Which chemical exposure is primarily associated with skin irritation and respiratory distress?

Chlorine exposure is primarily associated with skin irritation and respiratory distress due to its aggressive chemical properties. When chlorine comes into contact with skin, it can cause irritation and even chemical burns, depending on the concentration and duration of exposure. Its gaseous form is also a potent respiratory irritant; inhalation can lead to symptoms such as coughing, difficulty breathing, and throat irritation. These immediate reactions occur because chlorine gas reacts with moisture present in the respiratory tract, forming hydrochloric acid, which can damage the tissues.

In contrast, the other options have different primary effects. For example, carbon monoxide is known for causing systemic issues related to oxygen transport in the blood, primarily affecting the cardiovascular and nervous systems rather than causing skin irritation or respiratory distress in the same way as chlorine. Lead exposure is more related to neurological and developmental effects rather than acute irritation or respiratory issues. Sulfur dioxide, while it can irritate the respiratory system, tends to cause more chronic effects, especially in sensitive individuals, and also can lead to acid formation that may affect the environment and health over time but is not as immediate in terms of skin irritation as chlorine. Thus, chlorine is the clearest choice for causing both skin irritation and respiratory distress.