The Substitution Principle: a case for scepticism?

January 27, 2014 at 8:51 am | Posted in Feature Articles | 1 Comment

Blue edited - Ben Joossen - stock xchng

Campaigns to substitute toxic chemicals for safer alternatives recently received a shot in the arm from new initiatives announced by Walmart and Target (Gunther 2013). Walmart is prioritising 10 problem compounds for phase-out from the goods they sell (Lascher 2013a), while Target is introducing a system for scoring the environmental performance of its range of goods, heavily weighted towards the toxicity of constituent chemicals (Lascher 2013b). The programmes are intended to encourage the suppliers of Target and Walmart to develop greener formulations for their products.

Both of these are examples of the growing popularity and influence of the Substitution Principle, the idea that chemicals which could harm human or environmental health should be replaced with chemicals which are less likely to do so. The Principle can be cast in terms favouring hazard or risk: hazard-oriented interpretations state that chemicals which pose an identifiable hazard (usually toxicity) should be replaced with ones with less or ideally no hazard; risk-oriented interpretations state that one chemical should be replaced with another if the substitute poses less risk of harm.

A hazard-oriented interpretation of the Substitution Principle is a fundamental component of EU REACH regulations. Under REACH the hazard profiles of chemicals are used to generate a list of Substances of Very High Concern, which are subsequently removed from use unless no viable alternative can be found. This process is heavily backed by NGOs, with complaints about substitution typically focusing on the slow pace of progress rather than whether or not particular substitutions have successfully reduced harm done by chemicals to people and the environment (Santos 2013).

Substitution strategies are not, however, as effective as we might want them to be. Recent examples which show problems in the implementation of the Substitution Principle include changes in the flame retardants being detected in house dust and phthalates detected in people. In Germany, a clear trend towards use of novel flame retardants in favour of now-banned PBDEs has been observed, yet insufficient toxicological data exists to allow assessment of possible effects on health (Fromme et al. 2013). In the US, biomonitoring data shows a change in the last 10 years to the phthalates to which people are exposed, away from DEHP and its metabolytes to other less well-studied compounds, in particular diisobutyl phthalate (Zota et al. 2014).

The purpose of implementing the Substitution Principle is to reduce harm from chemicals and lead to a cleaner environment. If this is not being achieved, should implementation of the Principle really be encouraged?

Substitution does not have to be blind

The problems with substituting flame retardants and phthalates are illustrative of a general situation in which problem chemicals are being blindly substituted: hazardous compounds are being identified then replaced by drop-in alternatives, without anyone addressing the toxicity issues which resulted in the substituted chemical being pushed out of the market in the first place.

Substitution does not have to be blind, of course, and there are a number of examples of programmes designed to reduce the odds of making poor substitution decisions. These include the Green Screen, used by Hewlett Packard, Nike and Staples (Green Screen 2014), and the GoodGuide, the database underpinning Target’s new chemicals initiative (GoodGuide 2014).

The Green Screen and GoodGuide grade chemicals and their possible alternatives according to toxic hazard. Users of the systems are supposed to introduce a substitute chemical only if it has a better hazard profile than the one being targeted for removal.

Such a hazard-based approach is not infallible – lack of information or surprising new toxicity findings can result in substitutions which prove to be a reversal rather than an advance in product safety. Perfection, however, is probably not what anyone is aiming for, with even the sceptics of the Substitution Principle likely to agree that we just need to get decisions correct often enough that overall harm from chemicals is reduced.

The sort of informed substitution granted by the GreenScreen and GoodGuide approaches would be an improvement on how substances are classified as SVHCs under REACH and the piecemeal initiatives on phthalates and flame retardants, which identify problems but say nothing about the standards which potential substitutes should meet, therefore allowing bad substitutions all over the place. Sceptics of the Substitution Principle, however, argue that even this sort of improvement would not be enough.

Identifying hazard as only part of the problem

Professor Ragnar Löfstedt, Director of King’s Centre of Risk Management, King’s College London, argues that even if the failures in information requirements which are currently allowing hazardous chemicals being replaced with equally bad or worse alternatives were to be solved, there would still be fatal flaws in the Substitution Principle as currently implemented.

