¿ìè¶ÌÊÓƵ

IN LOS ANGELES, the land of the automobile, officials plan to ban the
‘drive-up’ bank teller and the ‘drive-thru’ McDonald’s. This measure, designed
to keep cars from idling unnecessarily, is one of the most obvious signs
that Los Angeles, like many other American cities, is serious about combating
air pollution.

Across the US, there seems for the first time in 20 years to be a political
will to comply with the provisions of the Clean Air Act of 1970. With this
act, the US set high standards for air quality, but it never described exactly
how the standards were to be met nor did it regularly punish offenders.
As a result, the costliest and most difficult pollutant to control, ozone,
remains at dangerously high levels of concentration in the air. Congress
is now amending and strengthening the law, after trying and failing to do
so every year of the past decade.

The difference this year is that many industrialists, fearful of even
tougher legislation and mindful of President Bush’s commitment to protect
the environment, broadly support the proposed changes to the Clean Air Act.
While they object to specific proposals as too costly, they are not spending
large amounts of money on campaigns to block all amendments, as they did
in the 1980s.

The Clean Air Act of 1970 divides the country into 242 districts and
sets limits for six key pollutants: lead, nitrogen oxides, sulphur oxides,
particulates, carbon monoxide and ozone. Nearly every district meets the
standards for the first four, but almost 100 cities still exceed those for
carbon monoxide and ozone. About 86 per cent of carbon monoxide in cities
is produced by automobiles. Emissions will drop progressively as more people
buy newer automobiles with cleaner engines (‘The exhausting options of modern
vehicles’, ¿ìè¶ÌÊÓƵ, 13 May 1989). Controlling ozone is more complicated.

Ozone is a highly reactive molecule made of three atoms of oxygen. In
the upper atmosphere ozone is useful for blocking harmful solar rays, but
on the ground it destroys molecules important to many biological processes.
Ozone weakens the body’s immune system and attacks lung tissue: according
to the US Centers for Disease Control, ozone destroys lung tissue almost
as well as some chemical weapons do.

In 1970, when the unhealthy effects of ozone were thought to begin at
a concentration of 0.25 parts per million, the Clean Air Act set the ‘safe’
level at 0.12 ppm. According to the Office of Technology Assessment, in
a study for Congress published in July last year, most air pollution specialists
now think that spending a day breathing air with an ozone level of 0.14
ppm will harm active people, such as construction workers or playing children.
Some of them think that a level of 0.8 ppm all day is harmful, the OTA study
adds.

Ozone is formed when ultraviolet light breaks down nitrogen dioxide
into nitrogen oxide and atomic oxygen, which are both very reactive. The
oxygen atoms combine with oxygen molecules, or dioxygen, in the air to make
ozone. Ozone will not accumulate when it can react rapidly with the nitrogen
oxide to reform nitrogen dioxide and dioxygen. The trouble occurs when organic
gases are present. The oxygen atoms in these gases, which are mostly hydrocarbons,
allow nitrogen oxide to form nitrogen dioxide without the intervention of
ozone. This dispenses with the chemical path that breaks down ozone, allowing
the gas to accumulate.

Vehicles produce almost half the hydrocarbons in the air: cleaner engines
should help to reduce these emissions. More difficult to control are the
organic chemicals that evaporate from hundreds of other different sources,
ranging from large factories to home cleaning fluids. Industry has two options:
it can either clean the air after the air has absorbed the hydrocarbons,
or it can redesign its products and processes so that they emit fewer hydrocarbons.

Filters, flames or new equipment

Traditionally, industry controls pollution by cleaning the air blowing
through its manufacturing equipment with an extra piece of machinery fitted
on the end of the production line: its favourite device is a porous charcoal
filter. Weak electrostatic forces attract the molecules of the organic gases
to those in the charcoal; sometimes there is chemical bonding between the
two. Industry adapted the technique from a process it developed to recover
expensive chemicals from waste products: it steam-cleaned the filters and
separated the chemicals from the condensed steam. While the method is useful
for recovering small amounts of chemicals, manufacturers have found that
it is an inefficient way of cleaning large volumes of air; decontaminating
thousands of cubic metres of air per minute quickly saturates the filters.

As an alternative, industry often resorts to burning off the hydrocarbons
in the waste stream, but this method is far from satisfactory. The process
produces dinitrogen oxide, carbon monoxide and incompletely burned hydrocarbons,
and manufacturers must frequently add natural gas to the waste stream to
fuel combustion.

The shortcomings of traditional methods have encouraged industry to
devise new ways of cleaning the air that it discharges into the atmosphere.
Last year, General Dynamics, the huge aerospace company based in St Louis,
Missouri, bought the first industrial machine that uses ozone to remove
hydrocarbons from the waste stream. It installed the equipment at its factory
in southern California. The company says that it controls the level of ozone
carefully to ensure that all the gas is used in the reaction and does not
leak from its factory. Although carbon dioxide, a ‘greenhouse’ gas, is a
byproduct of the cleaning process, the company considers this pollutant
to be of less immediate concern than the toxic ozone that hydrocarbons help
to accumulate.

