Good afternoon. My name is Dr. Yvona Buczek, and I'm honoured to have the opportunity to appear before this committee. I'm an assistant section head in the toxicology section, Centre of Forensic Sciences in Toronto, which I will refer to as the CFS.
I'm accompanied today by my colleague, Dr. Marc Pelletier, who is an experienced scientist from our section.
The CFS is a provincial forensic science laboratory in the public safety division of the Ministry of Community Safety and Correctional Services. We provide forensic science services to all official investigative agencies in Ontario.
Much of our work in the toxicology section concerns impaired driving. We train police officers in Ontario in the theory and operation of approved screening devices and evidential breath-testing instruments. We attend court regularly to provide scientific evidence regarding the pharmacology of alcohol impairment and provide calculations of blood alcohol concentrations, or BAC.
I hope the information I present today will be of assistance to the committee.
The operation of a motor vehicle requires the coordinated functioning of a variety of sensory, motor, and intellectual faculties, including divided attention, awareness of one's surroundings, choice reaction time, time to respond to complex driving situations, judgment of speed and distance, risk assessment, vigilance, being alert for extended periods of time, and vision.
The degree of impairment produced by alcohol is dependent upon BAC. Whether impairment is demonstrable depends on the complexity of the driving task. For example, the impairing effects of alcohol are evident in driving situations that are unpredictable and that require a rapid and appropriate response. Under controlled, experimental conditions, impairment of divided attention tasks has been reported at BACs as low as 15 milligrams of alcohol in 100 millilitres of blood. Nevertheless, based on a critical review of the relevant scientific literature, it is my opinion that impairment with respect to driving becomes significant at a BAC of 50 milligrams of alcohol in 100 millilitres of blood and increases from then onward. Impairment may occur in the absence of visible signs of intoxication, which may be due to tolerance.
Alcohol is a small, simple molecule. Relative to other drugs, alcohol produces predictable effects on the body. The effects produced by alcohol in the human body—that is, observable signs of intoxication—are dependent on BAC. The magnitude of the effects increases as BAC increases.
I will now describe the signs of intoxication that would be expected within a wide range of BACs in the light-to-moderate drinker. Please note that in individuals who frequently consume large quantities of alcohol, some effects are diminished due to tolerance. A tolerant individual might not display any observable signs of intoxication, even in the presence of a high BAC level.
At concentrations ranging between zero to 50 milligrams of alcohol in 100 millilitres of blood, while signs of intoxication are absent or slight, information processing is slower. Observable signs might include mild euphoria and lack of inhibitions in a social setting—for example, talking loudly.
At the range between 50 and 100, intoxication is more likely, and might include some degree of motor incoordination, particularly of fine motor skills. There is increased loss of social inhibition—for example, increase of confidence and impaired judgment.
At the range between 100 and 200, intoxication is very apparent due to a decrease in motor coordination, such as slurred speech, staggered walk, inappropriate or sudden changes in mood, and drowsiness.
At 200 and greater, intoxication is very apparent because of increased central nervous system depression, which may include confusion, significant loss of motor control, nausea and vomiting, and varying degrees of sedation up to and including loss of consciousness.
At 300 and greater, intoxication is even more pronounced due to significantly increased central nervous system depression. The general anesthetic properties of alcohol are evident and might result in coma.
At 350 and greater, intoxication might result in death due to respiratory depression.
Scientifically, impairment can be distinguished from intoxication. I define impairment as the diminished ability to operate a motor vehicle. Studies utilizing low BACs have demonstrated impairment at levels much lower than was previously considered to be the threshold.
A review of the scientific literature on this subject can be crystallized in the following two points. One, as the BAC increases, the degree of impairment increases. Whether impairment is observable depends upon the complexity of the task. In an impaired person, impairment might not be observable in the routine driving task, but would be obvious in driving situations requiring a rapid response.
I shall now present a number of key points from the relevant scientific literature. References are available.
Under controlled experimental conditions, it has been demonstrated that repeated performance in certain tasks while under the influence of alcohol might make a subject less sensitive to the effects of alcohol. This is called functional tolerance. Many adults operate motor vehicles on a daily basis. However, driving is largely resistant to functional tolerance due to its complex intellectual demands. While at high BACs tolerance may reduce signs of intoxication, impairment is still present.
The most that can be said is that at moderate BACs, between 50 and 70, more-frequent drinkers appear to be less affected and at low risk of accident involvement. At higher BACs, the risk of an accident and the impairment of driving ability are both significantly increased in all drinking frequency groups. While habitual binge drinkers demonstrate similar alcohol-induced behaviour impairment, they have less awareness of impairment when compared to lighter-drinking counterparts. They may have false beliefs in their functional tolerance. That is, although their driving was impaired, they maintained the belief that their performance had actually improved.
There is some scientific evidence that supports the concept of functional tolerance, but only at low to moderate BACs and in simple predictable driving tasks. However, it is highly unlikely that functional tolerance can alleviate the impairing effects of alcohol when the driving task is complex or unpredictable.
Laboratory studies have consistently identified divided attention and choice reaction time as being particularly sensitive to the effects of alcohol, and the impairment is evident at less than 50 milligrams of alcohol in 100 millilitres of blood. Studies assessing the impairment effects of alcohol—