As he sees it, the Substitution Principle cannot work because it is too hazard-oriented because substituting one chemical for another does not necessarily lead to a reduction in risk, even if the substitute genuinely represents a reduction in hazard (Löfstedt 2013, Löfstedt 2014).

The point here is that because chemicals present many different hazards besides toxicity, not all of which increase in step with each other, each of these hazards needs to be assessed for relative likelihood and quantity of harm before a rational decision to favour one chemical over another can be made.

An example Löfstedt uses is the removal of lead from solder, which improves environmental performance but increases the risk of electronics failure from solder whiskers and fracture. He argues that the decision to remove lead from solder on the basis of the neurological hazard it presents simply resulted in other risks being introduced by the alternatives. This left it down to luck that the substitution of lead did not do more harm than good.

Löfstedt’s position, therefore, is that prevention of harm by substituting one chemical for another requires a full risk assessment of each alternative across all hazards, rather than focusing on one particular hazard (such as toxicity) at the expense of others. Until society has developed a working, risk-based approach to substitution, implementation of the Substitution Principle should be put on hold; effectively, a moratorium on the Principle.

Is a moratorium on substitution really the answer?

Currently, the toxicity-focused, hazard-based approach is the one which is legally mandated within REACH. Calls for a moratorium on substitution measures are based on the belief that halting this strategy in favour of a broader risk-balancing approach will yield better results. But will it?

The principle obstacle to success in substitution, whether risk- or hazard-based, is lack of toxicity data about the compounds we have in our chemical library. We have insufficient data to reliably characterise the hazards posed by alternatives to current problem chemicals; risk-based approaches requiring the same hazard data plus accurate exposure scenarios might in the long term yield better results, but for now they fall down at the same hurdle as the hazard-based approaches.

The Swedish Chemicals Inspectorate (KEMI) argues that instead of encouraging bad decision-making, substitution targets are actually an important part of generating the data needed to improve the safety of chemicals in consumer goods. In discussing a ban on BPA in receipt paper, KEMI says that even if obvious safer alternatives do not yet exist, a substitution deadline encourages manufacturers to produce data on a compound and its alternatives, allowing an informed choice about substitutes to be made (KEMI 2012, see also H&E #51: Alternatives to BPA in Receipts).

Toxicity as a design feature

Putting a sunset date on a chemical runs the risk of manufacturers choosing the next closest molecule and dropping it into a product in place of the restricted chemical – the blind substitution we are trying to avoid. Prevention of blind substitution requires a minimum standard for an alternative and ensuring there is sufficient expertise to produce a compound which meets this standard: a standard has to be set and designed towards.

Standards are nothing new in product design, nor are the complex challenges and trade-offs in formulating products which meet multitudinous performance and price requirements. Designing around a particular toxicological profile is no different in principle to any other feature; the only difference is that it is a new consideration, brought into particularly sharp focus by current regulatory priorities relating to chemical toxicity.

This makes green chemistry, with its focus on the design of benign molecules, a vital component of a functioning substitution programme. Building capacity in green chemistry and developing an understanding of how to design for environmental as well as other risks is, however, a job which does not necessarily have to be done at the same time as identifying the compounds which may be problematic.

The issue with substitution then becomes one of whether or not we can accept a temporary status quo of an incomplete solution, in which chemicals are introduced to products in spite of not being demonstrably better, so long as the eventual outcome is that substitution is effective? If we can, then rather than bringing a halt to the one part of the system which is working (identifying problem compounds), we can focus our energies on developing the necessary techniques for including the toxicological profile of chemicals in the design process in order to meet environmental objectives in product design.

The alternative is to hold that only an all-or-nothing approach to implementing substitution will do, that a temporary status quo where we get one part of the system working while developing the rest is unacceptable. The question then, however, is how we get any sort of substitution process started? If we stop listing problem compounds, we stop identifying chemicals for which substitutes need to be found, and we stop enforcing change in the chemicals which are being used in consumer goods, how do chemicals with poor environmental performance even become a problem? This seems to be a question which needs to be answered by those in favour of a moratorium on the Substitution Principle.

1 Comment »

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  1. An interesting post–but it needs to be edited! The language about substitution is backwards. Nobody is trying “to substitute toxic chemicals for safer alternatives;” it’s the reverse the author means to discuss!


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