Chlorchemie – The Bad Business of Halogenated Organic Substances

This post is derived from a fact sheet for ÖkoVision, an investment fund or mutual trust investing in companies that, with their policies, busi­ness model, processes, products and services, are likely to succeed in an equitable and sustainable future industrial society and market economy.

Companies are not compatible with ÖkoVision if they produce, promote, trade, distribute, use (in significant quantities), or enable or promote the manufacture, trade, or use of halogenated organic substances.

As a principle, ÖkoVision does not invest in such companies.  The criterion is very important but not absolute, and attenuating circumstances are considered in judging businesses (see below for detail).

The criterion is about organic chemical substances or compounds, in which one halogen atom or several same or different halogen atoms form direct bonds with carbon.  Of concern are mass products of the chemical industry, such as PVC or halogenated solvents, and specialized chemicals, such as pesticides or biocides.  The criterion does not apply to pharmaceutical and other substances that produce large benefits with the use of small quantities, and for which no practical substitutes exist. 

Reasoning:

In chlorine chemistry ("Chlorchemie") or more widely "halogen-organic chemistry", substances are produced or used, in which a chemical bond exists between halogen atoms – fluorine, chlorine, bromine, or iodine – and carbon atoms.  All substances with a halogen-carbon bond and/or their biochemical or physical metabolites and degradation products are highly toxic, eco-toxic, carcinogenic, teratogenic, act as greenhouse gases and aggravate climate change and/or are damaging to the Earth‘s protective ozone layer. 

While some substances can be used in small quantities in medicine, where the benefits for humans outweigh the costs and damages, most such substances are so harmful in their manufacture, use, and disposal that cost-benefit assessments should stop their production, sale and trade.  Even if some halogenated organic substances are not hazardous per se, they become so when they react or degrade, for instance when incinerated, exposed to light or natural ultraviolet rays (in the strato­sphere).  The production of halogenated organic substances is hazardous; notorious large accidents in the chemical industry, such as at Bhopal, Schweizerhalle (Sandoz), or Toulouse, involve, as a rule, this class of chemicals.  Chlorine chemistry is an obstacle to the development of a sustainable and ethical industrial society and market economy. 

Chemical Background:

Halogens, the elements "born from salt" or "forming salt", form a group in chemistry‘s periodic table: Fluorine (F – no. 9 in periodic table), chlorine (Cl – 17), bromine (Br – 35) and iodine (I – 53)[1].

Their high chemical bond energy (or electronegativity or redox potential) is the key characteristic of halogens.  Fluorine has the highest chemical bond energy of all elements[2], and bond energy declines within the group from fluorine to iodine.  Each atom is lacking one electron in its outermost shell; they strongly seek to gain one electron and complete that shell (which charges them negatively or reduces them).  This characteristic makes elemental halogens extremely reactive; they can break up many chemical compounds and form new ones with particular properties of concern.  Some of the newly formed compounds are themselves very stable, while others are not.

Chemical Policy Background:

"Chlorchemie" symbolises a chemical policy controversy, at the heart of which are the manufacture, use, recycling (or better "down-cycling") and the (highly problematical) disposal of polyvinylchloride (PVC) and other mass or bulk products of the chlorine chemical industry.  Ozone-depleting chlorinat­ed or halogenated hydrocarbons are also part of the controversy.  There are also a range of sub­stances for special purposes as industrial chemicals or, for instance, as insecticides or fungicides.

It is known since 1885/1890 how pure chlorine on the one side and on the other potassium or sodium hydroxide can be produced using electrical energy (chloralkali electrolysis), where chlorine and potas­sium viz. sodium are always produced in fixed proportion (combined production).  The objective was (and to a degree still is) the production of potassium and sodium; chlorine emerges as a dangerous by-product (or waste), which has to be chemically bonded and stabilised before it could be disposed of (in landfills).  This was done by bonding of chlorine as chloroethene or vinyl chloride (C₂H₃Cl), which was then used to synthesise long-chained polyvinylchloride (PVC [C₂H₃Cl]_n) for landfilling.  PVC is still quite unstable, and in its decay releases the aggressive and corrosive chlorine.  For this reason, PVC was further stabilised with additives such as cadmium, and through the addition of plasticisers, such as a partly endocrine phthalates, was given properties that allowed PVC to be sold as a product.

The generation of combined products and by-products is a common feature of the chemical industry.  Not all such products can be put to good use.  Often the exact composition of mixtures of such pro­ducts is not known, and the separation of mixtures would be too cumbersome and expensive.  In such cases, initially in the interest of plant safety, mixtures with unknown or uncertain composition and characteristics were "fully chlorinated" or "fully halogenated" and thus homogenised.  This method of waste treatment produces large quantities of mostly short-chained halogenated alkanes[3], the fluoro-chloro-hydrocarbons (CFC), which have known properties and could be marketed as solvents, cooling agents, or propellants for spray cans, for instance.  Fully halogenated hydrocarbons are chemically very stable, no longer reactive, and thus very durable.  However, they rise to the stratosphere where they decay under the exposure to high-energy radiation from space and then damage the Earth‘s stratospheric ozone layer that protects life from the radiation. 

Chlorine chemistry is a history of converting hazardous waste into hazardous yet marketable products. 

Another aspect drives the continuing chemical policy controversy in addition to the history and the dangerous properties of the products of the chlorine chemical industry:  The production of chlorine and other halogens as feed-stock for the halogen-organic chemical industry requires enormous quantities of electrical energy.  For this reason, chloralkali electrolysis plants and nuclear power plants are found next to one another, with the chemical industry benefitting more or less directly from the subsidies and privileges given to nuclear power plants. 

The "Dirty Dozen" and the "Nasty Nine":

Chlorine and other halogens are prominent also in the "Dirty Dozen" and "Nasty Nine" regulated (or banned) by the Stockholm Convention. These are "persistent organic pollutants" or "POPs", namely dangerous insecticides, a fungicide, industrial chemicals and pollutants from combustion plants.

What this is not about:

The chemical bonds between halogens and carbon are at the core.  Chemical bonds with other elements of the carbon group or metals are not relevant here.  Not part of the controversy and thus not in focus here are inorganic halogen bonds, mostly salts.  Sodium chloride (NaCl) is cooking salt and on everyone‘s lips, and the halogens are important for human health (fluorine for teeth, iodine for the thyroid gland, …).  Industry lobbyists like to stress that "chlorine is not dangerous", as it is part of food.  The argument is designed to distract from the dangers cause by halogen-organic compounds.

Halogens also form bonds with other elements that are similar to carbon.  An example is silicon, and silicon chloride plays a role in semiconductors and the production of solar panels.  Although such compounds can be problematic, they are not part of the chlorine chemistry controversy. 

---

[1]         There is also the rare, radioactive astatine (At – 85) and the artificial or man-made and highly unstable ununseptium (Uus – 117).  These are without practical relevance here.

[2]         As a consequence, no other chemical element can break the chemical bonds formed by fluorine, and physical energy in the form of electricity must be used to form pure fluorine (F₂); producing meaningful quantities of pure halogens requires energy-intensive technical processes at industrial scale.

[3]         Alkanes are chains of carbon atoms, which in their basic form are surrounded only by hydrogen (hydro­carbons); methane (CH₄) and ethane (C₂H₆) are most relevant here.