Squeaky Wheels
The one thing that the Safety Assessment Paradigm and the
Risk Assessment Paradigm have in common is that they are both mechanisms for making
regulatory decisions. But generally
speaking, they have a different beginning.
A Safety Assessment for a food additive begins with a request for
approval. Minor issues involving
individual consignments of food that are currently being detained by the agency
are a little like that too; either the food will be allowed on the market or it
won’t. But, the bigger problems that
only a risk assessment can deal with begin with an issue that often has an
undetermined solution. New squeaky wheels can
pop up in several different ways:
- Chemistry problems. A contaminant known to be toxic is discovered at concentrations that were previously unknown. The best example of this is acrylamide which, as a result of industrial usage, is known to be neurotoxic and carcinogenic. It turns out that it is often synthesized by cooking food; relatively high levels are found in coffee, french fries, and pretzels.
- Toxicology problems. A chemical that occurs in food is discovered to have potential health effects. This is actually a rare occurrence, and typically only happens when there are health effects in need of explanation. Problems of this sort are far more likely to happen with immediate effects that occur soon after a food is consumed. The discovery over fifty years ago that Minamata disease was attributable to methylmercury in fish is a prime example.
- Hello Again problems. There are a handful of chemicals that are of recurring interest partly because they are known to be toxic, but also because their notoriety stimulates research interest and consumer advocacy. Methylmercury is in this category now, along with arsenic, cadmium, and lead. There are some fungal toxins (e.g. aflatoxin) and industrial chemicals (e.g. dioxins) that belong in this category of issues as well. It is the recurring issues that are in greatest need of quantitative risk assessment. But, for that to happen, the political impediment of the shell game must be overcome.
Managing Exposure By Setting Levels
Food additives and pesticides are introduced into the food supply deliberately. This simple fact means that exposure to them can be, more or less, effectively controlled by setting levels that limit their use. Contaminants, by definition, are not intentionally added. That fact makes them more difficult to avoid. It also means that the federal government has less authority to regulate them than additives or pesticides. But nonetheless, the management technique that is inextricably associated with the safety assessment paradigm is setting a level. And therefore, since safety assessment is a far more familiar way of dealing with chemicals in food, the strategy of first resort for limiting exposure to contaminants is to set a level. Sometimes, that works. For example, consider the distribution of aflatoxin in Illinois corn between 2010 and 2014 (Illinois Dept of Agriculture, 2015):
Aflatoxin Concentration
|
2010
|
2011
|
2012
|
2013
|
2014
|
<5 ppb
|
384
|
387
|
285
|
391
|
392
|
5 to 20 ppb
|
2
|
4
|
40
|
6
|
6
|
20 to 50 ppb
|
9
|
3
|
30
|
4
|
2
|
>50 ppb
|
7
|
3
|
2
|
||
50 to 100 ppb
|
9
|
||||
100 to 200 ppb
|
27
|
||||
200 to 300 ppb
|
8
|
||||
>300 ppb
|
1
|
Even though monitoring aflatoxin concentrations is
difficult, there is a payoff. First,
lots of corn with levels of aflatoxin that may result in acute toxicity
(probably not even with 300 ppb, but it is getting close) will be excluded from
both human and animals food. Second, a
few lots that contribute a high percentage of total average exposure will be
excluded. In particular, the 19% of the
samples in 2012 over the FDA action level of 20 ppb are responsible for about 87% of the
total aflatoxin in the entire set (calculated using median concentrations for each concentration interval).
Not Managing Exposure By Setting Levels
However, when the effect results from long term average exposure,
setting levels often doesn’t really work at all. The overall exposure will reflect the average
concentration in many food items.
Elimination of a few food items with higher concentrations may have
little impact on the average concentration.
If the range of contaminant concentrations are narrow (e.g. like
Illinois corn in 2010. 2011, 2013, or 2014 rather than 2012), the impact is
even more impotent. For example consider
the distribution of arsenic apple juice (from Carrington et al, 2013):
Since there are no apple juice samples with inorganic
arsenic concentrations above 10 parts per billion, any limit that is greater
than 10 will have little or no impact on the average concentration (with a
larger sample size it is likely that there would be some above 10) . A limit of less than 10 will impact the
average concentration somewhat, but the limit could only be achieved by
throwing away large quantities of apple juice.
Arsenic in apple juice is not the only example. As another example where an analysis of the
impact on exposure was conducted, a World Health Organization analysis (JECFA,
2007) concluded that for tree nuts other than pistachios, the presence of any
feasible maximum limit would have little effect on dietary exposure to
aflatoxin. Yet, even when they don’t
work, levels get set anyway. Codex
Alimentarius, the UN body sets food safety standards for international use
routinely sets levels for contaminants after determining that those levels will
have little economic impact.
So, more often than not, even though setting a level gives
the appearance of doing something, it is often the “doing nothing” option in
disguise. There is definitely something
with that, but what it is may be worthy of debate: Either the authorities are not protecting the
public from a risk they need to be protected from, or they are pretending to
protect the public from a risk that isn’t worthy of attention.
References
Carrington CD, Murray C, and Tao, S. (2013). A
Quantitative Assessment of Inorganic Arsenic in Apple Juice.
Illinois Department of Agriculture (2015). Mycotoxin survey.
Joint Expert Committee on Food additive and Contaminants
(2007). Aflatoxins:
Impact of Different Hypothetical Limits for Almonds, Brazil Nuts, Hazel Nuts,
Pistachios and Dried Figs. WHO Food Additive Series 59, pp.
306-356.
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