In my last blog, I presented the idea that consumerism was a major driver of chemical innovation and that the development of synthetic chemicals during the industrial revolution saw us sleepwalk into chemical dependency. In this blog, I use roads as a seemingly benign product that exemplifies societal dependence on synthetic chemicals. The change in the chemicals and substances used to construct roads is also used to show how consumerism leads to the development of yet more chemicals in a continual cycle of chemical innovation and replacement.
Wix stock image: Truck of logs
Modern roads are engineering marvels that have relied on the production and supply of two primary synthetic substances: asphalt and tar. Asphalt is a complex mixture of synthetic hydrocarbons refined from the non-volatile components of crude oil. Tar (commonly referred to as coal tar), on the other hand, is a by-product of coke and gas production from coal that is chemically different from and far more toxic than asphalt. Other substances are also added to roading mixes to maximise their performance, including polymer (e.g., styrene butadiene), anti-strip (e.g., polyamines), filler (e.g., fly-ash), and miscellaneous (e.g., naptha) substances.
Developed in the early 1900s, both asphalt and tar sealed roads rapidly replaced their dirt-road predecessors, due to their superior ability to transport vehicles and presumably pedestrians. The discovery of environmental hazards led to tar being phased out of use in the mid-2000s in many jurisdictions. However, asphalt remains globally ubiquitous in almost every human settlement with its presence dependent on the supply and development of synthetic chemicals made from hydrocarbons.
The industrial revolution that saw development of asphalt and tar also saw the development of motorised transport, the pneumatic (i.e., air-containing) tyre, and ensured further production of bituminous roads. First developed by Karl Benz, motorised transport relied on a host of innovations dependent on synthetic chemicals, such as petroleum, a throttle system, spark plugs, gear shifters, and carburetors. Synthetic chemicals in petroleum alone comprise paraffins, cycloparaffins, olefins, and aromatic hydrocarbons, not to mention a whole range of commercially secret additives. Tyres, too, depended on chemical innovation. Although their composition is a commercially protected secret, we know that synthetic tyre chemicals include isoprene, oil, and resin. And while motorised vehicles required petroleum to be refined from crude oil, the asphalt created as a by-product of the refinement process was used to seal further roads that encouraged further vehicle use in a self-fulfilling cycle that saw increased consumption of synthetic chemicals.
Differing from the pre-industrial roads that bore handfuls of vehicles like wooden carts and caravans moving as fast as horses would permit, modern roads can bear the loads of many hundreds of fully laden trucks moving at over one hundred kilometres an hour in almost any weather condition―all enabled via the production of synthetic chemicals. These modern roads and the production of synthetic chemicals that gives rise to them allow for the transport of goods and commodities such as food and clothing in such volumes that without them survival in today’s cities and other permanent settlements would not be possible: there’s just no way large human settlements like cities can be fed and sustained without modern roads and motorised transport ergo, synthetic chemicals. Roads and motorised vehicles have not only enabled but caused a completely new way of life for almost every person on the planet.
And roads are just one example of our chemical dependency: one can go through a similar thought experiment with substances such as plastics and medicines to understand how dependent humans have become on synthetic chemicals. The change in our way of life, from hunter-gatherer and subsistence farming to industrial farming and city living is a regrettable behaviour that has gone hand in hand with the development of synthetic chemical use and impact. Just as today’s cities cannot survive without the agriculture humans sleep-walked into developing thousands of years ago, modern humans cannot survive without the synthetic chemicals developed nearly two hundred years ago.
And so, what to do? Agriculture is well-recognised for its extensive negative impacts to biodiversity and environmental health: it necessarily sees the flourishing of species that can be consumed by humans over those that cannot. With few exceptions, however, humans no longer have the knowledge to consume the native plants and animals that remain on our beautiful Earth. It’s the same with synthetic chemicals; without the roads, we cannot eat; without the plastics, we cannot package the food; without the medicines, we see our children die. We’re locked into chemical dependency, people, and like our dependency on agriculture, the environmental consequences of this dependency are tragic.