997 8-hour ozone standard in 2004 due to high ozone levels, highlighting the region's struggle with air quality. This designation underscored the need for comprehensive measures to reduce ozone and improve air quality.
2007: Denver's Non-Attainment Status for Ozone Takes Effect
Denver's non-attainment status, designated in 2004, came into effect in 2007, triggering the implementation of the Colorado Ozone Action Plan. This plan outlined strategies to curb ozone levels and bring the region into compliance with EPA standards.
May 2008: EPA Lowers Ozone Standard
In May 2008, the EPA lowered the ozone standard from 80 nmol/mol to 75 nmol/mol, a move that sparked debate despite being driven by health concerns related to ground-level ozone.
2008: EU Directive Addresses Ozone Pollution
Directive 2008/50/EC, adopted by the European Union, set air quality standards for ozone pollution to address its impact on human health and the environment. This directive aimed to improve air quality across EU member states.
2008: EPA Proposes Lower Ozone Standard for Health Protection
In 2008, the EPA took further action on ozone levels, pushing for a reduction in the 8-hour primary standard. This proposal, part of the final rule, aimed to set the standard within the range of 0.060 to 0.070 μmol/mol. The goal was to enhance protection for vulnerable populations, especially children, from a range of adverse health effects linked to ozone.
2008: Colorado Implements Ozone Action Plan
In response to its non-attainment status for ozone, Colorado developed the Colorado Ozone Action Plan in 2008 to mitigate ozone pollution. The plan included measures to evaluate and control emissions from various sources.
January 7, 2010: EPA Proposes Revisions to Ozone Standards
On January 7, 2010, the U.S. Environmental Protection Agency announced its intention to further revise the National Ambient Air Quality Standard (NAAQS) for ozone, aiming to reduce the allowable levels of this pollutant in the atmosphere.
January 2010: EU Sets Ozone Concentration Target
Starting in January 2010, the European Union implemented a target value for ozone concentrations, aiming to limit it to 120 μg/m, which is approximately 60 nmol/mol, to protect public health and the environment. This target applied to all member states as part of Directive 2008/50/EC.
2011: Regional Haze Plan Targets NOx Emissions
Colorado's Regional Haze Plan, launched in 2011, included a detailed plan to decrease nitrogen oxide (NOx) emissions. NOx emissions contribute to ozone formation, and this plan aimed to improve visibility and overall air quality in the region.
October 26, 2015: EPA Publishes Final Rule for Revised Ozone Standard
The EPA officially published a final rule on October 26, 2015, solidifying the revision of the 8-hour primary National Ambient Air Quality Standard (NAAQS) for ozone. This revision lowered the standard from 0.075 ppm to 0.070 ppm.
December 28, 2015: Revised Ozone Standard Takes Effect
Following its publication in October, the EPA's revised ozone standard went into effect on December 28, 2015, marking an important step in addressing ozone pollution.
2021: Ozone Generators Deployed in Wales Schools for COVID-19 Disinfection
During the Autumn term in 2021, ozone generators were distributed to schools and universities across Wales to disinfect classrooms following COVID-19 outbreaks.
2022: Study on Economic Impact of Ozone Pollution in East Asia
In 2022, a study revealed that ozone pollution, a byproduct of fossil fuel combustion, leads to significant crop losses in East Asia, costing an estimated 63 billion dollars annually. China, in particular, experiences substantial losses, with one-third of its potential wheat production and one-fourth of its rice production affected.