The new machine cleans air in three stages. Intense ultraviolet light
breaks down the organic molecules as the air streams into the machine from
the factory. A fan then blows these fragmented molecules over water and
up through a water mist. The water is saturated with highly reactive oxygen
molecules in the form of ozone, peroxides and single oxygen atoms. General
Dynamics says that these reactants convert nearly all the organic gases
into carbon dioxide and water. Ozone-saturated water also cleans the carbon
filters that the company uses to remove any remaining traces of hydrocarbons.
According to Terra Aqua, the Californian company that makes the purifier
for General Dynamics, the state’s pollution inspectors have found the factory’s
exhaust fumes to be cleaner than the air outside the factory.

Other companies feel they have done all they can to reduce the level
of hydrocarbons in the exhaust fumes from their factories. Chemical giants
such as Monsanto, based in St Louis, and Du Pont, based in Wilmington, Delaware,
are now looking for ways of cleaning up their manufacturing processes. They
have found that simple adjustments to processes that have been standard
for decades can lower emissions of volatile chemicals and increase yields.
For instance, by changing the temperatures and pressures in a reaction to
produce adipic acid, a chemical used in the manufacture of nylon, Du Pont
halved emissions of cyclohexane, propane and butane and increased yield
by up to 1 per cent.

Last year, Monsanto promised to reduce the chemical emissions from its
factories by 90 per cent. Although no timescale was specified, the company’s
engineers are examining every one of Monsanto’s manufacturing processes
in an effort to meet the commitment. One of the first innovations concerned
the production of mothballs. Monsanto changed the solvent it uses from perchloroethylene
to isopropyl biphenyl, which is one-tenth as volatile.

Industry is also looking at ways of making its products less polluting.
Much research is focused on paints and other coatings, which contain volatile
hydrocarbons and are among the most polluting products on sale. These emissions
are also difficult to control. In the US, the total volume of hydrocarbons
released as these coatings dry, on cars, walls, furniture and paper for
instance, is even more than that emitted by the country’s entire chemical
industry. According to California’s South Coast Air Quality Management District,
which monitors air quality in the Los Angeles basin, drying veneers in a
large city release more than 130 tons of organic gases every day. Drying
adhesives release one-tenth as much again.

Paints usually comprise a ‘binder’ that forms a durable coating, an
‘extender’ to make the coating flow so that it is easy to apply and pigments
that give the coating colour. Most of the extender, which is either water
or an organic solvent, evaporates as a coating dries. Many binders are volatile
pollutants but it is the organic solvents that emit by far the most hydrocarbons.
Paints used in the home tend to use water as the extender, which does not
contaminate the atmosphere when it evaporates. Industry prefers to use coatings
with organic solvents, which it says look better and last longer. Companies
also say that organic solvents allow coatings to be applied over a broader
range of temperatures – an important asset for painting contractors, for
instance, redecorating buildings on the outside in all weathers.

One way of reducing paint’s polluting emissions is to use less of it.
Spray painting is much more efficient when the paint droplets are charged
with static electricity, something that has been known for many years but
not widely used. Coatings that use organic solvents are nonconductive and
can be charged from an electrode in the middle of the paint spray nozzle.
Although an electrical potential of around 80,000 volts is necessary, the
object being painted has only to be earthed to attract a thin coating. The
technique can reduce the volume of evaporating solvent by between 30 and
80 per cent, say officials from California’s South Coast Air Quality Management
District. The state intends to make electrostatic painting mandatory for
all processes that can use the technique.

Alternatively, industry can dispense with solvents altogether. One method
is to apply coatings as powders that melt to a smooth finish when heated
to between 250 to 300 Degree C. Only 5 per cent of industrial painting is
done this way though the number of applications of the technique is growing
in the US at between 10 and 20 per cent per year, says John Graham, director
of the Coatings Research Institute of Eastern Michigan University. One problem
is that the object being coated must be able to withstand the high temperatures.
The car industry, meanwhile, is investigating another method. General Motors
is trying to vacuum seal its vehicles in a plastic film that it can then
melt permanently into place. The technique will not be ready for the production
lines for about three years.

Chemists have begun to look to nature for help to produce solvent-free
paints. In their search for a binder that flows easily and thus dispenses
with the need for a solvent, scientists at the Coatings Research Institute
discovered oil from the seed of an African plant, Vernonia galamensis. Synthetic
binders that flow easily exist but they are expensive to produce. Vernonia
oil is cheap and it is chemically similar to linseed oil, which has been
used as a binder in paints since the Middle Ages. However, unlike linseed
oil, which is viscous at 10 Degree C, Vernonia oil flows easily even at
temperatures below 0 Degree C. Using Vernonia oil, paints need only half
the usual amount of volatile solvents and they harden quicker, say scientists
at the institute – although they cannot yet say why.

Public health officials in Los Angeles have learnt that reducing industrial
emissions alone is not enough to cut ozone levels in the city significantly.
The city’s problems are so great – on particularly sunny days, the concentration
of ozone soars above 0.36 ppm, three times the legal limit – that officials
intend to regulate nearly every source of volatile hydrocarbons. For instance,
antiperspirant sprays release 3.4 tons of the pollutant into the city’s
air every day and the state has already enacted legislation to phase them
out. This may not seem much considering that Los Angelenos emit a total
of about 700 tons of hydrocarbons daily, but every little counts when officials
estimate that emissions will need to be cut by 82 per cent if the city is
to meet the promised provisions of a more stringent Clean Air Act. Next
year, the city plans to ban the volatile fuel used to ignite barbecues;
this ‘starter-fluid’ can add up to 2 tons of hydrocarbons to the atmosphere
a day. Bakers will also have to control the 5.8 tons of ethanol that their
yeast produces daily, and farmers will need to think more carefully about
how they dispose of their cow manure, which releases 37.8 tons of methane,
ethane and ammonia every day. And from 1992, suburbanites will be prohibited
from cutting their lawns with petrol-driven mowers.

The Air Quality Management Plan for Los Angeles contains 120 such rules,
which the city hopes will bring the air up to federal standards within 20
years. Implementing the measures will cost between $600 and $2200 per home
every year, but savings in health care will be greater with cleaner air,
say city officials. According to William Fay of the Clean Air Working Group,
a lobby group based in Washington, LA’s success in beating air pollution
is being watched nationwide. ¿ìè¶ÌÊÓƵs and industrialists say the city
will serve as a laboratory for improvements in technology to control ozone.

* * *

Japanese industry shuns rules to control its emissions

A COMMON image of Japan around the world is of a country where people
wear smog masks in city streets and dive into department stores to breathe
pure oxygen from coin-operated machines. Japanese city-dwellers certainly
do these things, but not because their air is particularly polluted. The
masks are there to stop colds spreading, while pure oxygen is a trendy cure
for hangovers.

But Japan has no reason to be complacent about pollution even though
levels of contaminants in the air are below those in other industrialised
nations. According to the country’s Environment Agency, established in 1971
to eliminate pollution, the quality of air in Japan has stopped improving.
After falling since the early 1970s, concentrations of atmospheric pollutants
have started to level off; some are even going up.

The average concentration of nitrogen oxides was 0.042 parts per million
in 1988, the second-worst level since surveys began in 1971. This was an
increase from 0.036 ppm in 1985. The average concentration of carbon monoxide
fell from 6 ppm in 1972 to 2.4 ppm in 1984, but it has remained steady since,
the Environment Agency says. The concentration of sulphur dioxide peaked
at 0.059 ppm in 1967, falling to 0.010 ppm two decades later. Levels have
not fallen appreciably since.

Japan’s strict laws to control pollution from motor vehicles date from
1966. Catalytic converters have been compulsory since 1973. These reduced
by 90 per cent the amount of nitrogen oxides that cars could emit. Since
then, the number of cars on Japan’s roads has climbed steadily, as has the
average size of engine. People are also using their cars more; car journeys
accounted for 44.8 per cent of passenger-kilometres in Japan in 1985, compared
with 30.9 per cent in 1970. The gain was at the expense of buses and trains.

Outputs of some industrial pollutants, in particular carbon dioxide
and volatile hydrocarbons, dipped after 1985 when the rise in the value
of the yen made heavy industry uncompetitive in Japan. But the continuing
economic boom meant that the effect was only a temporary one, however.

Laws to enforce clean air came late to Japan and national standards
of environmental quality covering air, water and noise pollution are merely
guidelines. Furthermore, the decisions of the Environment Agency carry little
weight compared with those of other government bodies, such as the Ministry
of International Trade and Industry and the Construction Ministry, which
are responsible for promoting industrial expansion.

Japan is still paying the price for earlier laxness during the days
of rapid industrial growth. The government admits that 150,000 people qualify
for aid under a 1973 law that promises compensation for victims of diseases
caused by air pollution. Organisations representing sufferers say the total
is much larger. The heaviest tolls are in the industrial cities of Kawasaki
– where more than 1000 people qualifying for compensation have died – and
Osaka.

Japanese industry fights tighter controls on pollution, pointing out
its factories already use energy much more efficiently than their foreign
competitors. According to government figures, the US would consume 1.86
times the amount of energy to produce the same gross national product as
Japan, while West Germany would consume 1.46 times as much.

This conservationist ethic did not grow out of concern for the environment
so much as out of fears of Japan’s vulnerability to fluctuating trading
conditions. Japan has to import all its fossil fuels, so for decades keeping
consumption low has been a priority for both government and industry.